Plumbing Terms: A Glossary of Industry Lingo + Detailed Definitions

As a new plumbing pro, entering an industry with its own unique set of terms, slang words, abbreviations, and acronyms can be overwhelming. 

From measurements and product labels to unfamiliar terms exchanged between seasoned plumbing techs, it takes time to be well-versed in plumbing terms… unless you have a handy guide to speed up the learning process. 

Fortunately, we’ve compiled all the essential plumbing terms and definitions in one simple guide. You can refer back to this list each time a new word or plumbing slang term leaves you scratching your head. 

Let’s get started…

Essential Plumbing Terms and Definitions

Access Panel: A removable cover that provides access to plumbing fixtures for maintenance or repair. Commonly found behind showers, tubs, or under sinks.

Absorption Field: A system of trenches filled with gravel or sand where wastewater is dispersed after leaving a septic tank. Ensures that treated water is safely absorbed into the ground.

Acrylic: A durable, synthetic material used in plumbing fixtures like tubs, sinks, and shower enclosures. Resists chipping and fading.

Activated Carbon: A porous material used in water filtration systems to remove contaminants, odors, and impurities from water.

Adaptor: A fitting that connects pipes of different sizes or materials. Used to join copper to PVC, PEX to CPVC, etc.

Aerator: A screen attached to the end of a faucet to control water flow and reduce splashing while conserving water.

Air Admittance Valve: A one-way valve that allows air to enter a drainage system to prevent siphoning without venting through the roof.

Air Chambers: Vertical pipes installed near faucets to absorb water hammer shocks, preventing pipe damage.

Air Gap: A physical space between a water outlet and a drain to prevent backflow and contamination.

Air Lock: A blockage caused by trapped air in a pipe, preventing proper water flow. Common after repairs or new installations.

Angle Stop: A shut-off valve located at the connection between a water supply line and a plumbing fixture, like a sink or toilet.

Angular Discharge Tube: A pipe designed to direct water at a specific angle, often used in drainage systems to control flow direction.

Anode Rod: A sacrificial metal rod placed in water heaters to prevent tank corrosion by attracting corrosive elements.

Anti-Scald Valve: A valve that regulates water temperature to prevent scalding by mixing hot and cold water.

Anti-Siphon: A device that prevents backflow by breaking the siphon effect, protecting potable water from contamination.

Automatic Compensating Valve: A valve that maintains consistent water temperature by adjusting the mix of hot and cold water despite pressure changes.

Back Pressure: The resistance or pressure that opposes the flow of water in a plumbing system, potentially causing backflow.

Backflow: The reverse flow of contaminated water into clean water lines, prevented by backflow prevention devices.

Backflow Preventer/Prevention Device: A valve or assembly that prevents backflow, ensuring contaminated water doesn’t enter the potable water system.

Back Flush: The process of reversing the water flow to clear out debris or contaminants from a plumbing system.

Backup: A blockage or clog that prevents wastewater from draining, causing water to back up in sinks, toilets, or tubs.

Backwash: A process of reversing the flow of water through a filter to flush out trapped debris, commonly used in water softeners and pool systems.

Backwater Valve: A valve installed in a drain line to prevent sewage from backing up into a building. Essential for preventing basement flooding during heavy rains.

Ball Passage: The diameter of a toilet’s trapway, indicating the size of waste that can pass through. Larger ball passages reduce clogs.

Ball Valve: A valve with a spherical disc that controls water flow. Offers quick shut-off capabilities and is commonly used in main water lines.

Basin: A plumbing fixture used for washing, such as a bathroom sink. Can be wall-mounted, pedestal, or under-mounted.

Basin Wrench: A specialized wrench designed to tighten or loosen nuts on sink faucets in tight spaces. Features a pivoting jaw.

Basket Strainer: A mesh insert that fits into a sink drain to catch debris and prevent clogs. Common in kitchen sinks.

Bidet: A plumbing fixture designed for washing the genital and anal areas. Typically installed alongside toilets or integrated into toilet seats.

Bisque: A pale, off-white color commonly used to describe sinks, toilets, and bathtubs. Provides a neutral, timeless look.

Black Water: Wastewater containing human waste, often requiring treatment before disposal. Distinguished from gray water.

Bleed: The process of releasing air or excess water from a pipe or valve to prevent pressure build-up.

Boiler: A heating system that uses hot water or steam to provide warmth to a building. Can also provide hot water for fixtures.

Boiling Point: The temperature at which water turns to steam, typically 212°F (100°C) at sea level.

Branch: A secondary line that carries water to a specific fixture or appliance. Branch lines connect to the main line.

Branch Line: A water supply or drainage pipe that connects to a main line. Delivers water to individual fixtures.

Branch Vent: A vent line connected to a branch drain that allows air to circulate, preventing sewer gases from entering the building.

Brass: A corrosion-resistant metal alloy made of copper and zinc, commonly used for valves, fittings, and pipe connectors.

Building Drain: The lowest horizontal pipe in a plumbing system that collects wastewater from all fixtures and carries it to the sewer line.

Burner: A component of a water heater or boiler that ignites fuel to generate heat, raising the temperature of water in the tank.

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Catch Basin: A receptacle designed to collect and manage stormwater runoff, typically found in parking lots or low-lying areas.

Centerset: A type of faucet with a spout and two handles mounted on a base plate. Designed for sinks with three holes spaced 4 inches apart.

Check Valve: A valve that allows water to flow in only one direction, preventing backflow. Commonly used in sump pumps and well systems.

China: A durable, non-porous material used to manufacture sinks, toilets, and other plumbing fixtures. Typically coated with a glossy enamel finish.

Chloramines: A disinfectant made of chlorine and ammonia, often added to public water supplies to kill bacteria. Can cause corrosion in older plumbing systems.

Chlorine: A chemical used to disinfect water supplies, preventing the spread of waterborne diseases. Excessive chlorine can damage rubber seals in plumbing.

Circuit Vent: A vent that serves multiple fixtures on the same drain line, preventing siphoning and promoting proper drainage.

Cleanout: An access point in a drainage pipe that allows plumbers to clear clogs and inspect the plumbing system. Typically capped and located at ground level or outside the building.

Cleanout Plug: A removable cap or cover that seals a cleanout opening, preventing debris from entering the drainage system.

Clevis Hanger: A metal hanger used to support horizontal pipes, allowing them to move slightly to prevent stress and damage.

Close-Coupled Toilet: A toilet design where the tank and bowl are bolted together as a single unit, saving space and simplifying installation.

Closed System: A plumbing system in which water is recirculated and reused, minimizing water waste. Common in hydronic heating systems.

Closet: A plumbing term for a toilet. Commonly referred to as a water closet (WC).

Closet Auger: A specialized tool used to clear toilet clogs. Features a long, flexible cable with a curved end to navigate toilet traps.

Closet Bend: A curved fitting that connects a toilet’s waste outlet to the drain line. Allows waste to pass through at a 90-degree angle.

Closet Flange: A fitting that secures the toilet to the floor and connects it to the drain line. Also known as a toilet flange.

Combination Waste and Vent: A plumbing configuration where a single pipe functions as both a drain and a vent. Common in kitchen sink setups.

Commode: A portable toilet or a toilet fixture. The term is sometimes used to describe toilet seats or specialized seating devices.

Common Vent: A vent that serves more than one fixture, allowing air to circulate and preventing siphoning of traps.

Compression Fitting: A plumbing connection that uses a metal or plastic ring (ferrule) to seal the joint when tightened. Used in pipes and tubing.

Console Lav: A bathroom sink that is mounted on legs or brackets rather than a cabinet base. Adds an open, airy look while maintaining function.

Copper: A durable metal commonly used for water pipes due to its corrosion resistance and longevity. Available in rigid and flexible types.

Copper Pipe (Types M, L, K): M, L, and K are grades of copper pipe. M is the thinnest, L is medium thickness, and K is the thickest. L is common in residential plumbing.

Coupling: A short fitting that connects two pieces of pipe, allowing them to function as a single length. Comes in threaded or slip-joint designs.

Cross Connection: A point where potable water connects to a non-potable source, posing a contamination risk. Managed through backflow prevention devices.

Culvert: A drainage pipe that directs stormwater away from roads and buildings, preventing erosion and flooding.

