The water heater is a device that’s responsible for warming the water inside your home. Most water heaters have a tank. Cold water will enter through the bottom of this tank where it’s heated via an electric or gas heating element. Aside from a heating element, though, water heaters contain several other components, one of the most important being a temperature and pressure (T&P) valve. What is a T&P valve exactly?

The Basics of T&P Valves

A T&P valve is a water heater component that’s designed to protect the equipment from damage caused by excess pressure. You can usually find it at or near the top of the tank. The T&P valve has a lever that you can lift to release excess pressure.

Importance of the T&P Valve

Water heaters create pressure as a byproduct of warming water. Most water heaters, in fact, hold roughly 150 pounds per square (PSI) of pressurized water. As they warm the water, the water will undergo thermal expansion, meaning it will become pressurized inside of the tank. The T&P valve is a safety mechanism that protects against the buildup of excess pressure.

Your water heater will still create pressure with a T&P valve. The T&P valve simply acts as a failsafe in the event of excess pressure. If your water heater exceeds the PSI for which it’s rated, the T&P valve will open. As a result, the excess pressure will be released in the form of steam and hot water through the discharge pipe. The T&P valve will then close once the pressure drops back to a normal level.

Signs of a Bad T&P Valve

If the T&P valve is bad, pressure may build up inside of your water heater to dangerous levels. There’s only so much pressure your water heater can hold. If it exceeds this limit, it may explode.

While T&P valves typically last for many years, they can still fail. Most failures involve the T&P valve staying either opened or closed. If the T&P valve stays open, your water heater won’t be able to retain pressure. As soon as the hot water expands, it will be released through the discharge pipe.

If the T&P valve stays closed, pressure will continue to build up inside of your water heater. This may result in a rupture along one of the seams. If you notice water leaking from a seam on your water heater, it could be a sign of a bad T&P valve.