- You will first need to turn off the water heater. For an electric water heater, turn off the power at the breaker box. For a gas water heater, switch the water heater to pilot. This will keep the pilot light lit but keep the water heater from heating any water. You can damage your water heater if you don't turn it off.
- Turn off the water supply to the heater by closing the cold water intake valve which is usually located on the pipes coming into the water heater.
- Remove the pressure in the system by turning on a hot water faucet. The water coming out may spurt and sputter until all the pressure is released. Leave the faucet on to help speed the next step.
- Connect a garden hose to the drain valve on the water heater and open the valve. Gravity is doing all the work so the end of the hose needs to be lower then the bottom of the water heater to fully drain the tank. You can catch some of the water in a bucket if you want to see how much sediment is coming out. The tank may take up to an hour to drain.
- Once the tank has drained, it is time to flush the system. First turn off the hot water faucet you turned on in step 3. Then open the cold water inlet valve you closed in step 2 and let the water run for five to ten minutes.
- To get the system back in working order, turn off the drain valve you opened in step 4 and allow all the water to drain from the garden hose. Remove the hose. Once the water heater as filled with water, turn the breaker back on for an electric water heater or set the temperature to the correct setting on a gas water heater.
- Turn a hot water faucet on to re-pressurize the system. At first the water may spurt and sputter until all the air is forced out of the pipes.
Consult your hot water heater's manual for the exact locations of all the parts and specific instructions for your heater.