Cycle Time: The duration a water heater or pump takes to complete one full heating or pumping cycle. Helps in calculating efficiency.

Dam: A raised edge or barrier that directs water flow in fixtures like sinks or showers, preventing overflow.

Degree Rise: The temperature increase in water as it passes through a heater. Indicates the heater’s capacity to warm water quickly.

Desanco Fitting: A connector that adapts drainage pipes to different sizes or materials, typically found under sinks.

Diaphragm: A flexible membrane inside valves or pumps that responds to pressure changes, controlling flow or preventing leaks.

Dielectric Union: A fitting that prevents electrolysis between dissimilar metals (e.g., copper and galvanized steel), reducing corrosion.

Dip Tube: A pipe inside a water heater that directs incoming cold water to the bottom, ensuring even heating.

Discharge Tube: A pipe that channels water from a valve or pump to a drainage point. Common in water heaters and sump pumps.

Dishwasher Tailpiece: A vertical pipe extension that connects a dishwasher’s drain to the sink’s waste line, preventing backflow.

Disposal Field: An area of soil where wastewater from a septic tank is absorbed and filtered. Also known as a leach field.

Diverter Valve: A valve that directs water flow to different fixtures, such as switching water from a tub spout to a showerhead.

Double Wye: A Y-shaped fitting with two branches at 45° angles, allowing multiple connections in a drainage system.

Drain: A pipe or opening that removes wastewater from sinks, showers, or toilets, directing it to the sewer or septic system.

Drain Valve: A valve that releases water from a system for maintenance or winterization. Often found in water heaters.

Drip Leg: A capped vertical pipe installed in gas lines to collect moisture or debris, preventing blockages in the main line.

Dual Element Heater: A water heater with two heating elements – one at the top and one at the bottom – providing more efficient heating.

Dual-Flush: A toilet with two flush options: a low-volume flush for liquid waste and a higher-volume flush for solid waste, conserving water.

Dynamic Pressure: The pressure of flowing water within a plumbing system, as opposed to static pressure, which is measured when water is not flowing.

Efficiency: A measure of how effectively a water heater or plumbing fixture uses energy to perform its function, such as heating water or flushing waste.

Effluent: Treated wastewater that flows out of a septic tank, sewage treatment plant, or drainage system.

Elbow (90°/45°): A pipe fitting that allows water to change direction by 90° or 45°, directing flow around corners or obstacles.

Enamel: A hard, glossy coating applied to metal, porcelain, or fiberglass plumbing fixtures for added protection and visual appeal.

Energy Guide Label: A standardized label that displays the estimated annual energy consumption and operating cost of water heaters, dishwashers, and other appliances.

Escutcheon: A decorative plate that covers plumbing penetrations in walls or floors, such as around shower arms or faucets.

Fiberglass: A lightweight, durable material used to reinforce plumbing fixtures, such as tubs and showers, offering resistance to cracking and chipping.

Expansion Tank: A small tank installed in a plumbing system to absorb excess pressure caused by thermal expansion in a closed water heating system.

Fall/Flow: The slope or angle of a drainage pipe that ensures wastewater flows toward the main sewer line without pooling or backflow.

Faucet Seat: The flat surface inside a faucet where the washer seals against to stop water flow. A worn seat can cause leaks.

Female Fitting: A pipe or fitting with internal threads that receives a male-threaded pipe or fitting to create a connection.

First Hour Delivery (Rating): The amount of hot water a water heater can deliver in one hour, indicating the unit’s capacity to meet peak demand.

Fitting; A plumbing component used to connect, redirect, or terminate pipes, such as elbows, tees, and couplings.

Fixture: Any device that draws water from a plumbing system, such as a faucet, toilet, or showerhead.

Flapper: A rubber or plastic valve inside a toilet tank that lifts to allow water to flush and closes to refill the tank.

Flapper Valve: A valve that controls the release of water in a toilet tank. Worn or misaligned flapper valves are a common cause of leaks.

Float Ball: A buoyant ball inside a toilet tank that rises and falls with the water level, signaling the fill valve to open or close.

Float Valve: A valve controlled by a float ball, used to regulate water levels in toilet tanks and water storage tanks.

Flood Level Rim: The top edge of a plumbing fixture where water will overflow if the drain is blocked. Ensures that water doesn’t backflow into the fixture.

Floor Flange: A plumbing fitting that connects a toilet or other fixture to the drain line, anchoring it securely to the floor. Also known as a closet flange.

Flow Control Valve: A valve that regulates the volume of water flow to a fixture or appliance. Common in showers to control pressure and temperature.

Flow Rate: The volume of water that passes through a fixture or pipe in a specific time, usually measured in gallons per minute (GPM).

Flue: A pipe or duct that vents exhaust gases from a water heater, furnace, or boiler to the outside. Prevents dangerous gases from accumulating indoors.

Flue Baffle: A metal plate inside a water heater flue that directs exhaust gases, improving heat transfer and efficiency.

Flue Damper: A device installed in a flue to control airflow and prevent heat loss when the appliance is not operating.

Flush Valve: A valve in a toilet tank that releases water to flush the bowl. Includes components like the flapper and overflow tube.

Flushometer: A valve that uses water pressure to flush a toilet or urinal without a tank, commonly seen in commercial restrooms.

Flushometer Tank System: A system that combines a flushometer with a small storage tank, providing pressure-assisted flushing.

Flux: A paste applied to copper pipes before soldering to prevent oxidation and ensure a strong, leak-free joint.

Foam Insulation: A protective layer applied to pipes to prevent freezing and reduce heat loss, commonly made of rubber or polyethylene.

French Drain: A trench filled with gravel or rock and a perforated pipe that directs surface water away from foundations to prevent flooding.

Friction Loss: The reduction in water pressure caused by the friction between water and the interior surface of pipes, fittings, and valves.

Galvanic Action: A chemical reaction that occurs when dissimilar metals come into contact in the presence of water, causing corrosion.

Gas Cock: A manual valve that controls the flow of natural gas to appliances like water heaters and stoves.

Gate Diverter: A valve that diverts water from one pipe to another, commonly used in tub/shower systems to switch between outlets.

Gate Valve: A valve that uses a flat gate to open or close water flow completely, typically used for main water shut-off points.

Grain Capacity: A measure of how much hardness minerals (like calcium and magnesium) a water softener can remove before needing regeneration.

Gravity Operated Toilet: A toilet that uses gravity and water weight to flush waste, as opposed to pressure-assisted or vacuum systems.

Gray Water: Wastewater from sinks, showers, and laundry that can be reused for irrigation or flushing toilets. Excludes sewage and black water.

Grease Trap: A device that intercepts grease and oil from wastewater before it enters the main sewer line, preventing clogs.

Handshower: A detachable showerhead connected by a flexible hose, allowing users to direct water flow for washing or rinsing.

Head Loss: The reduction in water pressure caused by friction, fittings, and elevation changes in a plumbing system.

Heat Trap: A device or design feature that prevents unwanted heat loss in water heaters by restricting the flow of hot water.

Horizontal Branch: A horizontal drainpipe that collects wastewater from multiple fixtures and directs it to the main stack.

Horizontal Run: The horizontal section of a pipe, measured in feet, that transports water or waste in a plumbing system.

Hose Bibb: An outdoor faucet designed for connecting garden hoses, also known as a spigot or sillcock.

Hot Water: Water that has been heated to a specified temperature, typically between 120–140°F for residential use.

Hot Water Recirculating Pump: A pump that circulates hot water through the pipes to reduce wait time for hot water at fixtures.

House Trap: A U-shaped pipe installed in the main drain line to prevent sewer gases from entering the home.

Hubless (No-Hub): A type of plumbing pipe and fitting system that uses clamps instead of hubs to connect pipes, common in cast iron piping systems.

Hydronic: A heating system that uses water or steam to transfer heat through pipes, radiators, or baseboards.

Hydrostatic Test: A test in which pipes or tanks are filled with water and pressurized to check for leaks or structural integrity.

Indirect Wastes: Wastewater that discharges into a plumbing system through an air gap, preventing backflow and contamination.

Instantaneous Water Heater: A water heater that heats water on demand without using a storage tank. Also known as a tankless water heater.

Insulation Sleeve: A foam or rubber sleeve placed over pipes to prevent freezing and reduce heat loss.

