Water Pouring Out of Pressure Relief Valve: What to Do If Your Heater’s Leaking

If you have a water heater, there’s a chance that you’ve seen or heard water pouring out of the pressure relief valve. This can be alarming, but it’s actually a normal part of your water heater’s operation.

The pressure relief valve is designed to open when the internal pressure of the tank gets too high. This prevents the tank from rupturing and causing serious damage or injury.

It can be alarming to see water pouring out of your pressure relief valve. The good news is that this is usually a sign that your heater is working properly and preventing itself from becoming overloaded with too much pressure.

When the valve opens, water will start to pour out. This is normal and nothing to be concerned about. The best thing to do is to let the water run until the pressure in the tank has normalized.

However, if you’re unsure about what to do or if the water continues to pour out, it’s always best to call a professional for help. In the meantime, here are some tips on what to do if your heater is leaking.

How Does a Water Heater Pressure Relief Valve Work?

A water heater pressure relief valve is a one-way pipe that is designed to release excess pressure and temperature from a water heater when needed. When the internal temperature of the water heater increases to a certain point, the relief valve opens in order to expel hot water and steam from the water heater, thus preventing it from overheating.

On a micro-level, the functioning of this valve works as follows: when the pressure and/or temperature within the water heater surpasses 150 psi and/or 210 degrees, respectively, the valve is triggered and opens, allowing the steam and hot water to escape from the normally closed system.

This then relieves the excess pressure, allowing the temperature to return to a safe and stable level. Additionally, the pressure relief valve prevents water leaks and keeps the water pressure from becoming too low. It is typically located on the top or side of the appliance and has an upward-pointing discharge tube.

What are the reasons why the pressure-relief valve of a water heater leaks?

1. Mineral Deposits

Mineral deposits are small, hard deposits formed by the buildup of minerals, such as calcium and magnesium, in your water supply. These deposits accumulate in the valve body of your water heater, reducing the flow of water and leading to lower-than-intended water pressure.

If left unchecked, mineral deposits can completely clog the spring of a temperature or pressure relief valve, causing it to fail to open when it should. This can be dangerous, as excess pressure and temperature can build up and cause the water heater to malfunction.

In order to reduce the risk of mineral deposit buildup and related problems, it is important to inspect the anode rod of your water heater at least once every two years, and replace it if need be. This will help to draw rust away from the tank, and it is important to use a water softener if necessary.

Taking these steps will help to ensure that your water heater is functioning properly and safely and that you are not at risk of a leaking water heater.

2. Rust

Rust can accumulate in the pressure-relief valve of a water heater due to corrosion of the pipes or valves, the interior rust corrosion caused by water interacting with the steel tank of the heater, and leaking from the anode rod. The anode rod helps to draw rust away from the tank, but eventually, it will deteriorate over time, leading to rust accumulation in the pressure-relief valve.

To prevent this problem, it is important to inspect the anode rod at least every two years and replace it once every 4-5 years, or sooner if you have a water softener. If water damage or a leak is suspected, it is always advisable to contact an experienced professional in order to address the problem before it gets worse.

3. High water temperature and pressure

The causes of high water temperature and pressure that can cause a water heater’s pressure-relief valve to leak are excessive heat and thermal expansion. When the water inside the water heater tank heats up, it takes up more space and causes an increase in pressure.

If the pressure gets too high, the pressure-relief valve will open to release the pressure and allow water to drain out of the tank. Cold water is then added to the tank in order to lower the temperature and pressure inside.

This can happen if the water temperature is set too high, the pressure is too high, or the pressure-relief valve itself is not functioning properly.

4. Leaking Temperature Control Valve

A leaking temperature control valve can cause water to pour out of the water heater pressure relief valve if the valve is faulty or the temperature or pressure exceeds the valve’s preset limits. When the temperature or pressure gets too high, the valve opens and releases water so as to relieve the pressure.

This is a normal safety feature of the valve, but if it is faulty, it may stay open, allowing for water to continuously drain out, resulting in a leak. Additionally, if the valve is clogged with mineral salts left behind from hot water evaporation, the valve may not be able to open when the temperature or pressure exceeds the preset limits, resulting in an unsafe pressure buildup which may eventually lead to an explosion.

