It can take anywhere from half an hour up to several hours to completely drain a water heater, depending on the size of the water heater and access to the water shutoff and drain valves. To begin, turn off the cold water supply to the water heater, and then connect a garden hose to the drain valve located at the bottom of the water heater. You should also open a hot water faucet in a sink or tub before draining the heater. Open the drain valve to allow the water to flow out and monitor the draining water level as the tank empties. When the level of water has dropped to the indicator near the bottom of the tank, the water heater has been completely drained. Turn off the hot water faucet and remove the garden hose from the drain valve. Shut off the drain valve until you’re ready to fill the water heater with water.
Depending on where the water is going, you may need to continue draining the water for several minutes to allow any residual sediment or rust to flush out of the heater and water lines. Make sure to plug the end of the hose if you are draining into an area with plants, pets or children. Once the water is completely drained and the area is safe, you can refill the water heater, turn on the cold water supply and turn it on.
