ABS Acrylonitrile Butadiene Styrene: A rigid black plastic pipe used for drain, waste, and vent lines.
Aerator : A device screwed into the end of a faucet spout that mixes air into flowing water, and controls flow to reduce splashing. It sometimes contains a baffle to reduce flow to 2.5 gpm.
Air Lock : Blockage in the flow of liquid, esp. on the suction side of a pump caused by an air bubble in the line.
Angle Stop : A shutoff valve between the water pipes and a faucet. Its inlet connects to the water supply pipe in a wall, and its outlet angles up 90 degrees toward the faucet. These are usually used to shut off water to a fixture in case of an emergency repair rather than daily usage.
Anode Rod : A sacrificial rod installed in a water heater that protects the tank from corrosion, helping to extend the life of the tank.
Anti-Siphon : Preventive device for the backflow of liquid into a system. Used on sprinkler systems to prevent water from trickling back into the supply that is feeding it.