This article was written by Mike Morgan, the owner of Morgan Inspection Services. Morgan Inspection Services has been providing home, septic and well inspection services throughout the central Texas area since 2002. He can be reached at 325-998-4663 or at mike@morganinspectionservices.com. No article, or portion thereof, may be reproduced or copied without prior written consent of Mike Morgan.

RPZvalveinstallation

So now you know what a TPR valve is, what it does, why you need one on your water heater, and how to test it to ensure that it is working properly.

NOTE: The terms pressure relief valve, T&P (Temperature & Pressure), TPR (Temperature Pressure Relief), and popoff valve all refer to water heater pressure relief valve and will be used interchangeably in this post.

Although it is not a common occurrence for a water heater to become over-pressurized, so T&P valves do not actuate frequently.

When water changes from a liquid to a vapor (when it changes from water to steam), it expands to many times its original volume. In fact, water will expand and fill a volume about 1600 times its original volume when it changes from a liquid to a vapor.

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Often simply opening and closing the valve a few times will clear the blockage and allow the valve to seat(close) properly and stop leaking.

Water heaters are designed to withstand pressures of at least 150 PSI, so the relief valve is designed to prevent the water heater from rupturing.

The BIG DANGER that you need to be concerned about is that a rupturing water heater can explode and cause serious property damage, injuries and even death

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A water heater temperature pressure relief valve or T&P valve is a safety device required to be installed on all tank-type water heaters. Its purpose is to open briefly and release water from the water heater in order to lower the pressure in the event that the water heater becomes over-pressurized or overheated.

Flooding your home with water may sound bad enough – and if you are lucky, that will be all that happens if your water heater ruptures.

(Keep in mind that some water may continue to drip out of the pipe for a minute or so after the valve is opened just because the interior of the pipe has some water in it, so if you’ve tested it, wait a minute or two to make sure if it is or is not leaking.)

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If you have ever camped in the mountains and cooked or boiled food, then you know that cooking times are different in the mountains than they are at sea level. This is because the atmospheric pressure is lower at higher elevations which makes the boiling temperature of water lower in the mountains, so you have to cook your food longer.

The possibility of an exploding water heater is why we must have a properly functioning relief valve installed on our water heater.

This rapid change in volume can result in a tremendous explosion.   (Watch this video to see a rupturing/exploding water heater.)

Testing the valve without a proper discharge line could allow you to be burned by steam or very hot water. A discharge line will safely direct the hot water and steam away from the valve.

Testing it occasionally to ensure that it is working, and replacing it, if necessary, is a quick and simple thing that you can do to ensure that your water heater does not become a danger to your family.

To test it, simply raise the lever on the relief valve for a few seconds and ensure that you hear and see water flowing freely out of the discharge line on the valve.

Double CheckValveAssembly

WARNING: If there is no discharge line on the T&P valve, do NOT test it until you have had a proper discharge line installed.

Without this relief valve, an over-pressurized water heater could explode causing serious injury, property damage, and even death.

It is a rare event that a water heater ruptures and explodes – because several uncommon circumstances must occur in order for this to happen.

Superheated water is water that has been heated above its normal boiling point (212° F), but because of the higher pressure, the water does not boil, but remains a liquid.

RPZvalve

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A rupturing water heater may not sound so dangerous. All it’s going to do is allow water to run all over and damage flooring and walls. Right?

T&P valves are designed to open if the pressure in the water heater reaches 150 psi, or if the temperature reaches 210 degrees.

If you have noticed some water in the pan under your water heater or have noticed water dripping out of the discharge pipe on your water heater, then your water heater relief valve is likely leaking.

However rare it may be, it is still important to protect against this happening. Fortunately, it is a simple process to ensure that your water heater has a properly-operating relief valve.

Corrosion, mineral deposits, or other buildup in the water heater sometimes get in the way and prevent the valve from closing or seating properly after opening.

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If you do not hear water flowing when you test it, or if you only get a trickle of water, then the valve needs to be replaced.

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When an over-pressurized water heater ruptures, the pressure will immediately drop to atmospheric pressure. This drop in pressure will cause the superheated water, to instantly change from a liquid to a vapor (from water to steam).

Therefore, if you look at your water heater, you should find the relief valve installed into the top of the water heater or in the upper part of the side of the water heater.

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Over the past 145 years, Blackwoods has grown from being a small marine supply business on the banks of Sydney Harbour, to where we are today, Australia’s largest provider of industrial and safety supplies. Today we support businesses, big and small, with our range of over 200,000 products from the world’s best brands. With unrivalled expertise and the ability to bring together the best of the best, we have earned our place as Australia’s first choice for industrial and safety products and services including PPE, welding and gas, power tools, hand tools, workwear and much more. Blackwoods is proud to provide products and services that are essential to the economic growth and prosperity of our country. Everyday we help more people to build a better Australia.

Nevertheless, to increase the safety within our homes, pressure relief valves have been required on water heaters since the 1960’s.