You have to drain your water heater whenever you need to move it, and draining might become necessary if the tank fills with lime deposits or the water gets contaminated with odor-causing bacteria. To prevent problems such as these, manufacturers recommend draining your water heater annually. No matter which brand your water heater is, it has a drain valve located near the bottom with standard hose threads so you can attach a hose to route the water away.
If you have an electric model, turn off the breaker that controls the water heater in the main service panel (breaker box). If it's a gas model, turn off the gas control knob on the front of the tank, then turn off the gas supply valve on the gas line leading to the heater.
Find the cold water inlet valve; it's usually above the heater connected to the pipe the pipe that passes through the blue port on the tank. Turn it off.
Screw a garden hose to the drain valve on the bottom of the tank. The hose should be long enough to reach outside or, if you're in a basement, to a sink or floor drain. If you don't have another draining option, route the hose into a 5-gallon bucket. Open the drain valve all the way.
Lift the handle on the temperature and pressure relief valve to allow air into the tank. You can also loosen the hot water outlet connection on the top of the tank, using a wrench, or simply open a nearby hot water faucet. Water should begin draining as soon as air can get into the tank.
Allow the tank to drain completely. If you're emptying water into a bucket, you'll have to turn off the drain valve periodically to empty the bucket. Don't fill the bucket too full, making it heavy and difficult to carry without spilling.
Leave the drain valve open and turn on the cold water valve. Let water flow for a minute or so to flush sediment from the bottom of the tank.
The Tank Won't Drain
If no water flows when both the drain valve and an air admittance valve are open, it's usually because sediment is blocking the drain valve. To clear the sediment, leave the drain valve open, but close the one admitting air. Disconnect the hose and put a small bucket under the drain valve, then poke a screwdriver, dowel or straightened-out wire clothes hanger into valve opening. When water begins dribbling, open the air-admittance valve to allow the water to flush out the sediment. Turn off the drain valve and reconnect the hose as soon as water is flowing.