Water Heater Pressure Relief Valve : 5 Things You Should Know

If you’ve been having issues with your water heater recently, you might find that you’re paying high energy bills, not getting access to hot water when you want it, or your water pressure is low.

This can be frustrating, but what’s the cause? You might be having a problem with the water heater pressure relief valve.

Fortunately, by understanding how relief valves work, you can solve whatever problem you’re having with the one on your water heater. In this article, we’ll review everything you should know about this valve.

Finally, you can get hot water at the right pressure again, enjoying your morning shower like you used to. Read on to learn more.

water heater pressure relief valve
water heater pressure relief valve

What Is a Water Heater Pressure Relief Valve?

A water heater pressure relief valve, also referred to as a T&P valve, pressure relief valve, or water heater temperature valve is a safety feature that you can find on any water heater. The reason it’s there is to keep you safe in case the water pressure is too high.

Without this safety feature, your water heater could end up breaking. You could potentially end up with burns if the high water pressure is dangerously high.

This valve also ensures that there aren’t any leaks in your water heater, which would lead to low water pressure when you want to use it to wash the dishes or take a shower.

How Does a Water Heater Pressure Relief Valve Work?

The water heater pressure relief valve is in place so that it can relieve excess pressure and temperature in a water heater if either of these is too high. Because this everyday appliance is a closed system, thermal expansion occurs in water heaters.

Here’s how it works. Whether your water heater is heated by electric elements or a gas burner, both the metal tank and the water inside expand when the hot water temperature is somewhere between 120 and 140 degrees.

It’s totally normal for the water and water heater to expand to a certain extend. After all, this is what naturally happens when the temperature rises.

However, when the temperature is 210 degrees—or the pressure is 150 pounds per inch (psi)—this is far too much pressure and heat in the water heater. If it’s the case, you should change your hot water heater temperature.

If your water heater pressure relief valve is working, this is when it will open. This releases steam and hot water from the discharge tube, making your water heater operate safely again.

On the Micro-Level

On the micro-level, the functioning of this valve works like this. The relief valve itself has been set up by a professional or pre-designed to open when the temperature or pressure reaches a dangerous level.

When functioning properly, it will open as it’s designed to when the levels of heat or pressure are high. The liquid comes out through this auxiliary route, relieving the heat and pressure within the water tank.

The rising of heat and pressure stops. Once the temperature and pressure returned to safe levels, the water heather pressure relief valve closes.

This specific state that the water heater is in is called the “blowdown.” Usually, the “blowdown” is defined by professionals (and is used in the design or set up of the valve) as a specific pressure percentage.

The “blowdown” is usually somewhere between 2 and 20%. Once the pressure has reached the “blowdown” amount, the pressure relief valve will close again so that you can use the water heater as intended.

Where Is the Water Heater Pressure Relief Valve?

If you’ve been noticing any issues with your water heater pressure relief valve, then you need to know where it is on your water heater. Usually, you can find it on the top or side of this appliance. It’s a valve that’s connected to a plastic or metal discharge tube that points up.

The water heater pressure is already installed when you receive your water heater (or buy a home that has one already). It’s actually welded onto the tank; you’ll see a threaded inlet where it is.

You can’t replace or remove it. The valve itself has been screwed into the threaded inlet.

This is for safety reasons. Everything has been done according to standards that have been mandated by plumbing codes. So if you’re having any issues with the valve, you’ll have to call a professional to have it fixed.

This said, if you’re only having issues with the discharge tube, this is easy to replace. You won’t have to drain or power down your water heater, and you can deal with it yourself.

This said, considering that there might be other issues causing discharge tube problems—issues connected to high water pressure or temperature—it’s safest to have a professional deal with this too.

Testing Relief Valves

If you suspect there’s a problem with your water heater pressure relief valve, you can do a test. This is actually good idea if you don’t have any problems at all, as this type of maintenance will protect your water heater—and yourself.

Remember before you do the testing to change into closed-toed shoes so that you can avoid scalding.

To get started, identify where the relief valve shut off is. Usually, you can find it upon the cold water feed, which is on top of the water tank, on the right side where the inlet is.

Once you’ve done this, take a look at the discharge tube to make sure that it’s attached firmly. Then, take a bucket and put it under the discharge tube.

