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Glossary

Phoenix Plumbing Glossary

Plain-English definitions of the parts, valves, and terms that come up when you're dealing with a Phoenix plumbing system. Written by licensed plumbers.

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Water Treatment

Activated Carbon Filter

An activated carbon filter cleans water by adsorption, where contaminants stick to the surface of treated carbon. It removes chlorine, bad taste, odor, and many organic compounds. It comes as loose granular carbon or a solid carbon block, and it is common in whole-house units, under-sink filters, and reverse osmosis systems.

Traps and Vents

Air Admittance Valve

An air admittance valve, also called an AAV or Studor vent, is a one-way mechanical vent. It opens to let air into the drain system when suction develops, protecting the trap seals, then closes by gravity to keep sewer gas out. It is used where a normal vent through the roof is impractical.

Traps and Vents

Air Gap

An air gap is an open vertical space between a water outlet and the flood-level rim of the fixture below it, such as the gap between a faucet spout and the sink rim. That open space physically blocks dirty water from being siphoned back into the clean water supply, making it the simplest and strongest form of backflow protection.

Pipes and Supply Lines

Angle Stop

An angle stop is the small shutoff valve where a fixture's water supply line meets the pipe coming out of the wall, found under sinks and behind toilets. It lets you shut off water to that one fixture without touching the rest of the house. Plumbing code requires a shutoff at most fixtures.

Anode Rod

An anode rod is a sacrificial metal rod inside a water heater tank that corrodes in place of the tank's steel lining, protecting it from rust. Made of magnesium, aluminum, or zinc, it slowly dissolves through electrochemical corrosion and needs periodic inspection and replacement to keep protecting the tank.

Pipes and Supply Lines

Ball Valve

A ball valve is a shutoff valve that uses a rotating ball with a hole through it to start or stop water flow. A quarter turn of the handle, 90 degrees, goes from fully open to fully closed. Ball valves are reliable, quick to operate, and less likely to seize or leak than older washer-style valves.

Water Treatment

Brine Tank

A brine tank is the smaller second tank on a water softener. It holds the salt that dissolves into a strong salt water solution called brine. During regeneration, the softener draws this brine through its resin bed. The brine rinses hardness minerals off the resin beads and recharges them so the softener can keep removing hard water.

Building Sewer

A building sewer is the part of a home's drain system that starts about 2 feet outside the building wall and carries waste to the public sewer or a septic tank. It picks up where the building drain, the piping inside the house, ends. Code sets that boundary.

Pipes and Supply Lines

Check Valve

A check valve is a one-way valve that lets water flow in a single direction and closes automatically to block it from flowing back. It works on pressure alone, with no handle. Plumbing code requires one on sump pump and sewage ejector discharge lines to stop pumped water from draining back into the pit.

Closet Bend

A closet bend is the long-sweep 90-degree drain elbow under a toilet. It turns waste from straight down to sideways and carries it into the drain line. It is often a 4-inch by 3-inch reducing size. It sits below the closet flange and wax ring, out of sight.

Closet Flange

A closet flange is the pipe fitting that anchors a toilet to the floor and joins it to the drain. Bolts hold the toilet to the flange. A wax ring sits on top of the flange to seal the gap. It is also called a toilet flange or closet ring.

Corporation Stop

A corporation stop is the first valve on a home's water service line. It is tapped directly into the city water main on the utility side. It lets a plumber start a new service line without shutting off the main. Water then flows on to the curb stop and the meter.

CSST (Corrugated Stainless Steel Tubing)

CSST, or corrugated stainless steel tubing, is a flexible gas pipe used to carry natural gas or propane to appliances. Its bendable stainless steel wall installs faster than rigid black iron pipe. Traditional yellow CSST must be bonded to the home's grounding system to lower the risk of lightning damage.

Curb Stop

A curb stop is the water utility's shutoff valve for one property. It sits underground near the property line, inside a small curb box, and is turned with a long tool called a curb key. The utility uses it to shut off a home's water without affecting the street main.

Dip Tube

A dip tube is the long plastic tube inside a tank water heater that carries incoming cold water down to the bottom, where the burner or element heats it. This keeps cold water from mixing with the hot water waiting at the top, so you get full hot-water output until the tank runs low.

Traps and Vents

Drainage Fixture Unit (DFU)

A drainage fixture unit, or DFU, is the number plumbing code assigns to each fixture to represent how much wastewater it sends into the drain system. Plumbers add up the DFUs on a pipe, then use a code table to pick the drain size. It measures load, not gallons per minute.

Traps and Vents

Drum Trap

A drum trap is an old cylindrical drain trap shaped like a can, once installed under bathtubs in homes built before the 1960s. It holds a large pool of water as its seal. Drum traps clog easily, are hard to clean, and are no longer allowed for new work under modern code.

Escutcheon

An escutcheon is the decorative trim plate that covers the hole where a pipe or valve stem passes through a wall or floor. You see them behind a faucet handle, around a shower arm, and at a toilet supply line. The job is to look neat, not to seal.

