How to Replace a Leaking Water Heater Drain Valve

Turn Off the Power or Gas

• Turn off the power to an electric water heater by switching off the appropriate breaker in the home's electrical service panel (breaker box).
• Turn off the gas to a gas water heater by turning the pilot knob to the PILOT setting. This will prevent the burners from igniting but should keep the pilot light running so you don't have to restart it later. Alternatively, shut off the gas supply by closing the valve on the gas line near the water heater.

Let the water heater cool down for several hours before proceeding to draining the tank and replacing the drain valve.

Turn Off the Water Supply

Close the valve on the cold water supply pipe that leads to the water heater. There should be a valve on the line near the top of the heater tank. Alternately, the main water supply valve to your home can be shut off.

Drain the Tank

Connect a garden hose to the water heater's drain valve, and run the hose to a nearby floor drain or outdoors. Open the temperature and pressure relief valve (T&P valve) on the side or top of the tank by flipping the lever to the open position. This allows air into the tank to prevent suction that would inhibit draining.

Open the drain valve all the way to begin draining the tank. Some valves have handles; others have a slotted spindle that you turn with a flathead screwdriver. Be cautious while draining the tank, as the water may still be quite hot.

Let the tank drain completely, then close the T&P valve by flipping down its lever and letting it snap back to the closed position.

Remove the Old Drain Valve

Disconnect the hose from the drain valve. Remove the drain valve from the tank by turning it counterclockwise with a large adjustable wrench, pipe wrench, or channel-lock pliers.

Install the New Drain Valve

Wrap the threads of the new valve with plumber's tape and screw it into the tank's drain opening by hand. Tighten the valve with a wrench, stopping when the valve outlet is pointing downward, in the same position as the old valve. Confirm that the valve is completely closed by turning the handle fully in the clockwise direction.

Fill the Water Heater

Open the hot-water tap on any faucet inside the house. Open the valve on the cold water supply line to begin refilling the water heater's tank. When water flows out of the faucet, the tank is full, and you can close the faucet. 

Turn on the Power or Gas

Turn on the power to an electric heater, or turn the pilot knob to ON for a gas heater. The water heater will begin heating the water in the tank. If necessary, relight the pilot following the manufacturer's directions.

Check the Valve for Leaks

Check the new drain valve immediately for leaks, and check again periodically for the next day or so, just to make sure there are no problems with the valve.