Now, pull the metal lever of the valve slightly, so that a small amount of the water—a quarter cup or so—discharges into the bucket.

Finally, release the level so that it quickly snaps into the original position. If it doesn’t snap quickly into this original position, then your water heater valve isn’t working and needs to be replaced.

Fixing Your Water Heater Pressure Relief Valve

When your water heater pressure relief valve isn’t functioning properly, it’s usually for one of to two reasons. It either sticks so that it doesn’t properly open or close, or it has a leak, which means that it’s continually dripping, lowering your water pressure.

Fixing a Sticky Valve

If your valve is sticky, then it becomes stuck in a closed (downward) or open (extended position). If it’s closed, then the valve won’t be able to relieve the heat or pressure that builds up in the closed water heater system. There could be a rupture as a result.

If it’s open, on the other hand, then it will continuously leak water, which could end up flooding your home.

Sometimes, you can easily fix this problem by opening and closing the valve lever a few times. However, if it continues to stick, then you’ll need to replace it.

Fixing a Pressure Relief Valve Leaking

Your water heater is leaking? Make sure that it doesn’t come from the valve before replacing it. If your pressure relief valve is leaking, then this maybe because it isn’t seated properly in the tank’s threaded opening. This is quite a common issue if you’ve recently replaced your old valve with a new one. To fix this issue with this cause, you have to take several steps.

First, shut off your water heater. Wait for it to cool completely. Then, remove the valve and rethread it into the water tank opening.

Another reason the valve could be leaking is that there is sediment or dirt trapped inside the relief port.

To fix the leaks in valves issue, pull back the metal spring valve lever, after which you’ll discharge water that falls into the bucket.

If the lever snaps into its original position and it’s still leaking, you need to turn off the gas valve by turning it to the off position. Then, shut the water off so you can replace the valve safely.

A Note on Safety

If a water pressure issue is what is causing the water heater pressure relief valve to not work, then it might be dangerous for you to change the valve yourself. Generally speaking, it’s a good idea to hire a professional to protect yourself.

Need Your Water Heater Valve Replaced by a Professional?

Now that we’ve reviewed everything you should know about a water heater pressure relief valve you might have realized that you need to replace your water heater valve. However, to be as safe as possible, you want to hire a professional.

Water heater pressure relief valve can leak and break your hot water tank.

7 Comments

  1. Avatar Arie B on July 3, 2021 at 8:59 am

    I don’t see my water heater pressure relief valve. How can I locate it? I tried my owner manual but didn’t saw it.

    • Avatar Well I just put in a new hot water heater and I was just wondering the pressure release valve feels warm is it supposed to on February 27, 2022 at 7:34 pm

      Well I just put in a new hot water heater and I was just wondering the pressure release valve feels warm is it supposed to.. this Michele

  2. Avatar John on January 12, 2022 at 2:17 am

    Located on the side or top of water heater. It should have a pipe attached to it.

  3. Avatar Nelson Truesdale on March 11, 2022 at 5:38 pm

    I replaced the pressure release value 2 times and for some reason it keeps opening and let’s all the hot water out then it closes when the hot water is gone. Like I said I bought 2 new one’s and its still doing the same thing. Please help.

    • Avatar Plumber Mike on May 4, 2022 at 1:34 pm

      Your water pressure could be too high and/or you may have a faulty expansion tank.
      That’s where I’d look first.

    • Avatar Tickerguy on April 10, 2022 at 10:04 pm

      The odds are your thermostat in the water heater is not shutting off when the setpoint is reached. The water will continue to get hotter until the relief valve opens. This is extremely dangerous; if the valve FAILS to open the water heater can explode and the superheated water inside will flash-boil (this can do a number on your house, including potentially launching the tank all the way through the roof!) Check the thermostats (there are two on an electric heater; an upper and lower); they are not terribly expensive but if you’re not comfortable working around electrical items call someone — that’s a 240V appliance and if you don’t have it shut off or manage to short it to the case (and the ground is not well-attached) it can kill you.

  4. Avatar tom kinlaw on May 4, 2022 at 11:22 am

    Does the pipe that connects to relief valve unscrew think thats were leak is, damp on top .
    Like to just replace pipe with black pipe.

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