Plain definitions of 34 terms we use on the job in Maple Valley.
Term Index
Open any term below for a dedicated definition page.
An Air Gap is a physical separation between a water outlet and the receiving vessel or drain. The open space prevents contaminated water from flowing backward into the clean water supply. Plumbing systems use air gaps in places where backflow could create a health risk or affect the quality of drinking water.
Also called: Air Gap Fitting
An Angle Stop is a small shutoff valve that controls water flow from a supply pipe to a fixture. It usually sits where the pipe leaves the wall and turns toward a toilet, sink, or other fixture. Closing the valve stops water at that fixture without shutting off the whole building.
Also called: Angle Stop Valve, Compression Stop
An anode rod is a metal component inside many tank water heaters that helps protect the steel tank from corrosion. The rod gradually wears away as it reacts with water and minerals. Replacing a worn rod can help preserve the tank, but the correct type depends on the heater design.
Also called: Sacrificial Anode
A Backwater Valve is a plumbing device that helps stop wastewater from flowing backward through a building's sewer line. It uses a hinged flap or gate that closes when outside sewer water pushes toward the building. The valve normally stays open so wastewater can leave, but it blocks reverse flow during a sewer backup.
Also called: Sewer Backflow Valve
Compression Fitting is a removable plumbing connector that joins pipes or tubing without soldering, glue, or threaded assembly. The fitting uses a compression nut and ring to press tightly against the pipe. This seal works well for accessible water line connections and allows future removal when a repair or replacement is needed.
Also called: Compression Coupling
A dielectric union is a plumbing connector that joins dissimilar metals while limiting electrical current between them. The fitting has insulating material between its connection points. This design helps reduce galvanic corrosion where copper tubing connects to steel parts, such as a water heater tank or threaded steel pipe.
Also called: Dielectric Fitting
A Drain Auger is a plumbing tool with a flexible cable that clears blockages inside drain pipes. The cable moves through the pipe and breaks apart or pulls back material that stops water flow. A drain auger works well for localized clogs in sinks, tubs, showers, and some branch drain lines.
Also called: Drain Snake, Plumbing Snake
A Drain Flange is a fitting that connects a sink opening to a drain or garbage disposal. The flange sits at the sink basin and uses a seal to limit leaks around the opening. In a disposal installation, the flange also provides the mounting point that holds the disposal beneath the sink.
Also called: Sink Drain Flange
An expansion tank is a small pressure-control vessel connected to a closed hot-water system. It gives heated water room to expand, which helps limit pressure changes inside the piping. Water heater installations often use expansion tanks when a check valve, backflow device, or pressure-reducing valve prevents expanded water from moving back into the supply.
Also called: Thermal Expansion Tank
A Fill Valve is a toilet tank component that opens to let fresh water enter after a flush. The valve closes when the tank reaches its set water level. A working fill valve helps the toilet refill quietly and prevents water from running continuously into the bowl.
Also called: Toilet Fill Valve
A flapper is a rubber or plastic seal inside a toilet tank that covers the flush valve opening. Pressing the toilet handle lifts the flapper and lets tank water enter the bowl. After the flush, the flapper should settle back onto the opening and stop water from flowing.
Also called: Flush Valve Flapper, Toilet Flapper
A Garbage Disposal Baffle is a flexible rubber guard fitted at the sink opening of a garbage disposal. The baffle helps keep food and water inside the grinding chamber while limiting access to moving parts. Its central opening lets scraps pass through when water and disposal action pull them downward.
Also called: Splash Guard
Hydrostatic Test is a plumbing pressure test that uses water to check a closed pipe system for leaks. A technician fills the system, removes trapped air, and observes whether the water pressure stays steady. For sewer line repair, the test can help confirm that repaired pipe sections hold water without leaking.
Also called: Plumbing Pressure Test
Lateral Sewer is a private underground pipe that carries wastewater from a building's plumbing to a public sewer main or shared connection. The pipe usually runs beneath the property and connects to the larger sewer network. A lateral sewer may include the section from the home to the property line or street.
Also called: Sewer Lateral
A P-Trap is a curved plumbing fitting beneath a sink, shower, tub, or other fixture drain. The fitting holds a small amount of water in its bend, creating a seal that blocks sewer gases from entering the room. P-Traps also connect the fixture drain to the building’s drainage pipe.
Also called: Plumbing Trap, Sink Trap
Pipe Bursting is a trenchless sewer repair method that breaks an old buried pipe apart while pulling a new pipe through the same path. A bursting head travels through the existing line and pushes broken pieces into the surrounding soil. The method can replace a damaged sewer line with limited surface digging.
Also called: Pipe Splitting
Pipe Insulation is a protective covering fitted around plumbing pipes to slow heat loss and limit temperature changes. It can help keep hot water warmer, reduce condensation on cold pipes, and add protection against freezing conditions. Common materials include foam, rubber, and fiberglass, chosen to suit the pipe and its location.
