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When you call a plumber or read an estimate, the vocabulary can feel like a foreign language. What’s the difference between a P-trap and a cleanout? What does “water hammer” mean? Why is the plumber asking about your PRV?
This glossary covers the plumbing terms Atlanta homeowners encounter most often — defined plainly, without the jargon.
Supply System Terms
Main shutoff valve — The valve that controls water flow into the entire home. Knowing where this is located is essential for any plumbing emergency. Typically found where the supply line enters the house — near the foundation, in a crawlspace, or in a utility area.
Pressure reducing valve (PRV) — A valve installed on the main supply line that reduces incoming municipal water pressure to a safe range (typically 50 to 75 PSI). When it fails, pressure throughout the home may drop dramatically or become erratic. Found near the main shutoff.
Water hammer — The banging sound you sometimes hear in pipes when a faucet is turned off quickly. Caused by the sudden stop of fast-moving water. Chronic water hammer can stress pipe joints over time. Usually addressed with water hammer arrestors or by adjusting water pressure.
Expansion tank — A small tank added to the supply system to absorb pressure changes in closed plumbing systems. Required by code in many Atlanta-area jurisdictions, particularly when a backflow preventer is installed. Often found near water heaters.
Backflow preventer — A device that prevents water from flowing backward in the supply system — important for protecting the potable water supply from contamination from irrigation systems, water heaters, or other connections.
Drain System Terms
P-trap — The curved pipe section under every sink, shaped like the letter P. It holds a small amount of water that creates a seal preventing sewer gases from entering the home. If a sink drain smells like sewage, the P-trap may have dried out (common in guest bathrooms that don’t get used regularly) or failed.
Cleanout — A capped pipe access point in the drain or sewer system that allows a plumber to insert a snake or camera. Exterior cleanouts are typically located in the yard along the path of the sewer line. Interior cleanouts are often in utility areas or basements.
Drain field (or leach field) — For homes on septic systems, this is the underground network where treated wastewater disperses into the soil. Not applicable to homes on Atlanta’s public sewer system.
Vent stack — The vertical pipe that runs from the drain system up through the roof. It allows air into the drain system so water can flow freely (without air, you’d hear gurgling and drains would empty slowly). Blocked vent stacks — from leaves, bird nests, or debris — cause sluggish drains throughout the home.
Hydro-jetting — A drain cleaning method that uses high-pressure water (typically 4,000 PSI or more) to scour pipe walls, removing grease, mineral buildup, and roots more thoroughly than a snake. Standard service for kitchen drain lines and sewer lines with heavy buildup.
Water Heater Terms
Anode rod — A sacrificial metal rod inside tank water heaters that corrodes instead of the tank wall, extending the tank’s lifespan. When the anode rod is fully depleted, the tank itself begins to corrode. Replacement every three to five years significantly extends water heater life.
TPR valve (temperature and pressure relief valve) — A critical safety device on every water heater. It releases water if temperature or pressure inside the tank becomes dangerously high. The discharge pipe from a TPR valve should always route to the floor or outside — if it’s capped or missing, that’s a safety issue.
Tankless water heater — A water heater with no storage tank that heats water on demand as it passes through a heat exchanger. Longer lifespan, better efficiency, unlimited hot water. Requires upfront installation work for gas line and venting sizing. See our tankless water heater page for more.
Hybrid water heater — An electric water heater that uses heat pump technology to extract heat from surrounding air rather than creating heat through resistance elements. Two to three times more efficient than a standard electric heater. See our hybrid water heater page for details.
Toilet Terms
Flapper — The rubber seal at the bottom of the toilet tank that opens to release water during a flush and closes to allow refilling. The most common cause of a running toilet is a worn or warped flapper that no longer seals properly.
Fill valve (ballcock) — The valve that refills the toilet tank after a flush, controlled by a float. Older toilets have a ballcock style with a ball float on an arm; modern fill valves use a cup float that slides up and down the valve shaft.
Wax ring — The wax seal between the toilet base and the floor flange that creates a watertight connection to the drain. When this seal fails, water can leak at the base of the toilet during flushing. Replacement requires removing the toilet.
Gas System Terms
Gas shutoff — Every gas appliance should have a dedicated shutoff valve within a few feet of the appliance. Know where each one is. The main gas shutoff for the home is typically at the meter.
Flexible gas connector — The corrugated metal hose that connects a gas appliance to the rigid gas supply line. These have a lifespan and should be inspected periodically. Uncoated brass connectors are no longer approved in most jurisdictions; coated stainless steel connectors are standard.
Gas pressure test — A procedure where a plumber pressurizes a gas line and monitors for pressure drop to confirm there are no leaks. Required after any new gas line work is completed, before the system is put into service.
Other Common Terms
Sewer camera inspection — A diagnostic procedure where a camera is run through the sewer line to assess condition, identify blockages or root intrusion, and pinpoint problems before they cause failures. See our sewer camera page.
Water filtration system — Any system that removes contaminants from the water supply, from simple under-sink filters to whole-house systems. Types include carbon filters, reverse osmosis, and UV treatment. See our water filtration page for what makes sense for Atlanta water.
Plumbing inspection — A systematic evaluation of a home’s entire plumbing system by a licensed plumber — supply lines, drain lines, water heater, fixtures, gas connections, and pressure. Recommended before purchasing a home and every few years in older properties. See our plumbing inspections page.
Still have questions about something you read in an estimate or heard from a plumber? Call Fix and Flow at (404) 800-FLOW — we’re happy to explain anything before you commit to a repair.