Interceptor: A plumbing device that separates contaminants (like grease, oil, or sand) from wastewater before it enters the main sewer line.

Jet: A small nozzle or opening that directs water flow in fixtures like toilets or spa tubs to provide targeted pressure.

Johnni-bolts: Specialized bolts used to secure a toilet to the floor flange. Designed for easy installation and removal.

Junction Box: A protective housing for electrical connections in plumbing-related areas, such as for water heaters or sump pumps.

Kafer Fitting: A type of pipe fitting with multiple outlets, used to connect various plumbing lines in a compact space.

Knockout Plug: A removable plug that allows for future pipe connections in fittings, drainpipes, or fixtures.

Lavatory: A bathroom sink typically used for handwashing. May be wall-mounted, pedestal, or part of a vanity.

Leach: The process of water seeping through soil, gravel, or sand in a drainage field, allowing wastewater to be filtered naturally.

Leach Field: An area where wastewater from a septic tank is dispersed and filtered through the soil, preventing groundwater contamination.

Lead: A toxic heavy metal historically used in pipes and solder. Modern plumbing regulations prohibit its use in potable water systems.

Leader: A vertical pipe that directs stormwater runoff from gutters to the ground or a drainage system.

Lead-free: A plumbing designation indicating that pipes, fittings, or fixtures contain less than 0.25% lead content, meeting modern safety standards.

Lock Nut: A threaded nut used to secure plumbing components in place, preventing accidental loosening or leakage.

Low-flow: A designation for plumbing fixtures, such as toilets and faucets, that use less water than standard models to conserve water.

Main Line: The primary water supply or drainage pipe in a plumbing system that distributes water or carries wastewater to the municipal system.

Main Vent: A vertical pipe that allows sewer gases to escape from the drainage system while maintaining air pressure to prevent trap siphoning.

Male Thread: A pipe or fitting with external threads that screw into a female-threaded fitting to create a secure connection.

Malleable Fittings: Plumbing fittings made of malleable iron that can be easily shaped or bent without breaking, ideal for gas and water lines.

Manifold: A distribution component that divides a main supply line into multiple branches, often used in PEX or radiant heating systems.

Micron Rating: A measurement indicating the size of particles a filter can remove from water, with lower numbers capturing smaller particles.

Mixing Valve: A valve that blends hot and cold water to maintain a consistent temperature, commonly found in showers and sinks.

MaP Testing: Maximum Performance (MaP) testing measures the flushing capacity of toilets to determine how effectively they clear waste.

Metered Toilets: Commercial-grade toilets that dispense a specific amount of water per flush, conserving water and reducing costs.

Mini-Widespread: A type of faucet with three separate components (spout and two handles) that fits on sinks with 4-inch spacing.

Mixing Valve: A valve that blends hot and cold water to maintain a consistent temperature, commonly found in showers and sinks.

Multi-Stage Pump: A pump that uses multiple impellers to increase pressure and water flow, often used in water booster systems.

Natural Gas: A fossil fuel used to power water heaters, boilers, and other plumbing appliances. Requires specific gas-rated fittings and valves.

Net Usable BTU: The actual amount of heat delivered by a water heater after accounting for heat losses, expressed in British Thermal Units (BTUs).

No-Hub Connector: A plumbing fitting that connects sections of cast iron pipe without hubs using a rubber sleeve and metal clamps.

O-Ring: A circular rubber seal used to prevent leaks at joints and connections in plumbing fixtures and fittings.

Oakum: A fibrous material soaked in tar, used to seal joints in cast iron pipes to prevent leaks.

One-Piece Toilet: A toilet in which the tank and bowl are molded as a single unit, making it easier to clean and maintain.

Outlet Sewer: A pipe that directs wastewater from a building to the municipal sewer line or septic system.

Ovality: A measure of how round or out-of-round a pipe is, impacting the effectiveness of pipe fittings and seals.

Overflow Tube: A tube inside a toilet tank that prevents overflow by directing excess water into the bowl.

Packing: A material used to seal valve stems and other fittings to prevent leaks. Commonly made of rubber, Teflon, or graphite.

Packing Nut: A nut that compresses packing material to create a watertight seal around a valve stem.

Parts Per Million (ppm): A measurement of the concentration of dissolved substances in water, used to determine water quality and hardness.

Peak Hour Demand: The maximum volume of water a plumbing system uses during its busiest hour, influencing pipe sizing and water heater capacity.

Peak Load Period: The time of day when water usage is at its highest, typically in the morning or evening in residential settings.

pH: A measure of water acidity or alkalinity, with a neutral pH of 7. Lower values indicate acidity, higher values indicate alkalinity.

Pilot: A small gas flame in water heaters and boilers that ignites the main burner when heat is required.

Pipe Dope: A paste applied to threaded pipe connections to seal joints and prevent leaks. Also known as pipe sealant.

Pipes: Tubes used to convey water, gas, or waste in a plumbing system. Made from materials like copper, PVC, PEX, and galvanized steel.

Pitch: The slope of a drain pipe, allowing wastewater to flow downhill toward the main sewer line.

Plumb: A vertical alignment that is perfectly straight and level, ensuring proper water flow and structural integrity.

Plumber’s Putty: A malleable sealant used to seal sinks, drains, and fixtures against water leaks. Not intended for use under pressure.

Plumbing Tree: A network of pipes and fittings that branch off from a main supply line, serving multiple fixtures in a building.

Plunger: A rubber cup with a handle used to create suction and dislodge clogs in drains and toilets.

Pneumatic: A plumbing system or component that operates using air pressure to control water flow or activate valves.

Point Of Use Water Heater: A compact water heater installed near a specific fixture, such as a sink, to provide immediate hot water without waiting for it to travel through pipes.

Pop-Up Assembly: A drain assembly that allows the user to open or close a drain stopper with a lever or knob. Common in bathroom sinks.

Pop-Up Drain: A drain with a movable stopper that can be raised or lowered using a lever. Allows water to be held in or released from a sink or tub.

Porcelain: A durable ceramic material used for plumbing fixtures like sinks, toilets, and tubs. Often coated with a glossy enamel finish.

Porcelain Enamel: A glassy coating fused to metal fixtures to create a smooth, durable surface that resists staining and corrosion.

Port: An opening or passage in a valve, fitting, or fixture that allows water or air to flow through.

Potable Water: Water that is safe for drinking and cooking, free from contaminants or pollutants.

Power Flush System: A toilet flushing system that uses pressurized air to deliver a more powerful flush than gravity-operated systems.

Pressure-Assisted Toilets: Toilets that use a pressurized tank to increase the force of the flush, reducing the likelihood of clogs.

Pressure-Balancing Valve: A valve that maintains consistent water pressure by adjusting hot and cold water flow, preventing sudden temperature changes.

Priming Jet: A small opening in a toilet bowl that directs water flow to initiate the flushing process.

Proximity Valve: A valve that is activated by motion or presence detection, often used in hands-free faucets and urinals.

P-Trap: A curved section of drainpipe designed to hold water and prevent sewer gases from entering the home. Common under sinks and showers.

Public Sewer: A municipal or government-operated wastewater system that collects and treats wastewater from multiple properties.

Pull Out Spray: A type of kitchen faucet with a detachable spray head that allows for flexible rinsing and cleaning.

Reducer: A fitting that connects pipes of different sizes, allowing for a gradual change in diameter. Prevents pressure drops in the system.

Refill Tube: A small tube that directs water from the fill valve to the overflow tube in a toilet tank, ensuring proper water level.

Relief Valve: A safety valve that opens to release excess pressure from a system, preventing damage or rupture. Common in water heaters.

Return Line: A pipe that carries cooled or used water back to a heating source or recirculation system, maintaining balanced water flow.

Riser: A vertical pipe that carries water from a lower level to a higher level, such as in a multi-story building.

Rough-In: The initial plumbing installation phase in which pipes, vents, and drains are positioned before walls and floors are finished.

Rough-In Dimensions: The specific measurements for fixture placement, including drain locations, supply lines, and vent connections.

Run: The horizontal distance between two points in a plumbing system, such as between a fixture and the main drain line.

S-Trap: A trap shaped like an ‘S’ that connects a sink drain to the sewer line. Often replaced with P-traps due to venting issues.