Also called: Plumbing Pipe Insulation
A Pressure Reducing Valve is a plumbing control that lowers incoming water pressure to a safer, steadier level for a building’s pipes and fixtures. The valve uses a spring and diaphragm to respond to pressure changes. It helps limit stress on faucets, toilets, water heaters, appliances, and connected supply lines.
Also called: Pressure Regulator, PRV
PVC Pipe is a plastic plumbing pipe made from polyvinyl chloride. It carries wastewater, water, or other fluids through a building or buried line. PVC pipe resists rust and has smooth inner walls that support steady flow. Plumbers connect sections with fittings and solvent cement to create a continuous system.
Also called: PVC Plumbing Pipe
Sewer Belly is a low section in an underground sewer pipe where the pipe has settled or lost its proper slope. Wastewater and solids can collect in the dip instead of flowing freely. A sewer belly may cause repeated backups, slow drainage, or standing water inside the line, and camera inspection can help locate it.
Also called: Bellied Sewer Line, Sewer Sag
A Sewer Cleanout is an access point on a building’s drain line that lets a plumber reach the sewer pipe for clearing and inspection. The opening usually has a removable cap and connects to the underground line. Cleanouts may sit outside near the building, inside a utility area, or near a property line.
Also called: Cleanout, Drain Cleanout, Mainline Cleanout
A Shutoff Valve is a plumbing control that stops or allows water flow through a pipe. You can close the valve during a leak, fixture repair, or maintenance task. Common types include ball valves, gate valves, and fixture stops. The valve may serve one fixture, a branch line, or the whole building.
Also called: Main Water Shutoff, Stop Valve
Sump Pump Check Valve is a one-way valve installed in a sump pump discharge pipe. The valve lets pumped water flow away from the pit, then closes when the pump stops. This action keeps water from flowing back into the sump pit and reduces repeated pump cycling.
Also called: Sump Check Valve
A Tankless Heat Exchanger is the part of a tankless water heater that transfers heat to water as it flows through the unit. A burner or electric element heats the exchanger, and the exchanger warms the passing water. It does not store hot water, and it is not the complete water heater.
Also called: Tankless Water Heater Heat Exchanger
A Toilet Wax Ring is a flexible sealing gasket that sits between a toilet base and the drain flange. It seals the toilet’s waste outlet to help prevent water and sewer gas from escaping at the floor connection. The ring compresses as the toilet is secured, creating a close seal around the drain opening.
Also called: Toilet Seal, Wax Seal
A trap primer is a plumbing device that sends water into a drain trap to keep its seal intact. The water blocks sewer gas from moving through an unused floor drain. Trap primers connect to a water supply and may activate when nearby plumbing runs or when water pressure changes.
Also called: Floor Drain Trap Primer
A Vacuum Breaker is a backflow protection device that stops contaminated water from being pulled into a clean water supply. It admits air when water pressure drops and creates a vacuum. On a hose bib, the device helps protect household plumbing when a hose sits in a bucket, pool, or other water source.
Also called: Anti-Siphon Valve, Hose Bib Vacuum Breaker
A vent stack is a vertical plumbing pipe that carries sewer gases outside and lets air enter the drainage system. This airflow helps wastewater move through drainpipes and keeps water in traps. A vent stack usually extends through the roof and connects with drain lines inside the building.
Also called: Drain Waste Vent, Plumbing Vent
Water hammer is a pressure shock that occurs when moving water stops or changes direction suddenly. The shock travels through pipes and can create a banging or knocking sound. Repeated pressure shocks may loosen pipe supports, strain valves, or damage plumbing connections. Water hammer often points to a flow-control problem.
Also called: Hydraulic Shock
A Water Heater Element is an electric heating component inside a tank-style water heater. It transfers heat into the stored water when electricity passes through its metal casing. Most electric water heaters have an upper element, a lower element, or both. Gas water heaters do not use this component.
Also called: Heating Element
A water main is a buried pipe that carries treated water through a public or shared distribution system. It supplies smaller service lines that deliver water to homes, buildings, and other properties. A water main usually runs beneath a street, easement, or shared access area and connects to multiple properties.
Also called: Main Water Line
A water pressure gauge is a testing tool that shows the force of water inside a plumbing system. The gauge usually has a dial and connects to a hose bib, appliance connection, or test port. Plumbers use its reading to check pressure conditions and help identify pressure-related plumbing problems.
Also called: Pressure Gauge
Water Service Line is a buried pipe that carries potable water from a public water main or private supply to a building. It connects the outside water system to the property’s plumbing. The line may include an exterior shutoff, curb stop, meter connection, and the pipe leading to the building entry point.
Also called: Water Supply Line
Water Softener Resin is the ion-exchange material inside a water softener tank. The resin consists of small beads that attract calcium and magnesium from incoming water. The exchange reduces hardness as water passes through the tank. A brine rinse later removes the collected minerals and restores the resin for continued use.
Also called: Ion Exchange Resin
