To empty a water heater, you can follow these steps:

1. Turn off the power or gas to the water heater.
2. Connect a garden hose to the drain valve and open the valve to allow the water to drain out completely.
3. Open the pressure relief valves to help the water flow out.
4. Turn the water supply back on to flush out any remaining sediment.
5. Finally, close up the valves, restore the power or gas, and you’re done. The process takes about 20-25 minutes.