How To Drain a Water Heater

Is your gas or electric water heater making a “knocking” sound?  That’s a common occurrence that can happen with the unit after a few years of use.  Even the best water heaters on the market, including top brands like Rheem, Whirlpool, Bradford White, Richmond, and A.O. Smith, can develop this noise depending on the quality of your community’s water supply.

Why is my water heater making noises?

If the water supply coming into your home contains an abundance of minerals, it is considered “hard”. The minerals, or sediment, in hard water will eventually begin collecting at the bottom of the water heater tank. As the sediment builds up, it will trap water underneath it. When the water is heated by the gas burner or the heating elements, steam bubbles will rise up and erupt through the layer of sediment, creating that annoying “knocking” or “popping” sound.

Since the build-up of sediment can reduce the efficiency of the water heater, and eventually damage the interior lining of the tank, it’s a good idea to drain the water from the tank every one or two years to flush out these mineral deposits. You’ll not only eliminate that “knocking” sound, but you’ll extend the life of your water heater.

Draining the water heater tank

Water heaters have two outlet valves: a temperature and pressure relief valve located near the top of the tank, and a drain valve located near the bottom of the unit. The drain valve is the one you’ll open to flush out the tank. Before you attempt this, be sure to unplug the water heater’s power cord, or shut off the power supply to the unit. If you have a gas water heater, you should shut off the gas supply to the unit as well. Allow some time for the hot water in the tank to cool down.

  • Close the intake valve located on the cold water intake pipe on the top of the tank.
  • Attach a garden hose to the drain valve spigot, positioning the opposite end of the hose near a floor drain.
  • Open a hot water faucet elsewhere in the home to alleviate pressure. This will assist with the discharge of the water from the tank.
  • Open the drain valve to drain the water.
  • Once the water in the tank has completely drained out, open the cold water intake valve to help flush out any remaining sediment.
  • When the water coming out of the hose appears completely clear, close the drain valve and remove the hose.
  • Leave the cold water intake valve open to refill the tank.
  • Turn off the hot water faucet elsewhere in the home.
  • Turn the gas supply back on, if applicable, and restore power to the water heater.

Checking the water heater for leaks

After draining the water heater tank, you should confirm there are no leaks coming from the drain valve. Sometimes loose sediment will prevent the valve from closing all the way, resulting in the valve developing a slight drip. You can place a cap on the spigot to control the dripping. However, if either the drain valve or the pressure relief valve is leaking significantly, you should replace the valve with a new one.

Find the right water heater parts with Repair Clinic

Repair Clinic stocks the specific heating & cooling replacement parts that fit your water heater model, including those manufactured by Rheem, A.O. Smith, Bradford White, Richmond, or Whirlpool. Type the full model number of your water heater into Repair Clinic’s search bar for a complete list of parts compatible with your unit. You can also explore Repair Clinic’s repair help library for additional information concerning common problems affecting water heaters, how to test certain components, and how to install new parts.

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