This article below is from The ASHI Reporter. Homeowners need to know the seriousness of maintaining the water heater. Retrofitting or installing TPR valves can prove disastrous & dangerous.

The most important part of your client’s domestic hot water system

“The steam-powered tank hurtled across the busy intersection at First Avenue South and South 152nd Street — over at least six lanes of traffic — before landing more than 439 feet away in the parking lot of a Pizza Hut.”

This excerpt from a July 28, 2001, article in the Seattle Post-Intelligencer describes what happened when a water heater with a capped Temperature Pressure Relief (TPR) valve overheated and exploded.

High limit controls

Water heaters have thermostatically controlled devices that keep them from overheating. Both gas and electric water heaters have temperature-limiting devices that shut off the energy source when their regular thermostat fails. Electric heaters have a high-limit switch that interrupts the power when overheating occurs. Many of us have seen and perhaps reset the device by pushing a small red button under the cover plate and just above the thermostat dial.

Thermostatically controlled gas valves found on most residential gas water heaters have a safety shutoff built into the gas valve itself. When they react to excessive temperature, the gas flow to the burner is stopped. Generally not resettable, the entire control valve has to be replaced to get the water heater up and running again.

These devices are the first line of protection against water heater explosion. Should they fail, a temperature pressure relief valve, which should be installed within the top 6 inches of the tank, should prevent the heater from suddenly becoming a bomb or launching like a rocket. In both of the explosion events described earlier, it appears a properly installed TPR valve would have prevented the carnage.