Faucet Aerator

A faucet aerator is the small screened tip that screws onto the end of a faucet spout. It mixes air into the water stream, which produces a steady, splash-free flow while using less water. Aerators are a simple, cheap way to cut water use, and a clogged one is a common cause of weak flow at a single faucet.

Traps and Vents

Flood-Level Rim

A flood-level rim is the top edge of a fixture where water would spill over if the drain clogged, such as the rim of a sink or the overflow point of a toilet. Plumbing code uses this line as the reference for backflow protection, measuring the required air gap above it to keep dirty water out of the supply.

Pipes and Supply Lines

Galvanic Corrosion

Galvanic corrosion is the rapid rusting that happens when two different metals, such as copper and steel, touch in the presence of water. The water acts like a battery, and the more reactive metal corrodes fast at the joint. Plumbing code requires a dielectric fitting to separate dissimilar metals and stop it.

Gas Pressure Regulator

A gas pressure regulator is a valve that lowers gas pressure to the level an appliance needs and holds it steady. Gas leaves the utility line at a higher pressure than a furnace, water heater, or range can safely use. Regulators sit at the meter and often at each appliance.

Pipes and Supply Lines

Gate Valve

A gate valve is an older style of shutoff valve that raises and lowers a solid wedge, or gate, to open and close a water line. You turn a round handle several full turns to work it. Gate valves seal well when new but tend to seize or leak with age, so plumbers now favor ball valves for shutoffs.

Globe Valve

A globe valve is a valve made for throttling, or regulating how much water flows, rather than simple on-off shutoff. A disc moves up and down onto a ring seat, and water winds through an S-shaped path. That control comes with a higher pressure drop than a gate or ball valve.

Heat Trap

A heat trap is a device on a water heater's hot and cold connections that stops heated water from drifting up and out of the tank when no one is using it. Usually a pair of special nipples with an internal ball, it blocks the slow heat loss called convection, cutting standby energy waste.

Pipes and Supply Lines

Hose Bibb

A hose bibb is the outdoor faucet on the side of a house that a garden hose threads onto, also called a sillcock or wall hydrant. Plumbing code requires each one to carry a vacuum breaker, which stops contaminated water from being siphoned back into the home's drinking water.

Hot Water Recirculation Pump

A hot water recirculation pump moves hot water through the pipes so it is already warm at the tap, cutting the wait and the water wasted running the faucet. A demand-controlled pump runs only when triggered, returning the cooled water to the heater instead of letting it drain away.

Water Treatment

Ion Exchange Resin

Ion exchange resin is the bed of tiny plastic beads inside a water softener that actually softens the water. The beads are negatively charged, so they grab positively charged hardness ions like calcium and magnesium and release sodium in their place. A salt brine recharges the beads.

Meter Yoke

A meter yoke is the rigid bracket that holds a water meter inside the meter box. It keeps the inlet and outlet pipes at a fixed spacing and braces them. This lets the utility set or pull a meter fast. It is also called a meter setter.

Pipes and Supply Lines

No-Hub Coupling

A no-hub coupling is a stainless steel band that wraps a neoprene gasket to join two pipes end to end. It connects hubless cast iron drain, waste, and vent pipe without a torch or lead. Made to CISPI 310 and ASTM C1277, it is common in Phoenix cast iron repairs and repipes.

Oil-Water Separator

An oil-water separator is a device that removes oil, grease, and flammable liquids from wastewater before it reaches the sewer. It uses gravity so lighter oil floats to the top while water flows out below. Auto shops, garages, and car washes need one to keep petroleum out of the drain system.

Pipes and Supply Lines

PEX Manifold

A PEX manifold is a central hub that splits a home's incoming water into separate PEX lines, one running straight to each fixture. Because every fixture has its own line and its own shutoff at the manifold, this home-run layout lets you isolate one fixture without shutting off the rest of the house.

Pipes and Supply Lines

Push-Fit Fitting

A push-fit fitting, also called push-to-connect, joins two pipes by simply pushing them in, with no soldering, gluing, or crimping. Inside, a stainless-steel grip ring holds the pipe and an O-ring seals it. Listed push-fit fittings are code-approved and work across copper, PEX, and CPVC, making them popular for fast repairs.

Water Treatment

Reverse Osmosis Membrane

A reverse osmosis membrane is the semipermeable thin-film composite layer at the heart of an RO system. Water is pushed through it under pressure. The membrane lets water molecules pass while rejecting dissolved salts, minerals, and other TDS. It is the cartridge that slowly fouls and eventually needs replacing to keep the system working.

Pipes and Supply Lines

Saddle Valve

A saddle valve is a small clamp-on valve that taps a water line by driving a piercing pin through the pipe wall, often used to feed a fridge ice maker or a filter. It is quick and cheap, but it leaks often and many plumbing codes prohibit it, so plumbers replace it with a proper tee and shutoff.

