Plumbing words, explained plainly

A sacrificial metal rod inside a tank water heater that corrodes in place of the steel tank. Once it is used up, the tank starts corroding instead.

The agency with legal authority over building work at a given address: for most homes in the service area, the city's building department; for unincorporated pockets, the county. The AHJ decides what needs a permit, what edition of the code applies, and what the inspector checks.

A capped access point on a drain or sewer line that lets a plumber run a cable, a jetter nozzle or a camera into the pipe without removing a fixture. Most houses have one outside at ground level near where the sewer lateral leaves the building.

Rigid metal water supply pipe joined by soldered or press fittings. The long-standing standard for residential water lines, and still used for repipes and for the visible connections at fixtures and water heaters.

A motor-driven steel cable with a cutting or retrieving head that a plumber feeds down a drain to break up or pull back a blockage. Also called a rooter machine, an auger or simply snaking.

Finding a hidden water leak with instruments instead of exploratory demolition: acoustic listening equipment that hears water escaping a pressurized line, pressure testing to isolate which line is losing water, and related tools to narrow the location to a small area.

Steel water pipe with a zinc coating, common in older homes. Over decades the zinc wears away and the inside rusts and narrows, which shows up as rusty water, weak pressure and leaks at the threads.

Checking gas piping for leaks with combustible-gas detection along the run and a pressure test that isolates the section holding the leak. It identifies exactly what to repair instead of replacing the whole system.

A tank on a commercial kitchen's drain line that slows the flow so fats, oils and grease separate and float, and solids settle, before wastewater continues to the sewer. It has to be pumped and the lines downstream of it still collect grease.

Water carrying dissolved calcium and magnesium. It leaves scale on fixtures, glassware and heating surfaces, shortens water heater life, and makes soap work less well. Hardness is measured by a water test, not guessed from a spot on a glass.

A pump and return line (or a crossover valve) that keeps hot water moving through the pipes so it arrives at the tap quickly instead of after a long wait. Common in larger homes and in commercial buildings.

Cleaning a drain or sewer line with a high-pressure stream of water from a specialized nozzle. Instead of punching through the blockage, jetting scours grease, scale, sludge and roots off the full inside diameter of the pipe.

The valve that stops all water coming into the house. Usually near the front hose bib, in a garage wall, or at the street meter box. Turning it clockwise until it stops isolates the house from the supply.

The U-shaped bend under a sink, tub or shower that holds a plug of water. That water seals the drain so sewer gas cannot come up into the room. A dry or broken trap is the usual reason a drain smells.

Cross-linked polyethylene tubing, a flexible plastic water supply pipe joined with crimp, clamp or expansion fittings. Widely used for repipes because it can be snaked through walls with fewer joints than rigid pipe.

A very small hole that opens in a copper water line from internal pitting. It sprays or weeps rather than gushes, so it is often found by a stain, a warm spot, or a rising water bill rather than by sight.

A low spot in a drain or sewer line where the pipe has settled below its proper slope. Water and solids collect in the sag instead of flowing through, so the line clogs repeatedly in the same place.

A trenchless replacement method that pulls a bursting head through the old sewer pipe, breaking it outward, while dragging a new pipe into the space behind it. It replaces the line rather than lining it, still through access pits at each end.

The site visit by the AHJ's inspector that verifies permitted work matches the adopted code before it is closed in or put into service. A failed inspection means a correction and a re-inspection, not a fine.

Authorization from the local building department to perform specified plumbing work, followed by an inspection that confirms the work meets the adopted code. The contractor applies for it, the city issues it, and the inspector signs it off.

A valve on the main water line that reduces the utility's street pressure to a safe pressure for the house. When it fails, pressure can climb high enough to stress every fixture, appliance and pipe joint in the building.

Isolating a section of water or gas piping, pressurizing it, and watching a gauge to see whether the pressure holds. A drop means the section is losing water or gas somewhere.

A foundation where the floor is built on posts, piers or perimeter walls above the ground, leaving a crawl space. Water and drain lines run in that crawl space rather than under concrete.

Replacing the water supply piping throughout a house with new pipe, usually because the existing pipe is failing everywhere rather than in one place. The old lines are abandoned or removed and new lines are run to every fixture.

A drinking-water system, usually under the kitchen sink, that pushes water through a fine membrane to remove dissolved solids and many contaminants, then stores the treated water in a small tank for a dedicated faucet.

Tree and shrub roots growing into a sewer or drain line through a joint or crack. Roots follow the moisture, then thicken inside the pipe until they catch paper and solids and cause a backup.

The single pipe that carries all of a building's wastewater from the house to the city sewer main in the street. Every drain in the house eventually joins it, which is why a lateral problem shows up as several fixtures backing up at once.

A leak in a water or drain line that runs beneath a concrete slab foundation. Because the pipe is under the floor, the water goes into the soil or up through the slab rather than dripping where you can see it.

A foundation where the house sits directly on a poured concrete slab, with water and drain lines run beneath or within the concrete. There is no crawl space under the floor.

Replacing only the failed section of a sewer line, located by camera and marked on the surface, instead of the whole run. The rest of the lateral stays in service.

The temperature and pressure relief valve on a water heater. It opens automatically if the tank gets too hot or the pressure climbs too high, discharging water through a drain line so the tank cannot rupture.

A storage water heater that keeps a tank of water hot and ready, reheating it as it cools or as hot water is drawn off. Gas and electric versions exist; the tank, its lining and its anode rod are the parts that determine how long it lasts.

A water heater that heats water on demand as it flows through a heat exchanger, with no storage tank. It supplies hot water continuously at its rated flow, and its size is chosen by the number of fixtures that may run at once.

Rehabilitating a sewer lateral from inside the existing pipe, through small access pits, instead of digging a trench along its length. A resin-saturated liner is installed and cured to form a new pipe inside the old one.

Running a waterproof camera on a push rod through a drain or sewer line and watching the inside of the pipe on a screen. It shows the blockage, the pipe condition and the location of any break, belly or root intrusion before a repair is quoted.

Draining sediment out of a tank water heater, or circulating a descaling solution through a tankless heat exchanger, to remove the mineral build-up that reduces efficiency and shortens the unit's life.

A simple check for a hidden leak: turn off every fixture and appliance, then watch the water meter. If the low-flow indicator or the dial keeps moving, water is leaving the system somewhere.

An ion-exchange unit that removes the calcium and magnesium that make water hard, swapping them for sodium on a resin bed that regenerates with salt. It treats the whole house at the main line.

A filter or filter set installed on the main line so every fixture in the house gets treated water. Typical stages handle sediment and chlorine, with taste and odor as the result most people notice.