Glossary

These are the plumbing words used in this book, in plain English, so that you can follow a chapter or a plumber without having to stop and ask.

Action level: The concentration of a contaminant that, if exceeded, triggers treatment or other requirements for a water system. You will see it in the lead row of a water report.
Aerator: The small screen at the tip of a faucet that mixes air into the stream. It is the first place to look when one faucet runs weak.
Air cushion: A pocket of trapped air inside a water hammer arrestor that absorbs the pressure wave when a valve shuts.
Air gap: An open space between a drain line and the pipe it empties into, so that dirty water cannot be drawn back up.
Angle stop: The small valve under a sink or behind a toilet, where the supply comes out of the wall and turns toward the fixture. This book also calls these fixture stops.
Anode rod: A metal rod hung inside a water heater tank that corrodes so the tank does not. It is meant to be inspected and replaced.
Arrestor: A small device on a supply line that absorbs the shock of water stopping suddenly.
Backflow: Water running the wrong way in a pipe, which can draw dirty water back into the clean supply.
Ball valve: A valve with a drilled ball inside, opened or closed by a quarter turn of its handle.
Brine: The strong salt solution a water softener uses to clean its resin. It goes down a drain when the cycle ends.
Building drain: The large, lowest drain pipe in a house, which collects everything and carries it out toward the sewer or septic tank.
Cartridge: The replaceable part inside many faucets that controls the flow and mix of hot and cold.
Cast iron: A heavy metal pipe used for drains and stacks, common in older houses.
Chain: The short link between a toilet handle and the flapper. Too tight or too loose and the toilet misbehaves.
Cleanout: A capped opening in a drain line that gives access for clearing a blockage.
Consumer confidence report: The annual drinking water quality report that community water systems must send their customers by July 1.
Copper: A common supply pipe, penny colored, usually joined with solder.
CPVC: A rigid plastic supply pipe made of chlorinated polyvinyl chloride, with glued joints.
Curb stop: A valve on the service line near the street or property line. It belongs to the utility or a licensed pro; homeowners use the house valve.
Dip tube: The pipe that carries incoming cold water down to the bottom of a tank water heater.
Discharge pipe: The pipe that carries water away from a relief valve. It must never be capped or plugged, and what comes out of it can scald.
Drain valve: The valve near the bottom of a tank water heater used to draw water out.
Drainfield: The area of ground where a septic system lets liquid soak into the soil. Do not park or drive on it.
Fall: The downward slope of a drain pipe, usually given in inches per foot.
Fill valve: The valve in a toilet tank that lets water in after a flush and shuts off when the tank is full.
Fixture: Anything that uses water and drains it: a sink, a toilet, a tub or a shower.
Fixture stops: The small valves that shut the water off at one fixture, such as a sink or a toilet.
Flapper: The rubber seal at the bottom of a toilet tank that lifts to start a flush and drops to end it.
Float: The part in a toilet tank that rises with the water and tells the fill valve when to stop.
Flush valve: The opening at the bottom of a toilet tank through which water drops into the bowl. The flapper seals it.
Galvanized steel: Steel supply pipe coated with zinc and joined with threads, common in older houses. A magnet sticks to it.
Gpf: Gallons per flush, the measure of how much water a toilet uses. The federal standard is 1.6 gpf.
Gpg: Grains per gallon, a unit of hardness. One gpg is about 17 mg/L.
Gpm: Gallons per minute, the measure of how fast a faucet or showerhead runs.
Hard water: Water carrying a lot of dissolved calcium and magnesium.
Hose bib: An outdoor faucet with a threaded end for a hose. The diagrams in this book label it a hose faucet.
Hydrogen sulfide: A toxic gas in sewer gas with a rotten egg smell.
Lateral: The sewer pipe that runs from a house to the city main. Who owns it varies by city.
Lead-free: A legal term for plumbing materials: a weighted average of 0.25 percent lead on wetted surfaces of pipes and fittings, and 0.2 percent in solder and flux.
Main shutoff: The valve that stops water to the whole house. Find it before you need it.
Manifold: A fitting from which separate supply lines run to individual fixtures, often used with PEX.
MCL: Maximum contaminant level, the highest level of a contaminant allowed in drinking water.
MCLG: Maximum contaminant level goal, the level below which there is no known or expected risk to health, with a margin of safety.
Meter: The device that measures how much water the house uses. It is also a handy leak detector.
Mg/L: Milligrams per liter, the unit used for many water results, including hardness.
NSF/ANSI 53: The standard the CDC names for a filter certified to remove lead. It pairs that with NSF/ANSI 42 for particulates.
O-rings: Rubber rings that seal the moving parts of a faucet.
Overflow tube: The upright tube in a toilet tank that sends excess water into the bowl rather than onto the floor.
Permit: Permission from your town or county to do a piece of work, usually with inspections. The rules vary from place to place.
PEX: Cross-linked polyethylene, a flexible plastic supply pipe.
Point-of-entry: Water treatment installed where the line enters the house, treating all the water.
Point-of-use: Water treatment at one faucet or location, such as a pitcher or an under-sink filter.
Polybutylene: A flexible plastic supply pipe used in homes from 1978 to 1995, according to a Connecticut working group.
Pressure-reducing valve: A valve, also called a regulator, that lowers the street pressure to a level the house can live with. It sits on the customer's side of the meter.
Psi: Pounds per square inch, the measure of water pressure.
PVC: Polyvinyl chloride, a rigid plastic pipe with glued joints.
Refill tube: The small tube in a toilet tank that sends water into the overflow tube to refill the bowl.
Regeneration: The cycle in which a softener cleans its resin with brine and sends the waste down a drain.
Relief valve: The safety valve on a water heater that opens if temperature or pressure gets too high. Never cap, plug or remove it; a drip is a plumber call.
Reverse osmosis: A treatment that pushes water through a membrane with tiny pores, which stops many contaminants and can create a lot of wastewater.
Rim holes: The small holes under the rim of a toilet bowl that let flush water run down its sides.
Scale: The hard mineral crust left by hard water, especially when it is heated.
Scum: The layer of grease and light solids that floats at the top of a septic tank.
Sediment: Solid material that settles at the bottom of a water heater tank.
Septic tank: The buried tank that holds household waste and lets solids settle before liquid moves to the drainfield. Never enter it or lean into it.
Service line: The pipe that brings water from the street main to the house. It belongs to the utility or a licensed pro.
Sewer gas: The mix of gases from decaying waste. If the smell is strong or anyone feels ill, get out and call the fire department from outside.
Sludge: The heavy solids that settle to the bottom of a septic tank.
Softener: Equipment that removes hardness minerals by trading them for sodium or another ion. It is not a lead filter.
Stack: The large vertical pipe that carries drain water down and air up through a house.
Street main: The water utility's pipe under the street, which feeds the service lines.
Thermostatic valve: A valve that blends hot and cold water to hold a set temperature at the tap or shower, which guards against scalds.
Trap: The curved section of a drain that holds water to block sewer gas.
Trap arm: The section of drain pipe that runs from the trap to the drain and vent.
Trapway: The curved channel inside a toilet that holds the water seal and leads to the drain.
Vent: A pipe that lets air into the drain system, so that water can run freely and traps keep their water. It usually ends at the roof.
Water hammer: The bang in a pipe when water stops suddenly and a pressure wave travels back along the line.
Water seal: The water standing in a trap or toilet, which blocks sewer gas.
WaterSense: EPA's label for fixtures that meet its water-saving specifications.
Wax ring: The wax seal between the bottom of a toilet and the flange in the floor.