5 Reasons Water Heater Pop-Off Valve Keeps Popping + Fixes

Pop-off valves are designed to reduce the pressure in hot water heater units. However, it becomes problematic when the valves keep popping off repeatedly.

If your hot water heater’s pop-off valves just won’t stop popping off no matter what you do, it may be because:

  1. There’s no expansion tank connected to the water heater
  2. The incoming water pressure is too high
  3. The pressure relief valve setting is too low
  4. You’ve used the wrong size valve.

This article will explore why your water heater’s pop-off valve keeps popping in more depth and explain how you can fix it yourself with ease.

How Do Pop-Off Valves Work? 

Let’s start with the basics: Water expands when heated. For example, a 40-gallon water heater tank can expand by half a gallon at high temperatures. This expansion increases the internal pressure within the tank. 

Most residential water heaters can withstand up to 150 PSI of pressure at 210 degrees. But what happens when the internal pressure is above the limit? That’s where the pop-off valve comes in, a small switch fixed to the side of a water heater unit that opens up to discharge excess water and reduces the pressure within the tank.

water heater valve repair

Reasons Why Pop-Off Valves Keep Popping Open 

As mentioned earlier, it’s alright for your pop valve to open under too much pressure. However, the valve shouldn’t be popping open when the water temperature and pressure are far below the limit. Below, we list some reasons why that might be happening anyway:

You Don’t Have an Expansion Tank

The expansion tank is a small container often positioned above water heater units. Think of the expansion tank as a reservoir. It stores excess water and reduces the strain on pop-off valves. Without this extra tank, the pop-off valve will continually open and spill water.

expansion tank

Incoming Water Pressure Is Too High

Sometimes, the city’s water supply causes this issue. Normal water pressure should not exceed 80psi. High incoming water pressure will boost the internal pressure in the tank and push the pop-off valve open. 

If this is the case, investing in a pressure-reducing valve is best to control the pressure level. 

You Installed the Wrong Size Replacement

Does a water heater pop-off valve’s size matter? As a DIYer, purchasing just any ol’ pressure valve is a recipe for disaster because there’s no one-size-fits-all water heater pressure relief valve. These gadgets come with different BTU and PSI ratings. 

Even a slight difference can cause problems for your unit. So don’t buy a 120 psi pop-off valve for a water heater with a MAWP rating of 150 psi. Always select a valve with a PSI rating of 150.

Take precautions when fixing or replacing these valves. For example, an incorrect installation can induce explosions or fire outbreaks. Consider contacting a licensed plumber to help out with these risky tasks. 

When Should I Change my Water Heater Pop-Off Valve? 

A functional pop-off valve must withstand at least 125 to 150 PSI. You should always replace the pop-off valve when it no longer performs properly. You should also change the unit after eight to ten years of use to avoid age-related problems.

In addition, pay attention to the valve if you live in a dry region. Consider the incoming water pressure, as high water pressure will degrade the efficiency of the valve.

Although repairing the valve is an admirable goal, replacing the valve is a safer bet than repairing it.

checking tank pressure

How to Change Pop-Off Valve on Hot Water Heater 

It’s time for a replacement. This may be unfamiliar territory. Before purchasing a replacement at the hardware store, take a pen and jot down the used valve’s specifics (BTU and PSI ratings). Better still, bring it along with you.

Find a replacement that matches the specifications of the old one. You should also get an adjustable wrench, garden hose, Teflon tape, and screwdriver. These tools will make your DIY repairs less stressful.

Next, follow the instructions listed below:

  1. Unplug the electric water heater from the main power switch. Shut off the gas valve if it’s a gas water heater. Remember to set the gas valve to pilot or vacation settings. 
  2. Switch off the cold water inlet valve before proceeding.
  3. Before removing the old pop-off valve, ensure the water level is below the valve. Here’s how to check: Open the switch on the pressure valve and watch for water spills. 
  4. Drain the heated water if the water level is too high. Connect a garden hose to the drain stopper. Next, open the hot water side of your bathroom or kitchen water faucet to let air into the hot water tank and reduce pressure. 

You can also use this opportunity to flush your water heater. 

  1. Use a screwdriver to open the drain valve for a few minutes until the water level falls below the position of the pressure valve. 
  2. Is the water level below the pop-off valve position? If not, keep the drain valve open for a few more minutes before removing the pressure valve. 
  3. Unscrew the drain pipe connected to the pop-off valve. 
  4. Next, use the adjustable wrench to grip the valve and rotate it counterclockwise. 
  5. Bring out the replacement and check if the ratings are similar to the defective valve. 
  6. Next, wrap a Teflon tape around the base of the thread of the new valve. Ensure the tape does not cover the top of the thread since you don’t want pieces of tape in your water heater. 
  7. Then, use an adjustable wrench to fix and tighten it into the water heater. 
  8. Re-attach the drain pipe to the valve, and open the cold water valve. Next, open the gas valve and set it to the desired temperature. 


Always fix the issue promptly to avoid unnecessary damage to your water heater unit. You may also consult your building code if the problem reoccurs. And always take all the precautions you can to prevent burns, fires, and other injuries or damages.