When to Close the Pressure Relief Valve While Draining a Hot Water Tank

Closing the pressure relief valve on a hot water heater.
Closing the pressure relief valve on a hot water heater.

After draining a hot water heater, do you reset the pressure valve before refilling the tank or after? -Desiree’

Hi Desiree’
It’s important to remember to close the pressure relief valve on the hot water heater when you are through draining it. Otherwise, water will run out the valve and through the discharge pipe once it refills.

Since the pressure relief valve vents at the top of the tank, you could wait until the tank is full before closing it, but it’s better to close it when you start refilling the tank in case you forget. Here’s how to go about it.

Once you’ve drained the tank as shown in our video on How to Drain a Water Heater

    1. Open the cold water intake valve for a minute to stir up and drain the last bit of sediment.
    1. Turn the cold water intake valve back off.
    1. Close the outlet valve at the bottom of the tank.
    1. Remove the hose from the outlet valve.
    1. Close the pressure relief valve.
    1. Open the cold water intake valve to refill the tank.
    1. Open a hot water faucet at a sink and allow it to run while refilling to release any air trapped in the tank.
    1. Once the tank is full, close the sink faucet, and check the discharge pipe on the pressure relief valve to be sure it isn’t leaking.
    1. If the valve leaks, see our article on How to Repair a Leaking Pressure Relief Valve.
  1. Once everything is good to go, turn on the electricity or light the gas burner to heat the water in the tank.

Good luck with your project,

Danny

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9 COMMENTS

  1. Thanks for the great tips and instructions(step by step) both written and visual. The videos really help for someone like me who learns better after seeing it done.

  3. What happens if you forget to open the pressure valve when you are draining it and it wasn’t open when you refilled it?

    I replaced 2 elements yesterday and I didn’t do anything with the valve at all.

  4. Thanks for the info. I had a leak with the copper pipe running hot water out. I drained some water to release the pressure. Now that the leak is repaired, I have no hot water. What went wrong?

  5. @John, I’m in the same boat. Yesterday I replaced the upper and lower thermostats, today I’m replacing both elements although the old elements tested good. Confused. We’ll see what happens when I fill this baby up and crank the power. Letting her dry out a bit now, had water all over. It ought to be mandatory that hot water heaters are a foot off the ground! Working with a spigot inches from the floor sucks, then throw a drip pan in the mix, this old man was cussing and I don’t cuss!

  6. I just replaced both thermostats and both elements. This boiler is at our beach house in Sea Isle Galveston and the upper element started leaking from the O-ring. Water got all over the both rusty thermostats. Ordered the kit from Amazon that comes with everything you need, including the O-rings. Disconnected the Power at the switch… Closed the main inlet water valve, drained the water at both bathrooms sinks. Cracked open the bottom drain valve and started draining the tank. Cracked open the upper element till I could hear bubbles at the O-ring seat, meaning water was still above that line. When bubbles stopped I knew water was below that element. Removed the upper element and removed the upper thermostat. Then I replaced both and replaced all the corresponding wires to it.

  7. Hi~
    When draining a hot water heater at a beach house for the winter months,should the plumber have opened the pressure relief valve in the process?…Ours was left closed and upon spring turn on, I found that the copper pipe from there is cracked…ugh…thanks~

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