Saddle Valve: A valve that clamps onto a pipe to create a small water supply line, often used for ice makers or humidifiers.

Sanitary Fitting: A plumbing fitting designed with smooth surfaces and minimal corners to prevent debris buildup and promote proper drainage.

Sanitary Sewer: A drainage system that carries wastewater from sinks, toilets, and showers to a treatment plant, separate from stormwater sewers.

Sanitary Tee: A T-shaped fitting that connects horizontal and vertical drainpipes, allowing waste to flow through without obstructing the vent.

Self-Rimming Sink: A sink with a lip that rests on top of the countertop, making it easier to install and seal against leaks.

Septic Tank: A watertight chamber that collects and treats household wastewater using natural bacterial decomposition before discharging to a drain field.

Sewer: A system of underground pipes that transports wastewater from buildings to a treatment facility or septic system.

Sewerage System: A network of pipes, pumps, and treatment facilities that manage wastewater and sewage disposal for a community or city.

Shroud: A decorative cover used to conceal exposed plumbing components, such as sink traps or toilet flush valves.

Shut-Off Valve: A valve that controls water flow to a fixture or appliance, allowing it to be isolated for repairs or maintenance.

Siphon Break: A device that prevents backflow by introducing air into a pipe, breaking the siphon effect and protecting potable water.

Siphon-Vortex Water Closet: A type of toilet that uses a vortex motion to clear the bowl with minimal water usage, reducing clogs and conserving water.

Siphoning: The unintended flow of water or waste from a lower level to a higher level, caused by pressure changes or blockages in the plumbing system.

Sleeve: A protective casing that surrounds pipes passing through walls or floors, preventing damage and ensuring a clean, finished appearance.

Slip Joint: A plumbing connection that allows for slight adjustments by sliding one pipe over another and securing it with a nut and washer.

Slope: The angle or pitch of a drainpipe that ensures wastewater flows toward the sewer line without pooling or backflowing.

Soil Pipe: A pipe that carries waste from toilets or urinals to the sewer or septic system, typically vented to prevent sewer gases from entering the building.

Soil Stack: A vertical pipe that collects waste from multiple floors and directs it to the main sewer line. Also serves as a vent to prevent siphoning.

Solder: A metal alloy used to join copper pipes and fittings by melting and fusing the joint, creating a watertight seal.

Spigot: An outdoor faucet or tap used to connect garden hoses and provide water for irrigation or washing.

Stack: A main vertical drainpipe that carries waste from multiple floors to the building’s main sewer line.

Stack Vent: A vertical extension of a soil stack that allows sewer gases to escape while maintaining air pressure to prevent trap siphoning.

Stand Pipe: A vertical pipe that serves as an emergency water discharge outlet, preventing flooding in areas like basements and laundry rooms.

Static Lift: The vertical distance water must be lifted in a plumbing system, affecting pump selection and water pressure.

Static Pressure: The pressure of water in a plumbing system when no water is flowing, measured in pounds per square inch (PSI).

Stop Valve: A valve that controls water flow to a specific fixture or appliance, allowing it to be turned off for repairs or maintenance.

Storm Sewer: A separate drainage system that carries rainwater and runoff away from buildings, preventing flooding and water damage.

Straight Cross: A plumbing fitting shaped like a cross with four openings, allowing pipes to connect at 90° angles. Used to distribute water to multiple branches.

Straight Stop Valve: A shut-off valve with a straight inlet and outlet, commonly installed under sinks and toilets to control water flow.

Street Elbow: An elbow fitting with one female-threaded end and one male-threaded end, allowing pipes to change direction while connecting different fitting types.

Sump: A pit or basin designed to collect water, typically located in basements to prevent flooding. Often connected to a sump pump.

Sump Pump: A submersible or pedestal pump that removes water from a sump basin, directing it away from the building to prevent flooding.

Supply Line: A pipe that carries potable water from the main supply to fixtures and appliances, such as sinks, toilets, and water heaters.

T-Bolt: A threaded bolt with a T-shaped head used to secure toilet bowls to the floor flange. Also known as closet bolts.

Tail Pipe: A section of pipe that extends from a fixture’s drain to the main drain line, allowing wastewater to exit the fixture.

Tailpiece: A short vertical pipe that connects a sink drain to a P-trap or other drain fitting, often adjustable in length.

Tank: A reservoir that stores water for toilets, water heaters, or pressure systems. Can be pressurized or gravity-fed.

Tank Ball: A rubber ball in toilet tanks that lifts to allow water to flush and seals to refill the tank.

Tank Bolts: Bolts that secure a toilet tank to the bowl, preventing leaks and maintaining structural stability.

Tank Cover Lock: A locking mechanism that prevents unauthorized access to a toilet tank, typically used in public restrooms.

Tank Cross: A cross-shaped fitting that connects multiple pipes to a central water heater or boiler, distributing hot water to various fixtures.

Tankless Water Heater: A water heater that heats water on demand without a storage tank, providing continuous hot water and reducing standby heat loss.

Tap Tee: A fitting that allows a smaller pipe to branch off a larger main pipe at a 90° angle, often used for irrigation or appliance connections.

Tee: A T-shaped fitting that connects three pipes, allowing water to flow in multiple directions or branch off a main line.

Teflon Tape: A thin, white tape used to seal threaded pipe joints, preventing leaks and ensuring a watertight connection.

Temperature Rise: The increase in water temperature as it passes through a water heater, measured in degrees Fahrenheit or Celsius.

Thermal Expansion: The increase in water volume due to heating, which can create excess pressure in a closed plumbing system.

Thermal Shock: A sudden temperature change that can cause pipes to crack or fittings to loosen, often due to hot water entering a cold pipe.

Thermocouple: A safety device that detects the pilot light flame in gas water heaters and shuts off the gas if the flame goes out.

Thermostatic Valve: A valve that maintains a consistent water temperature by automatically adjusting the hot and cold water mix.

Thread Sealant: A paste or tape applied to threaded pipe connections to prevent leaks and ensure a tight seal.

Through-the-Floor: A plumbing installation method where pipes run through the floor rather than through walls, common for toilets and floor drains.

Thumb Nut: A nut that can be tightened or loosened by hand without tools, commonly used in sink drain assemblies.

Thumb Screw: A screw with a ridged head that can be turned by hand, often used for securing small plumbing components.

Tile-In: A sink or fixture that is mounted flush with surrounding tile, creating a seamless and integrated appearance.

Toilet Setting Compound: A putty or sealant applied to the base of a toilet to prevent leaks and provide a secure seal against the floor.

Torque Wrench: A specialized wrench that applies a specific amount of force to bolts and nuts, ensuring proper tightening without over-tightening.

Transfer Valve: A valve that diverts water from one outlet to another, such as from a tub spout to a showerhead.

Trap: A curved section of drainpipe designed to hold water and prevent sewer gases from entering the building. Common types include P-traps and S-traps.

Trap Arm: The horizontal section of pipe that connects a trap to the main drainage system, maintaining proper slope to prevent clogs.

Trap Dip: The lowest point in a plumbing trap where water collects to prevent sewer gas from escaping.

Trap Seal: The standing water in a trap that acts as a barrier against sewer gases, maintaining the integrity of the plumbing system.

Trapway: The internal passage in a toilet bowl that carries waste to the drain. Wider trapways reduce the risk of clogs.

Trip Arm: A lever or handle in a toilet tank that raises and lowers the flapper, initiating the flushing cycle.

Trip Chain: A chain that connects the toilet handle to the flapper, allowing the handle to lift the flapper during flushing.

Trip Lever: A handle or lever that activates the flushing mechanism in a toilet, usually located on the side of the tank.

Tube: A cylindrical conduit for transporting water, gas, or waste. Smaller in diameter than pipes and often made of copper, PEX, or PVC.

Turbulent Flow: A type of water flow characterized by rapid changes in pressure and velocity, increasing friction and reducing system efficiency.

Two-Piece Toilet: A toilet design in which the tank and bowl are separate components bolted together during installation, making them easier to transport and repair.

Uni-flex: A flexible water supply connector used to connect faucets, toilets, or water heaters to the main supply line. Often made of braided stainless steel or reinforced PVC.

Union: A three-part fitting that allows two pipes to be easily disconnected and reconnected without cutting the pipes. Useful for maintenance or repairs.

