What is the water heater pressure-relief valve?

Most homeowners aren’t all that familiar with the detailed inner workings of their home appliances. For the most part, your oven, dishwasher, dryer and other appliances all just work. The same thing goes for your water heater. Often tucked away in a garage, closet, or basement, it’s easy to forget about the water heater—despite how important it is to your family’s daily routine.

If there’s one piece of your water heater that you should know, however, it’s the pressure-relief valve. This water heater safety valve is crucial to the safe operation of your water heater. In this article, we’ll go through what this valve is, how exactly it works, and what you need to do when something goes wrong with it.

What is the water heater pressure-relief valve?

Your water heater pressure-relief valve—also known as a T&P valve—is a critically important safety feature of your water heater. In short, this valve helps alleviate excess pressure from within your water heater, helping prevent potential tank bursts and leaks. A T&P valve can be found on every standard water heater and on some tankless water heaters.

As we’ll explore in the sections below, T&P valve problems can pose a risk to both your water heater and your home. If you think you might need T&P valve replacement, you need to call our plumbers right away. You don’t want to procrastinate on water heater problems. At best, your water heater could stop working, leaving you and your family without hot water. At worst, your water heater tank could fail, potentially flooding your home. The stakes here are real.

How does this valve work?

Your water heater warms and then stores heated water inside of its metal tank. Most water heaters store water at between 120 and 140 degrees—this is typically warmer than what’s needed at the tap, but not cool enough to become cold by the time it reaches your shower heads and faucets. At this temperature, the PSI (pounds per square inch) pressure inside your water heater is well within the parameters your water heater was designed to handle.

Problems typically arise when things heat up. Whether due to a change in the temperature setting or due to a malfunction, higher water temperatures mean more pressure inside the tank shell. At about 200 degrees, the water heater is starting to feel the stress of a higher PSI.

This is where the water heater pressure-relief valve comes into play. When the pressure reaches a certain point, it forces the valve open. Your relief valve is connected to a long discharge tube. When the valve opens up, both steam and hot water are forced out of this tube and onto the ground around your water heater.

This continues until enough pressure is released for the valve to close. Plumbers refer to this as “blowdown.” While you’ll have some water on your garage or closet floor that you’ll need to clean up, it’s far better than the alternative. Without a functioning valve, the pressure in the water heater can climb to dangerous levels. Eventually, the tank may “burst,” causing water to flood out of the appliance and into your home.

Testing the relief valve

It’s a good idea to routinely test your pressure-relief valve. As we’ll explain in a section below, T&P valves can malfunction or become “stuck” after years of no usage. You should ensure yours is working so that it can continue to protect your water heater and your home. Most homeowners pair this with an annual water heater flush—this makes it easier to remember this important task.

Luckily, testing your valve doesn’t require increasing the temperature and pressure to unsafe levels. Instead, you’ll need to position a bucket under the discharge pipe. Carefully pull the valve open. If water comes out of the discharge tube and into your bucket, that’s a good thing. Release hold of the valve. Its lever should “snap” back into place and water should stop coming from the tube. This, too, is an indication that your relief valve is working as it should.

Watch: See a T&P valve in action

Watch this video to see what a T&P valve looks like, how it opens to release pressure from the water heater, and what our plumbers need to do in order to replace a faulty valve.

Do I need to replace my T&P valve?

Your relief valve should last as long as your water heater does. However, T&P valves are known to encounter issues that cause them to malfunction. A safely functioning valve relies on its ability to both open (when it detects high pressure) and close (when it detects that the pressure issue has been resolved). If your valve is stuck and can’t do one or both of these things, it needs to be replaced as soon as possible.

Like everything else associated with your water heater, this valve is subjected to the long-term spread of corrosion. This can cause the valve to no longer emit water or steam, or to spring a leak. If you’re noticing dripping water coming from the T&P valve, you have a problem that goes far beyond the small pool of water on the floor. A leaking valve indicates a pressure problem, which means your water heater is going to struggle to keep its water at the right temperature.

When should I call Wagner?

If your pressure-relief valve is either stuck or leaking, you need to call the plumbers here at Wagner. T&P valves were not designed to be replaced by homeowners. In fact, most manufacturers designed these valves to be hard to remove, so that this critical safety feature couldn’t be intentionally disabled. You’ll need our plumbers, with their tools and expertise, to handle the job.

Homeowners here in Albuquerque know and trust our plumbers to do the job right. We’re proud to be your home’s best friend. Generations of homeowners have turned to our team to help them with their plumbing and water heater problems.

We’re ready to help you, too. Contact us today to get one of our plumbers out to your home.

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What is the water heater pressure-relief valve?