How to Flush a Gas Water Heater Out

Flushing your gas water heater is a fairly simple task but also an extremely important one.

Doing so will not only ensure your water heater performs properly but also protects against premature failure. Over time, sediment, such as rust, calcium, iron and dirt, build up in the bottom of your water heater. The accumulation of sediment makes your hot water heater work harder, therefore increasing its operating costs. Sediment will also take up space in the tank, reducing the amount of available hot water. You should flush out your gas water heater every four months to prevent excess sediment buildup.

Locate the red temperature dial on the front of your gas water heater and turn it to the vacation setting. This will prevent the burner from going on while you are flushing the water heater.

Turn the cold water inlet valve on the top of the water tank into the off position.

Connect the garden hose to the hose bib at the bottom of the hot water heater. Run the other side of the hose either outside, or, if you have a floor drain nearby, place the end of the hose in the floor drain.

Open the valve on the drain valve at the bottom of the tank and completely drain the hot water heater. Once no more water is coming out of the hose, close the drain valve.

Turn the cold water inlet valve to the on position to refill the hot water heater, then close the cold water inlet valve.

Open the drain valve at the bottom of the hot water heater to flush the tank again to remove any remaining sediment. Once the tank is drained, close the valve and remove the garden hose.

Open the cold water inlet valve and set the temperature dial to the desired hot water temperature.

Things You Will Need

  • Garden hose
  • Pipe wrench


  • If your gas hot water heater has a flexible hose at the top of the unit that's attached to the cold water inlet, you can use a pipe wrench to disconnect it and move it out of the way. Doing so will relieve some pressure in the tank and allow it to drain a bit easier.


  • The water coming out of the hose from the hot water heater is extremely hot, so keep others away from it to prevent from getting burned.

About the Author
