DEFECT: Water Heater Temperature & Pressure Relief (TPR)
The water heater Temperature & Pressure Relief Valve (TPR) and associated piping is a critical safety feature of a water heater. The purpose of the TPR valve is to relieve the pressure in the water heater in the event of a runaway thermostat or other overpressure situation.
Typically water boils at 212 degrees Fahrenheit, under pressure this boiling point goes up and can be quite high inside the pressurized water heater tank. As the temperature of the water goes up, the pressure in the tank increases causing a very dangerous situation. If the pressure in the tank exceeds the burst point and ruptures, the superheated water instantly flashes to steam when it returns to normal atmospheric pressure. The result is an immediate release of a tremendous amount of energy which will most likely result in a catastrophic explosion of the water heater.
The job of the TPR valve is to relieve the pressure in the water heater when it either reaches 210 degrees Fahrenheit or when the pressure in the tank exceeds 150 PSI.
To prevent injury and damage to the structure, this valve must be properly plumbed to the exterior and within about 6 inches from the ground. The most typical material used for this piping is solid copper pipe, there are some other materials allowed for use but these are limited. This pipe cannot have any valves other than the TPR, there cannot be any threads at the outlet that would allow a cap to be installed, there cannot be any flexible pipe. There are numerous other restrictions on the installation of this pipe that are beyond the scope of this article. Any repairs or replacement of the TPR valve or pipe should be made by a qualified plumber.
If your TPR line is disconnected or damaged, you should get it repaired immediately. Serious injury or death can occur if this valve is disconnected. If a person happened to be in the room when this valve activated, they could be severely burned by the scalding water and steam that escaped.
If you ever notice water leaking from the outlet of the TPR line it means one of two things.
- The TPR valve is leaking
- The TPR valve has activated due to an overheat or overpressure situation.
The first thing you should do if you see the TPR dripping is to shut off the water heater and call a plumber to diagnose and repair the problem.
This information was provided courtesy of Southwest Premier Home Inspection, LLC. Reproduction in any form is not permitted without consent. Copyright 2008-2010 Southwest Premier Home Inspection, LLC.
Southwest Premier Home Inspection is the Phoenix Arizona Home Inspection leader. To find out more visit our Phoenix Home Inspection website www.swpHomeInspect.com