Usable Storage: The actual volume of water available for use in a storage tank or water heater, excluding the space occupied by air or insulation.

Vacuum Breaker: A backflow prevention device that introduces air into a system to prevent siphoning and contamination of potable water.

Vacuum Relief Valve: A valve that opens to admit air into a plumbing system when a vacuum is detected, preventing pipe collapse or backflow.

Valve: A device that controls the flow of water, gas, or other fluids through a pipe or system. Types include ball valves, gate valves, and check valves.

Valve Seat: The surface inside a valve where the moving part (e.g., washer, disc) seals against to stop the flow of water.

Vanity: A cabinet that supports a bathroom sink and conceals plumbing pipes, providing storage space beneath the sink.

Vent: A pipe that allows air to enter the drainage system, preventing trap siphoning and ensuring proper drainage flow.

Vent Header: A horizontal pipe that connects multiple vent pipes, allowing air to circulate and preventing pressure imbalances in the system.

Vent Stack: A vertical pipe that extends above a building’s roofline to release sewer gases and maintain proper air pressure in the drainage system.

Vent System: A network of pipes that regulate air pressure in a plumbing system, preventing trap siphoning and allowing gases to escape.

Venturi: A device that uses a constricted section of pipe to increase fluid velocity and decrease pressure, commonly used in pumps and water systems.

Viscosity: A measure of a fluid’s resistance to flow. Higher viscosity fluids (e.g., grease) move more slowly than lower viscosity fluids (e.g., water).

Vitreous: A glassy, non-porous coating applied to plumbing fixtures like sinks and toilets to provide a smooth, durable surface.

Vitreous China: A type of ceramic material coated with a glossy, glass-like finish, making it durable, stain-resistant, and easy to clean.

Washdown Water Closet: A type of toilet bowl design that uses direct water flow to push waste down the drain, reducing the risk of clogs.

Waste Arm: A horizontal pipe that carries wastewater from a fixture to the main drain line, typically located under sinks or tubs.

Waste & Overflow: A combined drain assembly for bathtubs that allows water to exit through the main drain or overflow outlet, preventing spills.

Water Consumption: The amount of water used by a plumbing fixture, appliance, or system, typically measured in gallons per minute (GPM).

Water Hammer: A loud banging noise caused by the sudden stopping of water flow, resulting in pressure surges and potential pipe damage.

Water Hardness: A measure of dissolved minerals in water, primarily calcium and magnesium. High hardness can cause scale buildup in pipes and fixtures.

Water Main: A large underground pipe that distributes potable water from the municipal supply to individual buildings and properties.

Water Service Pipe: A pipe that connects a building’s plumbing system to the public water main, delivering potable water.

Water Softener: A device that removes calcium and magnesium ions from hard water, preventing scale buildup and extending the life of plumbing fixtures.

Water Supply Line: A pipe that delivers potable water to plumbing fixtures and appliances, such as sinks, toilets, and washing machines.

Waterway Fitting: A fitting designed to direct water flow efficiently through a plumbing system, minimizing friction loss and optimizing pressure.

Wet Vent: A vent pipe that also carries wastewater from a fixture, combining the functions of a drain and a vent in one pipe.

Widespread: A faucet style with separate hot and cold handles mounted apart from the spout, allowing for custom spacing.

Working Pressure: The maximum pressure a plumbing system or fixture can safely handle during normal operation, measured in pounds per square inch (PSI).

Wye/WYE: A Y-shaped fitting that connects three pipes at a 45° angle, directing flow while reducing friction and turbulence.

Yoke: A plumbing fitting that stabilizes two connected pipes, preventing movement and reducing the risk of leaks.

Yoke Vent: A vent that connects a soil stack to a vent stack to balance air pressure and prevent trap siphoning.

Plumbing Slang Terms You’ll Hear on the Jobsite

Slang is part of jobsite culture. It’s how experienced plumbers pass down knowledge, share a laugh, or describe a process in a way that everyone understands. 

Learning plumbing slang terms doesn’t just help you fit in; it also helps you work smarter and communicate more clearly.

Here’s a quick guide to some common slang you’ll hear in the plumbing world, organized alphabetically:

Plumbing Acronyms and Abbreviations

Commonly seen in blueprints, specs, and invoices, plumbing acronyms and plumbing abbreviations help plumbers communicate quickly and effectively on the jobsite. 

Here’s a comprehensive list of the most common plumbing acronyms and their plain-English definitions:

A/E (Architect/Engineer): A professional responsible for designing and overseeing construction projects, including plumbing systems.

AAV (Air Admittance Valve): See ‘Air Admittance Valve’ under “Essential Plumbing Terms and Definitions”.

ABS (Aristocraft Bristone Styrine): A durable, black plastic piping material used for drain, waste, and vent lines.

AD (Area Drain/Access Door): A floor drain that collects surface water or an access panel that provides entry to plumbing components for inspection or maintenance.

ADA (Americans with Disability Act): U.S. legislation requiring accessibility features in plumbing fixtures, such as sinks and toilets, for individuals with disabilities.

AFF (Above Finish Floor): The height of a fixture, pipe, or fitting measured from the finished floor level.

AFG (Above Finish Grade): The height of a plumbing component measured from the finished ground level.

AG (Air Gap): See ‘Air Gap’ under “Essential Plumbing Terms and Definitions”. 

AGA (American Gas Association): A trade organization that establishes safety standards and guidelines for natural gas appliances and plumbing systems.

AP (Access Panel): See ‘Access Panel’ under “Essential Plumbing Terms and Definitions”. 

AS (Automatic Sprinkler): A fire suppression system that automatically releases water when triggered by heat or smoke.

ASD (Adjustable Speed Drives/Automatic Sprinkler Drain): Electrical devices that control the speed of pumps or motors, or a drainage system for automatic sprinklers.

ASHRAE (American Society of Heating, Refrigeration, Air Conditioning Engineers): An international society that sets standards for heating, cooling, and plumbing system design and performance.

ASME (American Society of Mechanical Engineers): A professional association that develops standards and codes for mechanical and plumbing systems.

ASPE (American Society of Plumbing Engineers): A professional organization that provides technical resources and training for plumbing engineers.

ASR (Automatic Sprinkler Riser): A vertical pipe that supplies water to a sprinkler system, distributing it to various sprinkler heads.

AV (Acid Vent): A vent pipe that handles acidic waste gases from chemical or laboratory drains.

AW (Acid Waste): Wastewater that contains acidic substances, typically found in laboratory or industrial plumbing systems.

BC (Brushed Chrome – Finish): A type of faucet or fixture finish that has a matte, polished silver appearance.

BFP (Backflow Preventer): See ‘Backflow Preventer’ under “Essential Plumbing Terms and Definitions”.

BHP (Break Horsepower): The power output of a pump or motor before losses caused by friction and other factors, measured in horsepower.

BN (Brushed Nickel – Finish): A finish applied to faucets, fixtures, and hardware with a soft, satin-like appearance, often used in bathrooms and kitchens.

BSP (Black Steel Pipe): A type of uncoated steel pipe commonly used for gas lines, fire sprinkler systems, and industrial applications.

BT (Bathtub): A plumbing fixture designed for bathing, available in various materials such as acrylic, cast iron, and fiberglass.

BTU (British Thermal Unit): A measurement of heat energy; one BTU raises the temperature of one pound of water by one degree Fahrenheit.

BTUH (British Thermal Unit Per Hour): A unit of heat output used to measure the heating capacity of appliances like water heaters and boilers.

C (Celsius): A temperature scale in which water freezes at 0°C and boils at 100°C under standard atmospheric pressure.

CA (Compressed Air): Air that is pressurized for use in tools, equipment, or pneumatic systems in plumbing and industrial applications.

CGA (Compressed Gas Association): A trade association that develops safety standards and guidelines for the storage and handling of compressed gases.

CFM (Cubic Feet Per Minute): A measurement of airflow, indicating how much air passes through a given point per minute; used in ventilation and HVAC systems.

CI (Cast Iron): A durable, heavy-duty metal used for plumbing pipes, especially in drainage and waste systems.

CO (Cleanout): See ‘Cleanout’ under “Essential Plumbing Terms and Definitions”.

CP (Polished Chrome – Finish): A shiny, reflective finish applied to faucets, fixtures, and hardware, providing a sleek, modern look.

