What Prevents a Water Heater Explosion? – TPR Valves & Failures

By February 14, 2020February 27th, 2020Plumbing
Water Heater TPR Valve Failures

This question can be better understood through, what is a TPR Valve on a water heater? A TPR Valve or Temperature/Pressure Relief Valve is how a water heater relieves interior pressure to prevent from explosion!

How does the TPR Valve Function and can it fail?

A TPR valve can definitely fail, in fact, it can be quite common for the TPR valve to be improperly installed and/or fail! As home inspectors, we see this happen quite frequently and it is imperative the valve be repaired to prevent further damage. So how does the TPR valve work?

A TPR valve uses pressure sensing, and temperature readings to allow water passage through the valve if the water inside the water heater becomes too hot or the pressure inside the tank becomes too high.

If discharge was to happen, it is important that the valve have a proper discharge tube attached to the unit. The water discharged from the water heater during a relief, can be steam or extremely hot, therefore, having a discharge straight discharge tube pointed to the ground can help prevent scalding on nearby people.

Properly Installed Temperature/Relief Valve & Discharge Tube

Let’s look into a TPR valve discharge tube:

A missing or improperly installed discharge tube is a common write-up amongst home inspections and four-point inspections. A discharge tube should be made out of: an approved material, such as CPVC, copper, polyethylene, galvanized steel, polypropylene, or stainless steel. Other plumbing piping can melt under the heat.

Moreover, a discharge tube should be hand-tight, and extend less than 6 inches away from the floor. The tube should never go in an upwards direction as it can prevent proper water flow and it is recommended the tube be visible so the homeowner can see if the valve is leaking.

There are MANY other restrictions and rules of install for discharge tubes and TPR valves. You can check out more information about installs on the NACHI article for TPR Valves and Discharge Tubes.

What to do if you believe your TPR valve is leaking/failing?

If your TPR valve is leaking, it might be time for replacement or further evaluation by a licensed plumber. The unit could be under too much pressure or the valve itself could just be failing. Either way, repairs are needed and are important for your safety!

Check your water heater and TPR valve as often as you can. Be sure the discharge tube is in a visible area so you can frequently check for moisture.

Have more questions about water heaters? Contact us! We perform home inspections of all types in the Greater Tampa Bay Area and are always available for a call to answer your questions.

Aaron Shishilla

Author Aaron Shishilla

Aaron Shishilla is the youngest registered professional inspector in Florida. Coming from a family-owned home inspection company and now the marketing manager at Waypoint.

More posts by Aaron Shishilla

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