Health Information and Tools > Health A-Z >  How Do I Flush My Water Heater?

Main Content

Water Safety

Flushing Your Water Heater

Follow the steps below to flush your water heater. If you have any problems, call a plumber.

  1. Turn the cold water valve (water supply) off. It is close to the top of the hot water tank.
  2. Turn the power off.
    • For electric water heaters, turn the power (at the circuit box) off before you do anything else. If there is no water in the water tank and the power is on, you can damage your water heater.
    • For natural gas water heaters, turn the gas valve on the tank to the pilot position or the lowest temperature setting.
  3. Attach a garden hose to the drain valve (water spigot) at the bottom of the water heater. Direct the hose towards the basement floor drain or outside. If you direct the water outside through a basement window, you might need a pump (unless you have a walkout basement).
  4. Open a hot water tap on the main floor in your house (or on a higher floor than your water tank). This will create pressure to help force water out of the water tank.
  5. Open the hot water tank drain valve. Let the water run out the garden hose. This can take 20 to 60 minutes, depending on how big the tank is. Be careful not to damage or break the drain valve when you open and close it. Never force the valve open or closed.
  6. When all the water has drained from the tank, turn on the cold water valve at the top of the tank 3 times. This will mix the sediment at the bottom of the tank around and help drain it out the garden hose. Sediment or scale can sometimes plug the drain valve, which prevents water from draining.
  7. Open and close the drain valve 3 times to get rid of all sediment. You can also use compressed air to force sediment out the drain and back into the tank. If you are not sure what to do or have problems, call a plumber.
  8. Repeat steps 1 to 6 until you see clear water draining from the hose. Leave the hot water tap you opened on while you do this. This will help remove any water that is blocked in the hot water lines.
  9. When you see clear water draining from the hose, close the tank drain valve. Do not force it or you might break it.
  10. Turn on the cold water valve (at the top of the tank) to refill the tank with water. When the tank is full, you will see a steady flow of water from the open hot water tap. When you see this, turn the hot water tap off.
  11. If you have a gas heater, turn the gas valve knob back on. If you have an electric heater, turn the power back on.
  12. Check the drain valve at the bottom of the water tank for leaking.  If it is leaking, open and close the drain valve a few times, in case there is sediment blocking the drain. You will see water draining out when you do this. If this does not work, turn the cold water supply to the tank off and call a plumber.

If you have any questions, call Environmental Public Health.

Current as of: March 12, 2018

Author: Environmental Public Health, Alberta Health Services