What Causes A Water Heater Relief Valve To Open?

What’s Going on Inside the Water Heater

Temperature and Pressure – Hand in Hand

Temperature and pressure go hand in hand in a confined space like a tank. Raise the temperature and the pressure rises. Raise the pressure and the temperature rises. It’s all physics. The key is to control them.

The Relief Valve – A Mechanical Backup

So, What Could Be Wrong if the Relief Valve is Opening?

Several possible problems may cause a water heater relief valve to open. Each should be investigated thoroughly and fixed. If the relief valve is opening and closing, or if it leaks by, something is amiss with the control systems on the water heater or with the valve itself.

Check the Thermostat Settings

Those Noises in the Water Heater Tank

Checking your Relief Valve

Any mechanical device is subject to failure over time. A mechanical relief valve is no different. If your relief valve begins to open regularly and everything else is operating normally, you should suspect a bad valve.

Before you jump in and replace the valve, you should check the operation. Operating the relief valve may solve the problem by breaking up the scale built up in the valve. Manually checking the relief valve is not difficult

Step 1 – Get Prepared

Gather the things you will need to do the relief valve test.

Step 2 – Get Everything in Position

Place the bucket under the discharge tube on the relief valve. If the relief valve empties into a drain or outside, you don’t need the bucket. If the drain is next to the water heater, stuffing a few rags around the opening will help prevent splashing hot water when the valve opens.

Step 3 – Open the Valve – Carefully

Replacing A Bad Relief Valve

Replacing a faulty water heater relief valve is well within the scope of most home DIY’ers. Following the proper steps can have your water heater up and operating normally with ease.

Step 1 – Do the Job Safely

Before you do anything, turn off the fuel or electricity to the water heater. Close the gas valve or open the breaker at the service panel. Turning things off prevents accidents that could injure you or damage your water heater.

Step 2 – Get the Parts and the Tools

You will need to assemble all the parts and the tools before you start. Having everything you need will make the job go much quicker and with less frustration.

Step 3 – Open the Relief Valve Carefully

Remember that the water in the tank may still be under pressure and can be hot. If your drain line doesn’t run to a drain or outside, put a bucket under the tube. Slowly open the relief valve and let it run until the water flow stops.

Step 4 – Remove the Drain Line

If your relief valve has a drain line, unscrew it from the relief valve. In some cases, this may require that you cut the drain line. You should be prepared with the proper fittings and materials to repair the drain line.

Step 5 – Remove the Relief Valve

Using the crescent wrench, carefully remove the relief valve from the water heater tank. If the relief valve has mineral buildup or corrosion, it may take some effort to get the valve to turn.

Step 6 – Clean the Threads on the Tank

A small wire brush is a useful tool for cleaning the threads on the opening where the relief valve enters the tank. There may be scale buildup, corrosion, or Teflon plumbers tape still in the threads. Make sure the threads are clean and free of debris.

Step 7 – Install the New Valve

Apply Teflon plumbers tape to the new valve threads. Apply the Teflon tape in the same direction as the threads. On most valves, this is clockwise.direction. Carefully thread the new valve into the opening on the tank. Use the crescent wrench to tighten the valve into position.

Step 8 – Replace the Drain Line

Repair or replace the drain line on the relief valve. Don’t forget to apply Teflon tape to any threaded joints. If you had to cut the drain line, make those repairs as needed.

Step 9 – Turn on the Water Supply

Turn on the cold water supply to the water heater. Give the water heater tank time to refill and check your work for leaks. If you spot leaks, go back, and redo the installation and make sure the Teflon tape is properly applied.

Step 10 – Return your Water Heater to Operation

If you don’t have any leaks, it is time to get things back to normal. With the cold water supply on, relight the pilot light if necessary. If your water heater has an ignitor, follow the directions on the water heater to reset the control valves. If the water heater is electric, turn the breaker on at the service panel.

Step 11- Wait and Check Again

Give the water heater time to bring the water in the tank back to the operating temperature. Make sure the thermostat is set properly at 120 degrees Fahrenheit. Once the water temperature is up, check the fittings for leaks. It is also a good idea to operate the relief valve a few times to ensure it is operating properly.

When the Relief Valve Operates, Investigate

A relief valve that is operating on a water heater is a sign of something wrong. The water heater needs examination and the problem diagnosed. A quick repair or adjustment can prevent major problems further down the road. We hope that this article gives you the insight to diagnose and fix any problem with your water heater.