TPR valves and the discharge pipes that love them

TPR sometimes means temporary price reduction, but not here. On a water heater, TPR means Temperature Relief Valve. It’s on the top of (or on the side of, near the top) of your water heater.

If the water heater malfunctions, pressure could build, temps could rise, or both. When water becomes steam, it expands to 1600 times it’s original size. You don’t want to be in the building if that happens.

The TPR valve is designed to open way before that happens. it will let any built-up pressure out long before the heater becomes a rocket.

A discharge pipe attached to the valve then directs pressurized water to a safe place, namely the floor. There are some rules about the discharge pipe that are important safety considerations.

  1. Be straight and short as possible.
  2. Terminate 1 1/2″ to 6″ from the floor.
  3. Be approved material (CPVC, copper, galvanized steel, stainless steel, polyethylene or polypropylene).
  4. Not be threaded at the end, or have T fittings.