CPVC (Chlorinated Polyvinyl Chloride): A thermoplastic material used for hot and cold water supply lines, known for its resistance to heat and chemicals.

CS (Clinical Sink): A sink designed for medical or laboratory use, typically equipped with a high back and specific drainage features.

CV (Control Valve): A valve used to regulate the flow of water, gas, or other fluids in a plumbing or mechanical system.

CW (Cold Water): Potable water supplied through the plumbing system that is not heated.

CWT (Copper Water Tube): A copper pipe used for water distribution, available in various thicknesses (Types K, L, M).

DCW (Domestic Cold Water): The supply of potable cold water distributed throughout a building’s plumbing system.

DEMO (Demolition): The process of removing plumbing fixtures, pipes, or walls during a renovation or construction project.

DFU (Drainage Fixture Unit): A measure of the probable discharge from a plumbing fixture or group of fixtures, used to size drainage systems.

DHW (Domestic Hot Water): Hot water supplied for residential or commercial use, such as for showers, sinks, and appliances.

DHWR (Domestic Hot Water Return): The return line that circulates hot water back to the heater to maintain consistent temperatures in a recirculating system.

DHWS (Domestic Hot Water Supply): The supply line that delivers heated water to fixtures and appliances.

DI (Deionized Water): Water that has had most of its mineral ions removed, making it highly purified for laboratory or industrial use.

DN (Down): A directional indicator for pipes or fittings that slope downward.

DOE (Department of Energy): A U.S. government agency that establishes efficiency standards for plumbing and mechanical systems.

DS (Downspout): A vertical pipe that carries rainwater from a roof gutter to the ground or storm drain.

DW (Dishwasher): An appliance used to wash dishes, typically connected to both hot and cold water supplies.

DWG (Drawing): A technical or architectural diagram that shows the layout and specifications of a plumbing or mechanical system.

DWH (Domestic Water Heater): A unit that heats water for household use, such as showers, sinks, and washing machines.

DWR (Drinking Water Return): The return line in a plumbing system that circulates cooled drinking water back to the supply source.

DWS (Drinking Water Supply): The supply of potable water specifically intended for drinking, cooking, and food preparation.

DWV (Drain Waste Vent): A plumbing system that carries wastewater and air from fixtures to the sewer while preventing sewer gases from entering the building.

ECO (Energy Cut Off): A safety feature in water heaters that shuts off the heating element or burner when the water temperature exceeds a preset limit.

EF (Energy Factor): A measurement of a water heater’s overall efficiency based on the amount of hot water produced per unit of fuel consumed.

EL (Elevation): The vertical height of a plumbing component or fixture, usually measured from a fixed reference point such as the ground or floor.

EMCS (Energy Montserrat and Central System): A control system that monitors and manages energy usage, including heating, cooling, and plumbing systems in large buildings.

EPA (Environmental Protection Agency): A U.S. government agency that regulates environmental standards, including water quality and plumbing fixture efficiency.

EPACT (Energy Policy Act): U.S. legislation that sets minimum efficiency standards for plumbing fixtures, appliances, and heating systems.

ESC (Escutcheon): See ‘Escutcheon’ under “Essential Plumbing Terms and Definitions”.

ESH (Emergency Shower): A safety fixture designed to rinse hazardous substances from the body quickly, typically installed in industrial or lab settings.

ET (Expansion Tank): A tank that absorbs excess water pressure caused by thermal expansion in a closed plumbing system, preventing damage to pipes and fixtures.

EWH (Electric Water Heater): A water heater that uses electric heating elements to heat water, commonly installed in residential and commercial settings.

EWS (Eye Wash Station): A safety fixture that flushes chemicals or debris from the eyes, typically found in industrial or laboratory settings.

EWS/SH (Eye Wash/Drench Shower): A combined fixture that provides both eye washing and full-body rinsing for chemical exposure emergencies.

ETR (Existing to Remain): A notation in construction plans indicating that a plumbing component or fixture will not be altered or removed during renovation.

F (Fahrenheit): A temperature scale in which water freezes at 32°F and boils at 212°F under standard atmospheric pressure.

FCO (Floor Clean-out): An access point installed in the floor to provide easy access for clearing clogs and inspecting drain lines.

FCW (Filtered Cold Water): Cold water that has been passed through a filtration system to remove impurities and contaminants.

FD (Floor Drain): A drain installed in the floor to remove wastewater or spills, commonly found in basements, garages, and commercial kitchens.

FDC (Fire Department Connection): A connection point for firefighters to pump water into a building’s sprinkler or standpipe system.

FHT (Female Hose Threads): A threaded fitting designed to connect with standard garden hose threads; typically used for exterior hose bibbs and faucets.

FIP (Female Iron Pipe – Threaded): A pipe fitting with internal threads that connects to a male-threaded fitting to create a secure joint.

FM (Flow Meter): A device used to measure the flow rate of water, gas, or other fluids in a plumbing system, usually expressed in gallons per minute (GPM).

FNPT (Female National Pipe Thread): A standard thread used on female fittings to connect to male NPT threads, ensuring a secure, leak-proof joint.

FOP (Fuel Oil Pump): A pump that circulates fuel oil from a storage tank to a burner or other appliance.

FOR (Fuel Oil Return): A line that returns unused fuel oil back to the storage tank, maintaining consistent pressure in the system.

FOS (Fuel Oil Supply): The supply line that delivers fuel oil from the storage tank to the burner or appliance.

FOV (Fuel Oil Vent): A vent line that releases excess pressure or vapors from a fuel oil tank to prevent overpressurization.

FS (Floor Sink/Flow Switch): A drainage fixture installed in floors to receive wastewater from indirect waste lines or a flow switch that activates when a specific flow rate is detected.

FSWT (Female Sweat Connection): A fitting that is soldered (sweated) to a copper pipe, creating a leak-proof joint.

FU (Fixture Units): A unit of measure that quantifies the demand placed on a plumbing system by fixtures, such as sinks, toilets, and showers.

GAL (Gallon): A unit of liquid measurement equal to 128 ounces or 3.785 liters, commonly used to measure water volume in plumbing systems.

GCO (Grade Cleanouts): Access points located at ground level that provide access to drainage pipes for clearing clogs and inspecting lines.

GPD (Gallons Per Day): The total volume of water used or processed by a fixture or system in a 24-hour period.

GPF (Gallons Per Flush): The amount of water used by a toilet per flush cycle. Modern toilets typically use 1.6 GPF or less to conserve water.

GPH (Gallons Per Hour): The flow rate of water expressed as the number of gallons passing through a system in one hour.

GPM (Gallons Per Minute): A common flow rate measurement for plumbing fixtures, indicating how many gallons of water pass through a fixture or pipe per minute.

GPR (Gas Pressure Regulator): A device that maintains a constant gas pressure to appliances, preventing pressure spikes and ensuring safe operation.

GRS (Gas Regulator Station): A control point in a gas distribution system where pressure is regulated and monitored before entering the building.

GT (Grease Trap): A plumbing device installed to capture grease, oils, and solids before they enter the main drainage system, preventing clogs and backups.

GVTR (Gas Vent Through Roof): A pipe that vents gases from appliances like water heaters and furnaces to the outside through the roof.

GWH (Gas Fired Water Heater): A water heater that uses natural gas or propane as the fuel source to heat water for residential or commercial use.

H&CW (Hot & Cold Water): The supply of both hot and cold potable water delivered to fixtures and appliances throughout a building.

HB (Hose Bibb): See ‘Hose Bibb’ under “Essential Plumbing Terms and Definitions”.

HD (Hub Drain): A floor drain with a raised inlet, allowing indirect waste connections from sinks, appliances, or equipment.

HET (High Efficiency Toilet): A toilet designed to use 1.28 gallons per flush or less, reducing water consumption compared to standard models.

HEU (High Efficiency Urinal): A urinal that uses 0.5 gallons per flush or less, minimizing water use in commercial and industrial settings.

HEX (Heat Exchanger): A device that transfers heat from one fluid or gas to another without mixing them, commonly used in water heaters and boilers.

HP (Horsepower): A unit of measurement that indicates the power output of pumps, motors, and other mechanical equipment.

HS (Hand Sink): A small sink typically used for handwashing, often found in kitchens, bathrooms, and commercial settings.

