Water Heater Safety - The TPR Valve

Installed on your water heater is a safety device, the TPR valve (short for Temperature / Pressure Relief Valve).

If the water heater malfunctions, the temperature and pressure of the water inside the water heater can reach dangerous levels. If the pressure in the tank gets too high, the tank can rupture, causing an uncontrolled release of the contents of the tank. Tanks that have failed in this way have caused considerable damage to structures.

Before the contents of the tank reach dangerously high temperatures and pressures, the TPR valve opens, relieving water and steam from the tank to prevent a dangerous tank failure.

In order to operate as designed, TPR valves must be properly installed on the tank, and should also have a pipe on the outlet side of the valve that goes to about 6-12" of grade. The pipe on the outlet of the TPR valve should also meet certain requirements:

- The pipe should be directed downward, in order to minimize discharging steam directly at any occupants nearby.

- The pipe should slope downward and discharge in a visible location, so that if the valve starts to fail (eg. leak), the leak is noticable and the valve can be serviced or replaced.

- The pipe diameter should match that of the valve, so that the pipe does not constrict the flow of water and steam exiting the tank.

- The pipe should not be threaded on the end near grade. This prevents a homeowner from attaching a valve that could hide a pesky drip caused from a failing TPR valve.

- Lastly, the pipe should be made of a material (such as copper) capable of handling the high temperatures and pressures of any potential release.

If your TPR valve has discharged or leaks, is not properly installed on the tank, or has an improper or missing discharge pipe, you should have it adressed by a qualified plumbing contractor.