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How to Flush or Drain a Water Heater

It’s important to flush or drain a water heater tank periodically to so the water heater will heat efficiently and produce ample hot water. Save money and time by handling this project yourself. Plan to do it once every two years.

Why is this necessary? Over time, mineral deposits collect at the base of a water heater tank. These deposits can build up to a very thick, crusty coating. This coating diminishes the transfer of heat from the burner to the water in the tank. Eventually, it also causes corrosion. Additionally, deposits can break free, clogging faucets, pipes, and the valve that is used to flush or empty the water heater tank.

Flush or Drain Tank, Step-by-Step:

1Turn off the water heater’s gas valve or electrical power, depending on whether it is a gas or electric heater.

gas electric water heater©Don Vandervort, HomeTips

Electric and Gas Water Heater Diagrams

drain a water heater©HomeTips

To drain a water heater, first attach a hose to the drain valve.

2Turn off the water inlet valve that controls the supply of water to the tank.

3Attach a hose to the drain valve at the bottom of the water heater, and run the hose to a drain, to the outdoors, or to a large bucket. Make sure the end of the hose is below the level of the drain valve.

Caution: Remember that the water exiting the water heater will be very hot! Be very careful to prevent scalding. If you want to be extra safe, allow the water heater to cool for many hours before doing the next step. 

HA Water-Heaters---Repair

4Open a hot water faucet somewhere in the house or the water heater’s pressure-release valve to let in air so the water heater can drain.

5Open the water heater’s drain valve. If you’re just flushing sediment, allow 3 or 4 gallons to exit until the water from the drain valve runs clear.

6Close the drain valve. Then turn the water supply valve back on to fill the tank, and turn the gas valve or electricity back on (relight the pilot or electronic ignition if applicable).

Water Heater Won’t Drain

If your water heater won’t drain when you open the drain valve, try opening the pressure-relief valve—this may break the vacuum that prevents the water from escaping. It’s a likely possibility that the drain valve may not be working because it is clogged with mineral deposits. For step-by-step information on solving this, please see the HomeTips article, Water Heater Won’t Drain.

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Join the Conversation

  • scott

    I have a indirect water heater with no drain valve…How do I flush it?

    • Don Vandervort, HomeTips

      Hi Scott. Not sure what you mean by “indirect.” Do you mean you have a tankless or point-of-use water heater? These types are not flushed like a tank-style water heater.

  • Rick

    When I drain/flush my gas water heater, is it necessary to turn off the gas or can I just set it to Pilot? Re-lighting is difficult because of the tank’s positioning, so I’d prefer to turn it off only if it’s really important.

    • Don Vandervort, HomeTips

      Normally, I think it’s best to turn the gas off, but If you’re just flushing it, turning it to pilot so that the burner’s don’t fire should be okay.

  • Solid

    My water heater quit working today. I went to investigate and noticed that the softner brine tank was leaking water out of the overflow and the water was splattering up against the bottom of the water heater. There is slat deposits all along the bottom of the water heater.

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