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Hot Water Unit

How to test a hot water unit temperature and pressure relief valve

Every hot water unit should be equipped with a temperature and pressure relief valve.

This is a crucial safety device that is mandated by all plumbing codes and it should never be removed or disabled.

In this article we will discuss problems that sometimes occur with the temperature and pressure relief valves on the water heaters.

Hot water unit temperature and pressure relief valve

Relief valves discharge for usually two reasons: one, there’s excessive pressure building up inside the system that has exceeded 150 pounds of pressure or two, the temperature inside the tank has exceeded 210 degrees Fahrenheit. Both of these situations can be very dangerous and the temperature and pressure relief valve will open to prevent an explosion.

If you notice water on the floor around the water heater and there’s no evidence of a tank or plumbing leak, it is probably a sign that the water heater’s temperature and pressure relief valve has recently opened and relieved itself.

First, you should test the water pressure in the house by using a pressure gauge that you will screw right onto a hose bib or a faucet. You could pick up one of these gauges at any home centre. Most plumbing codes state that the maximum water pressure coming into the house should be 80 PSI or less.

If the water pressure exceeds this amount, a pressure reducing valve will need to be installed on the water main. Note that the ideal water pressure is between 50 and 60 PSI. You want to make sure that the thermostat is not set too high.

If the thermostat is set too high or if it’s faulty, the T&P valve will discharge to relieve the pressure inside the tank.

Remember, for a standard water heater the temperature should be set at 120 degrees Fahrenheit. You could try flushing the T&P valve to make sure it didn’t become filled with sediment.

And it’s a good idea to test the T&P valve at least once a year to make sure it’s operating properly.

Simply place a bucket beneath the discharge tube. You just want to flip open the relief valve and let it run for about five seconds to make sure it opens fully. Stand back and don’t do this if you’re barefoot or wearing open-toed shoes or sandals. If that hot water splashes out, you could be burned.

Remember, the T&P valve is the only thing that prevents your water heater from becoming a bomb. Once the valve snaps back, make sure it doesn’t leak.

If it does, you’ll need to replace the valve. Next, check to make sure the expansion tank above the water heater hasn’t failed. You can do this by removing the cap. It’s located on top of the tank and press in the Schrader valve. This is the same type of air valve that you’ll find on tires. To see if air or water comes out of it. If water is expelled from the valve, then the tank needs to be replaced.

I hope this is helpful and you have a better understanding of the temperature and pressure relief valve on your water heater.