5. Leaking Gas Valve

The pressure-relief valve of a water heater can leak for a number of reasons, such as if the valve isn’t seated properly in the tank’s threaded opening if there is sediment or dirt trapped inside the relief port, if the valve has been triggered to open due to excessive temperature or pressure, or if the valve itself is faulty.

To fix the issue, it is important to shut off the water and gas to the water heater, relieve the pressure from the tank, and replace the valve using Teflon tape. If the problem persists, it may be necessary to take further action.

6. Worn or Damaged Relief Valve

Symptoms of a worn or damaged pressure-relief valve in a water heater include flooding, excessive noises, dirty water, water leaks, and ruptured tanks. Flooding is the most dangerous sign that the pressure-relief valve has gone bad and should be fixed immediately by a professional.

Excessive noises, such as rattling or whistling, indicate that the steam has nowhere to escape and the pressure-relief valve is not working. Dirty water can result from the corrosion of the valve, while water leaks may occur if the valve isn’t able to relieve the pressure from the unit.

Lastly, a ruptured tank can happen if the valve isn’t releasing any steam. A faulty pressure valve can also be the cause of a leak, and this needs to be replaced. A slight leak may occur if the pressure-relief valve has not been opened for a few years and should be opened and closed a few times to see if it will seat itself.

7. Pressure Control Valve Failure

The pressure control valve of a water heater can fail due to a number of different causes. These can include boiler limit control problems, closed hot water systems, gas sidearm heater TP valves, expansion tank defects or problems, and leaks into the heating boiler or water heater.

Boiler limit control problems can occur if the boiler temperatures are excessive, possibly due to an improperly set limit control, lack of contact between the limit switch sensor and its mounting well, or a defective control.

Closed hot water systems can cause periodic discharge of the temperature and pressure relief valve due to thermal expansion. Gas sidearm heater TP valves can also cause an overheating condition at the sensor point of the valve.

Expansion tank defects or problems can cause spillage at the relief valve if the expansion tank or compression tank on a hydronic heating system boiler or on other thermal expansion systems is defective. Finally, leaks into a heating or water heater from a higher-pressure building source can cause recurrent TP valve leaking.

8. Stress Cracks in the Water Heater

Stress cracks in a water heater are thin cracks in the metal of the tank caused by water pressure and temperature changes. When the water heater heats up, it expands, raising pressure inside the tank. Over time, the constant expansion and contraction can cause the metal to fatigue, resulting in small cracks along the seam of the tank.

These stress cracks can lead to increased pressure, causing the pressure-relief valve to leak. Pressure-relief valves are designed to release water when the pressure increases beyond a safe level. If the pressure builds up more quickly than normal, the valve may be unable to handle it, leading to a leak.

Testing the valve periodically for proper functioning can prevent this from happening. If the valve is corroded or if water is pouring out of it, it should be replaced. Setting the water heater’s temperature to 120-125° F can also help reduce the pressure and minimize the chances of the tank cracking.

How to fix a leaking water heater pressure relief valve

Fixing a leaking water heater pressure relief valve is relatively simple, and can be completed in a few steps.

Turn off the gas or power to the water heater, as well as the cold-water valve to the water heater. Then, relieve the pressure from the tank by opening the valve located near the bottom of the tank to drain the water a little.

After this, remove the overflow pipe connected to the pressure relief valve and use a pipe wrench to unscrew the leaking valve. Once this is done, use Teflon tape to wrap it around the threads of the replacement valve, and screw it tightly into place.

Reconnect the overflow pipe and open the cold-water cut-off valve. Check for leaks and reassemble the system until no water is leaking from the joints. Finally, turn on the power or the gas, and enjoy your water heater without the valve releasing water.

If you do this step and the temperature-pressure relief valve is still leaking, you may need to carry out a test, so ensure you are wearing closed-toed shoes to avoid scalding. Identify where the relief valve shut off is, check the discharge tube to make sure it is attached firmly and put a bucket under the discharge tube.

Here is a video guide to help you:

Why is my pressure relief valve still leaking after replacement?

The cause of your pressure relief valve still leaking after the replacement could be due to two primary reasons. One, the valve may not be seated properly in the tank’s threaded opening. Two, there may be sediment or dirt trapped inside the relief port.

In either case, the valve needs to be shut off, allowed to cool completely, and then rethreaded or pulled back to clean the port respectively. Additionally, the valve might be leaking because it has not been opened in a few years and has become faulty from lack of use.

