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Temperature Pressure Relieve (TPR) valves are installed on water heaters as a safety device to prevent water heaters from exploding. Building codes require that a TPR valve be installed.

If you haven’t seen a water heater explode before, check out the short video below:

Water Heater Explosion Video

TPR valves are designed to open when the pressure exceeds 150 psi or 210 degrees F.

These limits are set very low relative to the actual pressure it takes to explode a water heater.

In this Myth Busters video, the pressure in the tank can exceed 330 psi before it will explode. The TPR valve will relieve pressure long before it becomes dangerous.

So, if the TPR valve is missing, is it a big deal? Will the water heater explode today if we turn it on?

Water heaters are designed to be safe. If the water heater is new, the risk of explosion is low. As the water heater ages, the risk of explosion increases. The life expectancy on water heaters is 8 to 12 years.

TPR valves are cheap and the installation is not very expensive. Total cost for parts and professional installation by a licensed plumber is between $150 and $300 dollars.

Homeowners can also install TPR valves themselves for about $20. There are videos and instruction manuals to guide the homeowner in correctly installing a TPR valve.

TPR valves can be installed either on the top or the side of a water heater. They should always have a drain line connected to the valve instead of being left open as shown below.

TPR Valve
TPR Valve Drain Line Connected

The drain line can be routed to either the sewage system (rare), outside the building, or within 6 inches of the overflow pan as shown below.

Drain Line Rerouted


  • A missing TPR valve on a water heater is NOT a cause for alarm.
  • It is an issue that needs to be addressed.
  • The cost of installation is cheap. Water heaters can be lethal.
  • Cost of installation can run between $150 and $300. This is a low cost precaution that can save lives and thousands of dollars on a home repair.
  • This is a job for those who enjoy DIY. Retail cost of a TPR valve is about $20.