HST (Hot Water Storage Tank – Domestic): A tank that stores heated water for domestic use, ensuring a consistent supply of hot water to fixtures.

HWB (Hot Water Boiler): A boiler that heats water and distributes it through pipes for space heating or domestic hot water use.

HWCP (Hot Water Circulating Pump): A pump that circulates hot water throughout a plumbing system to reduce wait times for hot water at fixtures.

HWP (Hot Water Pump): A pump used to circulate hot water through a heating system or plumbing network.

HWT (Hot Water Tank): A storage tank that holds heated water for use in fixtures and appliances, often insulated to retain heat.

HYD (Hydrant): A valve-equipped outlet connected to a water main, providing water for fire suppression or outdoor use.

ID (Inside Diameter): The internal width of a pipe or fitting, important for calculating flow rates and ensuring proper pipe sizing.

IE (Invert Elevation): The lowest point or bottom elevation of a drain or sewer pipe, used to determine the slope for proper drainage.

ICW (Industrial Cold Water): Cold water supplied for industrial use, often requiring specific treatment or conditioning based on the application.

IHW (Industrial Hot Water): Hot water supplied for industrial processes, typically generated by boilers or industrial water heaters.

INV (Invert): The lowest interior surface of a drainpipe, where wastewater flows; critical for maintaining proper flow and slope.

IPC (International Plumbing Code): A set of plumbing regulations that provide guidelines for the design, installation, and inspection of plumbing systems.

IPS (Iron Pipe Size): A sizing standard used for pipes and fittings, commonly referenced in plumbing specifications and product labels.

IRW (Irrigation Water): Water supplied specifically for landscape or agricultural irrigation systems, often untreated or recycled.

IW (Indirect Waste): Wastewater that discharges to the drainage system through an air gap to prevent backflow contamination.

IWH (Instantaneous Water Heater): A water heater that heats water only when needed, without storing it, reducing energy consumption.

IWR (Industrial Water Return): The return line for industrial water systems, directing unused or cooled water back to its source or treatment system.

IWS (Industrial Water Supply): The main water supply for industrial facilities, often requiring treatment or filtration based on the intended use.

KW (Kilowatt): A unit of power equal to 1,000 watts, used to measure the output of heating systems, pumps, and other electrical equipment.

KWH (Kilowatt Hour): A unit of energy representing the consumption of one kilowatt of power for one hour, commonly used to measure electricity usage.

L/S (Liter Per Second): A flow rate measurement indicating the volume of water or fluid passing through a pipe per second, often used in drainage calculations.

LA (Laboratory Air): Compressed air supplied to laboratory workstations for testing, cleaning, or operating pneumatic equipment.

LAV (Lavatory): See ‘Lavatory’ under “Essential Plumbing Terms and Definitions”.

LBS/HR (Pounds Per Hour): A flow rate measurement indicating the weight of a substance moving through a system per hour, often used for steam or water.

LCW (Laboratory Cold Water): Cold water supplied to laboratory fixtures, often treated or filtered to meet specific testing or research standards.

LHW (Laboratory Hot Water): Hot water supplied to laboratory sinks or workstations, typically regulated to prevent scalding.

LNG (Liquid Natural Gas): Natural gas that has been cooled to a liquid state for storage or transportation, used as a fuel source in some heating systems.

LOX (Liquid Oxygen): Oxygen in liquid form, stored at extremely low temperatures, often used in medical or industrial applications.

LV (Laboratory Vacuum): A vacuum system installed in laboratory settings to provide suction for experiments or equipment operation.

LW (Low Water): A designation for water levels that have dropped below a specified point, potentially affecting system pressure or operation.

LWCO (Low Water Cut Off): A safety device that shuts off a boiler or water heater if the water level drops too low, preventing overheating and damage.

M (Meter): A unit of length in the metric system, equal to 3.281 feet, used in measuring pipe lengths and fixture heights.

MA (Medical Air): Clean, dry air used in medical facilities for patient care and laboratory work, typically supplied through a central system.

MAV (Manual Air Vent): A valve that releases trapped air from plumbing or heating systems to maintain proper flow and pressure.

MBH (1000 BTUH): A measurement of heating output; 1 MBH equals 1,000 BTUs per hour.

MED (Medical): Related to plumbing systems in healthcare settings, such as medical gas lines or emergency showers.

MER (Mechanical Equipment Room): A dedicated space for housing plumbing, HVAC, and other mechanical equipment in a building.

MH (Manhole): A covered opening that provides access to underground pipes, sewers, or utility lines for inspection and maintenance.

MHT (Male Hose Threads): A threaded fitting designed to connect to female hose threads, commonly used on outdoor faucets and hose bibbs.

MIP (Male Iron Pipe – Threaded): A pipe or fitting with external threads that screw into a female-threaded fitting to form a connection.

MOU (Memorandum of Understanding): An agreement or contract outlining the scope of work, specifications, or responsibilities in a plumbing project.

MSB (MOP Service Basin): A floor-mounted basin used for cleaning equipment or disposing of mop water in commercial settings.

MV (Medical Vacuum): A suction system used in medical facilities for patient care, often connected to central piping.

N2 (Nitrogen): An inert gas commonly used in HVAC and plumbing systems for pressure testing and leak detection.

N2O (Nitrous Oxide): A gas used in medical facilities for anesthesia, supplied through a central medical gas system.

NC (Normally Closed): A valve or switch that remains closed when not in use, allowing flow only when activated.

NG (Natural Gas): A flammable gas used as a fuel source for water heaters, boilers, and heating systems.

NIC (Not In Contract): A notation indicating that specific work is not included in the contract scope, requiring separate arrangements.

NO (Normally Open): A valve or switch that remains open when not in use, allowing flow until activated to close.

NOM. (Nominal): The approximate size of a pipe or fitting, often differing slightly from the actual measurements.

NPT (National Pipe Tapered Thread): A standardized thread used for sealing connections in plumbing pipes and fittings.

NPW (Non Potable Water): Water not suitable for drinking, often used for irrigation, fire suppression, or industrial applications.

NTS (Not To Scale): A designation for drawings or diagrams that are not drawn to precise scale but illustrate general design intent.

O2 (Oxygen): A medical gas supplied through a central system in hospitals or clinics for patient care.

OC (On Center): The distance from the center of one pipe, stud, or fixture to the center of the next, used for layout measurements.

OD (Outside Diameter): The external measurement of a pipe, used to determine pipe size and fitting compatibility.

OFD (Overflow Drain): A secondary drain installed to prevent flooding by redirecting excess water away from a fixture or appliance.

OVFL (Overflow): The condition where water exceeds the intended level in a fixture or tank, leading to spillage.

PA (Pascal): A unit of pressure measurement equal to one newton per square meter, commonly used in plumbing and HVAC systems.

PD (Pressure Drop/Difference): The reduction in pressure as water or gas flows through pipes, fittings, or fixtures.

PDI (Plumbing and Drainage Institute): A trade organization that sets standards for backflow preventers, grease interceptors, and other plumbing components.

PEX (Crosslinked Polyethylene): A flexible, durable plastic piping material used for water distribution in residential and commercial plumbing.

PG (Pressure Gage): A device that measures water or gas pressure in a plumbing system, typically expressed in PSI.

PP (Plumbing Pump): A mechanical device that moves water or other fluids through a plumbing system to maintain pressure and flow.

PPM (Parts Per Million): A unit of measurement that indicates the concentration of substances in water, such as minerals or contaminants.

PRS (Pressure Reducing Station): A control point in a plumbing system where pressure is regulated to prevent damage to pipes and fixtures.

PRV (Pressure Reducing Valve): A valve that reduces incoming water pressure to a safer, more manageable level for plumbing fixtures.

PSI (Pounds Per Square Inch): A unit of pressure measurement used to gauge water, gas, or air pressure in plumbing systems.

PSIA (Pounds Per Square Inch Atmosphere): Absolute pressure measurement that includes atmospheric pressure in the reading.

PSIG (Pounds Per Square Inch Gage): Gauge pressure measurement that does not include atmospheric pressure, only the pressure within the system.

PTRV (Pressure Temperature Relief Valve): A safety valve that releases water to prevent overpressure or overheating in water heaters.

PVC (Polyvinyl Chloride): A durable plastic piping material used for drain, waste, and vent (DWV) systems and cold water supply lines.