Finally, the water heater could have been repaired with a valve from a boiler that is set to go off at a lower psi, thus leading to leaks shortly after installation.

Wrapping up: What Should I Do If water is pouring out of the pressure relief valve?

If water is pouring out of the pressure relief valve of a water heater, it is important to take the following steps:

  1. Turn off the power to the heater. If it is an electric heater, you can flip the breaker. If it is a gas heater, turn off the gas. If there is an on/off switch present on the heater itself, use that.
  2. Turn off the water. Locate the water supply going into the tank and shut it off to prevent more water from building up.
  3. Contact a professional plumber. Damaged or failing water heater pressure relief valves could cause serious damage, so you should contact a professional to repair or replace your water heater, as necessary.
  4. Test the pressure relief valve. To do this, you can use a pressure gauge to check the pressure levels within the tank. If the pressure exceeds 150 psi, or 210 degrees Fahrenheit, then it is time to replace the valve.
  5. If you notice excessive drainage coming from the valve, water flooding, or whistling and screeching sounds, you should take additional steps to protect your water heater and contact a plumber for help.


What is a pressure-relief valve on a water heater?

A pressure-relief valve on a water heater is a safety component that helps to regulate the pressure and temperature inside the appliance. When the pressure and/or temperature inside the water heater gets too high, the valve will open to let out excess hot water and steam, thus helping to prevent the water heater from overheating. The valve is typically located on the top or side of the appliance.

How often should the pressure-relief valve be checked?

The pressure relief valve should be checked annually, by testing it by lifting the handle and releasing pressure from the water heater tank. In industrial refrigeration, the current recommendation is to replace the relief valve on a five-year cycle.

Additionally, the relief valve setting(s) should be checked to ensure they are at least 10% or 15-psi, whichever is greater, above the maximum operating pressure. If unstable process conditions exist, this differential should be at least 10% above the maximum operating pressure or 25 psi, whichever is greater.

Why Is My Water Heater Pressure Relief Valve Leaking?

A water heater pressure relief valve leaking can be a sign of potential danger, as it indicates that excessive temperature or pressure is building up in the tank. This is caused by cold water being heated up, which causes it to expand, thus creating extra pressure.

The pressure relief valve is designed to release this pressure, but if it is unable to do so, it can start leaking. It is important to inspect the valve periodically to make sure it is functioning properly, and if it is found to be faulty, it is best to replace it. In addition, you should install an expansion tank to control the extra pressure that could build up. If the problem persists, you should contact a licensed plumber for help.

What Is The Temperature Pressure Relief Valve (TPR)

The Temperature Pressure Relief Valve (TPR) is a specialized valve installed on water heaters to ensure safety and prevent serious damage or injury. The TPR valve works by releasing water if the pressure in the water heater becomes too high. This happens because heated water expands and can become dangerous if it’s not properly regulated.

The TPR valve releases water if the temperature or pressure in the tank is too high. The valve will open when it senses an excessive amount of pressure or heat, stopping the tank from becoming a potential hazard. It also releases water if the thermostats and temperature control malfunction.

Without a functioning pressure relief valve, water heaters can shoot into the air like a missile. It is important to regularly check and test your TPR valve to make sure it is properly functioning and not leaking. If any issues are suspected, it is best to call a professional for help.

How much water should come out of the pressure relief valve?

The pressure relief valve on a water heater is designed to release water when the pressure reaches 150 PSI or the temperature reaches 210° Fahrenheit. Generally, the amount of water that is released by the relief valve should be between 2 and 20%. If the pressure or temperature exceeds these levels, the relief valve will release water until the pressure or temperature is back within the normal range.

Is it normal for the water heater pressure relief valve to drip?

Yes, it is normal for water heater pressure relief valves to drip occasionally. This is usually due to extra pressure building up within the water heater tank and the valve releasing some of that pressure. The drip is a sign that the valve is working properly and nothing is wrong with the system. However, if the valve is dripping constantly or if you hear or see water and gas escaping, then you should call a professional to inspect and possibly replace the valve.




Hi Guys, Mike is a Mechanical Engineer who specializes in Heating, Ventilation, and Air-conditioning. His love for humanity and his profession propels him to share useful and factual Information on this blog.

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