Sand Interceptor

A sand interceptor is a below-floor tank that settles out sand, grit, and heavy solids from wastewater before it enters the sewer. The heavy material sinks and cleaner water flows out the top. Car washes, garages, and industrial floors use one to keep grit from clogging the drain lines.

Sanitary Tee

A sanitary tee is a drain fitting with a gentle curved sweep. It is used to turn drainage flow from a horizontal pipe into a vertical pipe. The sweep guides waste downward so it does not clog. It is different from a wye, which is used for other turns.

Water Treatment

Sediment Filter

A sediment filter is a mechanical pre-filter that strains sand, silt, rust, and other solid particles out of water. It uses a spun, pleated, or string-wound cartridge rated in microns. Placed ahead of softeners, carbon filters, and reverse osmosis, it protects that equipment and your fixtures from grit.

Pipes and Supply Lines

Sediment Trap (Drip Leg)

A sediment trap, also called a drip leg or dirt leg, is a short capped section of pipe that hangs down from a gas line just before an appliance. It catches rust, scale, and debris carried in the gas so that grit cannot reach and clog the appliance's gas valve or burner. Fuel gas code requires one at most appliances.

Sewage Ejector Pump

A sewage ejector pump lifts wastewater and sewage from a fixture below the sewer line, such as a basement bathroom, up to the gravity sewer main. It sits in a sealed pit and passes solid waste, unlike a sump pump, which only moves clean groundwater.

Stop-and-Waste Valve

A stop-and-waste valve is a shutoff valve with a small built-in drain port. Closing it stops the water and lets you drain the pipe past the valve. That prevents a trapped pipe from freezing and bursting. It is common on outdoor faucet and sprinkler lines in cold weather.

Water Treatment

TDS Meter

A TDS meter is a small handheld device that measures Total Dissolved Solids in water and shows the result in parts per million. It works by reading the water's electrical conductivity, not by identifying specific contaminants. Plumbers use it to check how well a reverse osmosis system or water softener is performing.

Temperature and Pressure Relief Valve (T&P Valve)

A temperature and pressure relief valve, or T&P valve, is the safety valve on a water heater that opens automatically if the tank gets too hot or the pressure climbs too high. It dumps water to relieve the buildup, preventing the tank from bursting. Code sets it to open near 210 degrees or 150 psi.

Thermostatic Mixing Valve

A thermostatic mixing valve blends hot water from the heater with cold water to deliver a safe, steady temperature at the tap. It reacts instantly to supply changes to prevent scalding. It also lets a water heater run hotter to store more usable hot water and fight bacteria, while still sending out tempered water.

Traps and Vents

Trap Primer

A trap primer is a small automatic valve that feeds a little water to a floor drain trap now and then. That keeps the trap seal full so sewer gas cannot rise into the room. Primers are common on seldom-used floor drains in commercial restrooms, mechanical rooms, and restaurants.

Traps and Vents

Trap Seal

A trap seal is the small plug of standing water held in the curved bend of a plumbing trap, such as a P-trap under a sink. That water blocks sewer gas from rising through the drain into the room. Plumbing code requires the seal to be between 2 and 4 inches deep.

Water Treatment

UV Water Disinfection System

A UV water disinfection system is a point-of-entry unit that passes water past a UV-C lamp to inactivate bacteria, viruses, and protozoa by damaging their DNA. It kills germs without chemicals but does not remove chemicals or sediment, so it needs pre-filtration. It is common for treating well water.

Pipes and Supply Lines

Vacuum Breaker

A vacuum breaker is a backflow-prevention device that lets air into a water line the moment pressure drops, breaking the suction that would otherwise siphon dirty water back into the clean supply. It is the small threaded device on outdoor faucets and the anti-siphon part built into many irrigation and utility valves.

Traps and Vents

Vent Stack

A vent stack is a vertical pipe in a plumbing system's drain-waste-vent network that supplies outside air to the drainage pipes so trap seals aren't pulled dry by suction. It connects near the base of a drainage stack and runs up through the roof, distinct from a stack vent, which extends a soil or waste stack upward.

Pipes and Supply Lines

Water Hammer Arrestor

A water hammer arrestor is a small device installed near a quick-closing valve, such as a washing machine's, that absorbs the pressure surge created when water flow stops suddenly. A sealed piston and gas chamber cushion the shock, preventing the loud banging noise and pipe damage known as water hammer.

Water Meter

A water meter is the device a utility uses to measure how much water a home uses. Most home meters are positive-displacement types that fill and empty a fixed chamber, like a nutating disc or oscillating piston. A dial called the register shows the total. You can also use it to spot leaks.

Wax Ring

A wax ring is a donut-shaped seal, made of pure petroleum wax, placed between a toilet's base and its floor flange. It compresses when the toilet is set in place, creating a watertight, airtight seal that stops leaks and blocks sewer gas from entering the bathroom. It is designed for single use.

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