Is Your Water Heater’s TPR Valve Leaking? Here’s What to Do

Updated: Jul. 01, 2024

The TPR valve is a critical safety feature on water heater tanks. A leak could indicate high pressure or a malfunction that requires replacement.

“Without a TPR valve, a water heater would be like a giant bomb in your house. In the early days of water heaters, before TPR valves existed, there were cases where the water heater would explode.” This warning comes from master plumber Robert Mazzacone, and if it doesn’t grab your attention, it should.

A malfunctioning TPR valve is as dangerous as one that isn’t there, and if you haven’t checked the one on your water heater recently, you really have no idea whether it’s working properly or not.

Water from your faucet that’s hot enough to scald you and unusually high water pressure are two signs of dangerous conditions in your water heater tank. If the TPR valve isn’t working, you’re courting disaster — maybe not an actual explosion, but definitely the possibility of a tank rupture.

Here’s how to check your TPR valve and, if necessary, replace it.

What Is a TPR Valve?

“The Temperature and Pressure Relief (TPR) valve on your water heater is a critical safety feature designed to release water if the temperature or pressure inside the tank gets too high,” explains Calgary plumber Asif Bux.

The TPR valve is a spring-loaded, brass valve located on the top of the tank or on the side near the top. If it has been installed according to code, it’s connected to a discharge pipe that runs along the side of the tank and terminates six inches above the floor. However, many TPR valves have been installed incorrectly and lack this pipe. Whether installed correctly or not, the TPR valve is there for one reason: to maintain the pressure inside the tank at a safe level.

How Does a TPR Valve Work?

A TPR valve is very simple: It’s in a cylindrical brass housing about four inches long with a 3/4-inch inlet and a perpendicular 3/4-inch outlet. The inlet is screwed directly into the tank, and the valve has an internal spring-loaded flapper designed to open when the tank pressure exceeds its preset limit. On the top of the housing is a metal lever that allows a homeowner or plumber to test it by manually opening it.

When the tank’s internal pressure exceeds its limit, the TPR valve opens, allowing steam and hot water to spray from the outlet until the tank pressure drops below the limit. If the valve has no discharge tube, the spray could injure anyone standing nearby, which is why the plumbing code requires the tube. It screws into the outlet and directs outflow directly at the floor, where it can’t hurt anyone.

How to Tell if Your TPR Valve Leaks

“If your TPR valve is leaking, it indicates that it is doing its job, but it also signals a potential issue that needs to be addressed,” says Bux. While a leaking TPR valve isn’t as dangerous as one that won’t open, it could well be a warning of dangerously high pressure in the tank. Here are some signs of a leaking valve:

  • Water on the floor under the discharge tube.
  • Water is dripping from the valve outlet. You’ll only see this if there’s no discharge tube.
  • Water seeps around the connection between the valve and the tank.

If you see signs of a leak, the first thing to do, according to Mazzacone, is to check the home’s water pressure. You can do this by screwing a pressure gauge onto an outdoor faucet or one in the laundry room and opening the faucet all the way. If the pressure is above residential limits (usually from 60 to 80 psi), you may need to adjust the pressure-reducing valve (PRV) located near the water meter to lower it.

A valve will also leak if the tank water temperature is too high, and this is probably true if the water from the faucets is too hot to touch. Adjust the temperature control on the front of the tank to 120 to 140 degrees F to see if that stops the leak.

How to Replace a TPR Valve

Before assuming the valve needs to be replaced, Bux recommends testing it. Use the lever to manually open the valve and let water spray out (take appropriate safety precautions if there’s no discharge tube), then release the lever. Sometimes, debris lodges in the valve, preventing it from closing, and this should clear it out.

If the valve continues to leak, Mazzacone advises checking the expansion tank. “We often find that expansion tanks are either not installed to code or missing entirely, requiring installation or replacement to solve the issue.”

Whether or not the expansion tank is working properly, if your TPR valve is leaking, it should be replaced. Here’s how Bux does this simple procedure:

  1. Let the water cool: Turn off the gas or electricity and let the tank’s water cool to a safe temperature.
  2. Drain the tank: Drain a few gallons of water from the tank to lower the water level below the TPR valve. Use the drain valve at the bottom of the tank and a garden hose to direct the water to a safe location.
  3. Remove the old valve: Use a wrench to unscrew the old TPR valve. Be cautious, as the valve might be corroded or tight.
  4. Install the new valve: Wrap plumbing tape around the threads of the new TPR valve and screw it into place. Ensure it is securely tightened, but avoid over-tightening.
  5. Restore power and water: Turn the water supply back on and restore power or gas to the water heater. Check for leaks around the new TPR valve.


What If your TPR valve Is stuck?

You should test your TPR valve every six to 12 months or so by opening the lever and ensuring water sprays out. If nothing happens, the internal mechanism is probably stuck. In this case, immediately turn off the gas or electricity and replace the valve when the water cools.

What’s the difference between a TPR valve and a drain valve?

All water heater tanks have both valves. The TPR valve is at the top and opens automatically to release steam and lower pressure. The drain valve is at the bottom, and you open it manually to allow water out of the tank.

Do tankless water heaters have a TPR valve?

No. Tankless (on-demand) water heaters have no tank, so they don’t need a TPR valve to release pressure. They don’t have a drain valve, either.

About the Experts

  • Robert Mazzacone is a third-generation licensed master plumber and owner of Mazzacone Plumbing & Heating, based in Westchester County, NY.
  • Asif Bux is the service manager of Comfort Union, a plumbing, electrical and HVAC company located in Calgary, AB.