What causes a water heater's relief valve to drain water? (2023)

So you got some stuff out of your basement only to find it's flooded with water.

The first thing that comes to mind is the kettle.It drips out of the relief valve again.

But why does the relief water drain water in the first place?

If a water heater's outlet valve is leaking, it could be either too high a temperature, too high a pressure, or just a leak in the relief valve itself. At temperature and pressure, the relief valve does its job and prevents an explosion. But you may want to have the pressure valve repaired if it is leaking.

Reasons why a heater's relief valve drains water

Most standard indoor water heaters have a relief valve. This purpose of the relief valve is to drain water in two cases:

1. Excessive water temperature
2. Water pressure too high

If either of these events occurs, the relief valve will activate and excess hot water will flow out of the relief valve.

But that's not always the case. Sometimes there is a third reason why water is leaking from the relief valve and that is if your relief valve is defective or not properly sealed. In this case you have to replace the relief valve completely,

Here are some of the ways you can test what is causing the relief valve to drain water:

Diagnosing the cause of leaks in the relief valve

As we have already mentioned, there can be three reasons for this. Here are easy ways you can test it:

1. Excessive temperature

Check the temperature with a thermometer

The very first test you should do is the water temperature. To do this, simply leave the heating running and turn on a hot water tap anywhere in the house for a good 2 to 3 minutes.

Then hold a thermometer in the running water for 10 to 20 seconds and read the temperature. If your water temperature is 210°F or higher, it is likely that your relief valve is draining water due to water overheating.

However, if the water temperature is below 210°F, there is likely a problem with the water pressure or the relief valve itself.

2. Excessive pressure

With a water pressure gauge

Using a water pressure gauge is an easy way to determine if excessive pressure is causing the relief valve to release water.

To do this, simply go to your local plumbing store and purchase a threaded pressure gauge. These are usually accurate enough for our purposes here.

Once you have the pressure gauge, simply attach it to a hose bib around the house. The cold or hot water faucet in the laundry room is a good place to start.

Normal water pressure is between 40-80 PSI when no other faucets are running. Check the reading again by attaching the pressure gauge to another piece of hose and testing the water pressure there.

If the pressure is less than 80 PSI, all is well and good. But if it's more than 80 PSI then you have a problem.

Check for intermittent pressure rise

Here is another scenario:

If your water pressure is closer to 80 PSI, your relief valve can still dispense water. If so, your water system could be suffering from an intermittent or periodic pressure surge.

How do you diagnose this problem? Drain your heater's hot water supply by running all hot water when you shower or bathe, or simply open all of the hot water valves in your home to drain the hot water.

After the water has gone cold, close all taps and wait for the heater to heat the cold water again. Run the water again and check the reading on the pressure gauge. If it's still between 40-80 PSI, the pressure isn't the issue here.

3. Defective heater pressure relief valve

Faulty relief valve

If the problem is not related to your water temperature or pressure, you may have a faulty relief valve. Sometimes the relief valve is not installed properly, or the gasket or other parts fail over time, causing the relief valve to drip.

Both at too high a pressure and at too high a temperature, the relief valve tends to release water in large quantities. If the fault is with your relief valve, it is probably dripping slowly and gradually not from the relief valve but from its connection to the heater.

Wrong relief valve

Another possibility is that you installed the wrong valve. A standard water heater temperature and pressure relief valve (TPRV) delivers water at 150 PSI or 210°F.

If you accidentally installed a boiler relief valve or other valve, it will trip at a lower pressure and drip under the wrong conditions.

Fastening of the pressure relief valve of a heater

How you repair your water heater's relief valve depends on what is causing the problem that is causing the leak. A few tools from your local hardware store and warehouse may be all you need to fix the problem.

However, if the problem is beyond your understanding and you are unfamiliar with plumbing, you will need to contact a plumber to get the job done.

Fixed water temperature issues

When the relief valve isdrain waterB. due to too high temperature, then the relief valve itself works as it should and does not need to be replaced.

You can try lowering the temperature or contact a plumber for the solution if the relief valve is draining water too frequently.

Fixed water pressure issues

There is no single solution to excessive water pressure. If the pressure increase is constant, as in the first pressure test, you must install a new pressure reducer.

Pressure reducers are easy to find in most hardware stores and with a little expertise you can also install them yourself. Otherwise, you could just call your plumber to fix it for you.

However, if you have intermittent pressure increases, the best solution would be to install an expansion tank. Here's the science behind an expansion tank. When the heater starts heating water after some hot water runs out, some excess hot water flows back into the main inlet pipe as it expands, causing water pressure in the pipes to rise as it has nowhere to go.

An expansion tank provides a port of call for the excess hot water returning to the supply line, preventing the pressure from rising too high and allowing water to escape through the relief valve.

Fixed issues with relief valves

After some time heatingpressure relief valvescorrode or leak due to a faulty seal. In this case, you can quickly get a new relief valve from the local hardware store and replace it yourself with just a few tools.

When doing this, make sure that the new relief valve you purchase is compatible with your water heater and is rated for 150 PSI and 210°F. If you are hesitant to replace the valve yourself, you can have your plumber fix it.

FAQs

Is a Leaking Relief Valve Dangerous?

If your T&P relief valve is leaking, it means something is wrong with it. Replacing a T&P valve usually doesn't take much effort, but if you don't, the valve could potentially clog and cause an explosion.

Why does the relief valve overflow when draining water?

If the water temperature exceeds the limit, aKettleusually dispenses a lot of hot water to lower the temperature. However, an overflow can also be caused by a defective or leaking valve.

Why does my expansion tank keep filling up with water?

In the event of excess pressure in the heating system and insufficient air in the expansion tank, the water is pushed back into the expansion tank instead of into the main water supply line.

How can you tell if your pressure relief valve is defective?

If you notice signs such as reduced pressure in the heater, high or no water pressure, or even vibration noise from the plumbing, the valve is likely defective.

How to fix a leaking temperature and pressure relief valve?

A T&P relief valve is a quick fix and easily replaceable by most DIYers. Just get a new one from your local hardware store for a few bucks to make your heater new again.