Turn off the water heater power or gas supply
Turn off the cold water supply to the heater
Let the water cool if needed
Connect a garden hose to the drain valve
Place the other end of the hose in a safe drainage area
Open a hot water faucet in the house
Open the drain valve on the water heater
Let the tank drain completely
Briefly open the cold water supply to stir up sediment
Repeat draining until water runs clear
Close the drain valve
Remove the hose
Close the open hot water faucet
Refill the tank by turning on the cold water supply
Check for leaks
Restore power or relight the pilot if applicable