PW (Potable Water): Water that is safe for drinking, cooking, and other domestic uses, treated to meet health standards.

RD (Roof Drain): A drain installed on flat roofs to channel rainwater to the stormwater system or ground level.

RDL (Roof Drain Leader): The vertical pipe that directs water from a roof drain to a lower-level drainage system.

RL (Roof Leader): A pipe that carries stormwater runoff from the roof to a ground-level drain or storm sewer.

RP (Recirculation Pump): A pump that circulates hot water through a plumbing system to reduce wait times at fixtures.

RO (Reverse Osmosis Water): Purified water that has been filtered through a membrane to remove contaminants and dissolved solids.

RWL (Rain Water Leader): A pipe that conveys rainwater from the roof to a drainage system or ground level.

SAN (Sanitary Sewer): See ‘Sanitary Sewer’ under “Essential Plumbing Terms and Definitions”.

SMACNA (Sheet Metal and Air Conditioning Contractors National Association): An organization that sets guidelines for HVAC and ductwork systems, including plumbing vents.

SCFM (Standard Cubic Foot/Minute): A flow rate measurement that accounts for air or gas volume under standard pressure and temperature conditions.

SCH (Schedule – Pipe Wall Thickness): A rating system that indicates the wall thickness of pipes, with higher numbers representing thicker walls.

SCW (Softened Cold Water): Cold water that has been treated with a water softener to remove minerals like calcium and magnesium.

SDMH (Storm Drain Manhole): A manhole providing access to stormwater drainage systems for inspection and cleaning.

SMH (Sanitary Manhole): A manhole that provides access to sanitary sewer systems for maintenance and inspection.

SP (Sump Pump): A pump installed in a pit or basin to remove accumulated water and prevent flooding in basements or crawl spaces.

SPR (Sprinkler Line): A plumbing line dedicated to fire sprinkler systems, distributing water to sprinkler heads in case of fire.

SQFT/S (Square Feet per Second): A flow rate measurement indicating how much area water covers per second, used in stormwater management.

SS (Stainless Steel): A corrosion-resistant metal commonly used for pipes, fittings, and fixtures in plumbing systems.

ST (Storage Tank): A tank used to store water for domestic, industrial, or fire protection purposes.

SW (Storm Water): Rainwater or runoff that is collected and conveyed away from roofs, streets, and parking lots.

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T&P Valve (Temperature and Pressure Relief Valve): A safety valve installed on water heaters to release excess pressure or temperature to prevent tank rupture.

TCV (Temperature Control Valve): A valve that regulates water temperature by mixing hot and cold water to maintain a consistent output.

TD (Temperature Difference/Trench Drain): The variance in temperature between two points in a plumbing system, or a channel drain designed to collect surface water.

TDH (Total Dynamic Head): The total pressure a pump must overcome to move water through a plumbing system, factoring in friction loss, elevation, and flow rate.

TEMP (Temperature): The measure of how hot or cold water or air is within a plumbing system, typically expressed in Fahrenheit or Celsius.

TMV (Thermostatic Mixing Valve): A valve that automatically mixes hot and cold water to prevent scalding and maintain a safe, consistent temperature.

TP (Trap Primer): A device that maintains the water seal in a plumbing trap by adding water periodically to prevent sewer gases from escaping.

TPI (Threads Per Inch): A measurement indicating the number of threads on a pipe fitting per inch, determining compatibility and tightness of connections.

TSTAT (Thermostat): A temperature-sensitive device that controls heating or cooling equipment by signaling when to turn on or off.

TWR (Tempered Water Return): The return line that circulates tempered water back to its source in a hot water recirculation system.

TWS (Tempered Water Supply): The supply line that delivers water maintained at a specific, safe temperature, often regulated by a TMV.

TYP (Typical): A notation in drawings or specifications indicating that a condition or component is standard throughout the project.

UNC (Unified National Coarse Thread): A standardized thread type with a larger pitch than UNF, used for general-purpose plumbing and mechanical fittings.

V (Vent): See ‘Vent’ under “Essential Plumbing Terms and Definitions”.

VAC (Vacuum): A negative pressure condition created in a plumbing system to facilitate the movement of fluids or prevent backflow.

VB (Vacuum Breaker): See ‘Vacuum Breaker’ under “Essential Plumbing Terms and Definitions”.

VCO (Vacuum Cleaner Outlet): A dedicated outlet for connecting a central vacuum system, commonly found in commercial or industrial settings.

VP (Vacuum Pump): A mechanical device that removes air or gas to create a vacuum, often used in HVAC or plumbing systems.

VS (Vent Stack): A vertical pipe that allows air to enter and escape the drainage system, preventing pressure imbalances and siphoning.

VSD (Variable Speed Drive): A motor controller that adjusts the speed and torque of pumps or fans to optimize flow rates and reduce energy consumption.

VTR (Vent Through Roof): A vertical vent pipe that terminates above the roofline to release sewer gases and maintain system pressure.

W (Waste): Wastewater from sinks, showers, and appliances that is carried through a drainage system to a sanitary sewer or septic tank.

WC (Water Closet): Another term for a toilet, referring to the fixture that disposes of human waste.

WCO (Wall Cleanout): An access point in a plumbing wall that provides access to drain lines for maintenance and clearing blockages.

WG (Water Gage): A device that measures the pressure of water within a plumbing system, typically expressed in PSI.

WH (Wall Hydrant/Water Heater): A wall-mounted outdoor faucet or a device that heats water for domestic or industrial use.

WHA (Water Hammer Arrester): A device that absorbs the shock of sudden water pressure changes to prevent noisy pipe banging and potential damage.

WL (Water Line): A pipe that conveys water from the main supply to fixtures and appliances within a building.

WM (Water Meter): A device that measures the volume of water flowing through a plumbing system, typically used for billing purposes.

WOG (Water, Oil, Gas – Pressure Rating): A rating that indicates a fitting or valve is suitable for use with water, oil, and gas under specified pressure limits.

WPD (Water Pressure Drop): The reduction in pressure that occurs as water flows through pipes, fittings, or fixtures in a plumbing system.

WS (Waste Stack): A vertical pipe that carries wastewater from multiple fixtures to the building’s main drain line.

WSFU (Water Supply Fixture Units): A unit of measurement used to calculate the demand on a water supply system based on the number and type of plumbing fixtures.

YCO (Yard Cleanup): An exterior cleanout located in a yard or outside area, providing access to drain lines for maintenance.

YH (Yard Hydrant): An outdoor water supply outlet, typically equipped with a frost-proof valve to prevent freezing in cold weather.

How to Learn and Use Plumbing Terms Confidently

Here are some practical ways to get familiar with plumbing terms and definitions and use them effectively:

• Read Job Specs and Blueprints: Review plans and specifications regularly to see how terms like ‘rough-in,’ ‘trap arm,’ and ‘pressure-balancing valve’ are used in context.
• Ask Experienced Plumbers: Don’t be afraid to ask seasoned pros to explain unfamiliar terms or slang. You’ll not only learn what they mean but also how they’re used on the job.
• Join Online Forums and Groups: Platforms like r/Plumbing on Reddit or specialized Facebook groups are great for asking questions and getting real-world examples of plumbing terms in action.
• Keep a Glossary Handy: Create your own glossary of commonly used terms, including slang, abbreviations, and code references. Add to it as you learn new words.
• Use Flashcards or Quiz Apps: Turn terms and definitions into flashcards for quick study sessions. Apps like Quizlet let you create custom sets for plumbing terminology.
• Review Codebooks and Manuals: Plumbing codes and manufacturer manuals are filled with technical terms. Reading them helps you understand how terms are used in specifications and regulations.
• Practice Explaining Terms: Whether you’re training a new apprentice or talking to a client, practice explaining terms in simple, everyday language. The more you explain, the more natural it will feel.

Final Thoughts

Whether you’re roughing in a new build, installing a grease trap, or troubleshooting a sump pump, knowing the language of the trade keeps you a step ahead.

But understanding the lingo is just the start. Managing jobs, tracking hours, and staying on top of invoices are where the real work happens.

That’s where Workyard’s plumbing software stands apart. It digitizes your business operations so your team can book more plumbing jobs while eliminating the hassles of paperwork. 

Try Workyard free for 14 days