Turn off power to the water heater (set thermostat to lowest for gas heaters; switch off breaker for electric heaters)
Turn off the cold-water supply valve to the water heater
Connect a garden hose to the drain valve at the bottom of the tank
Place the other end of the hose into a drain area or outside where hot water discharge is safe
Open a hot-water faucet in the house (helps relieve pressure and lets the tank drain faster)
Open the drain valve on the water heater
Allow the tank to drain fully or until water runs clear
Close the drain valve
Open the cold-water supply valve to refill the tank
Keep the hot-water faucet open until a steady stream of water flows (no sputtering)
Close the hot-water faucet
Restore power to the water heater (turn thermostat back up for gas; turn breaker back on for electric)
Check for leaks around the drain valve and connections
Verify hot water operation