The only tool needed to drain a water heater is a garden hose. Draining a hot water tank is a simple four-step process that only takes about two hours.
The first step in draining the water heater is to turn off the power supply. For an electric heater, this is done at the breaker box, but for a gas heater, the thermostat should be set to the Pilot setting. The garden hose can then be connected to the drain valve, but the valve should not be open yet. The cold-water supply should also be turned off.
In order to avoid creating a vacuum, one of the hot-water faucets in a sink or bathtub should be turned on. When this is done, a person can open the valve to drain the water out of the tank through the hose. It is best that the other end of the hose is flowing outside, or into a drain where hot water cannot harm anything or anyone.
When the water stops flowing, the water supply should be restored in order to flush out the tank. When the water runs clear, the drain valve can be closed, and the hot-water faucet should be turned off. The power should be returned to the heater, and the pressure-release valve should be tested before fully using the tank again.