Has your gas water heater stopped heating water or become far less efficient at heating? Is there a soot buildup happening inside or around your unit? Is gas flowing into your unit even when the burner is off? If you answered "yes" to one or more of these problems, you might have an issue with the combination control valve and need to replace it before using the water heater again.

Note that replacing parts on an appliance that combines gas and electricity is dangerous if you don't know what you're doing. Don't have any prior water heater repair experience? Call in a professional that deals with water heaters to diagnose and fix your problem.

Have experience and feel fairly sure the combination control valve is your problem? Turn off the electric and gas supplies to the unit and start on the road to replacement.

What You Need:

• Owner's manual
• Garden Hose
• Replacement combination control valve

Step 1: Draining the Tank and Freeing the Valve

Double check that the gas and electricity are turned off before starting. Consult your owner's manual if you need a reminder on where the combination control valve is located in your unit and how the valve is held into position.

Now you need to drain all of the water out of the tank. Hook a garden hose up to the drain valve at the bottom of the tank. Place the other end of the hose in a drain pipe, sink, or out a window where the water won't flood your foundation. Turn the drain valve to allow the water to start to drain out of the tank.

While the tank is draining, you can start unhooking the various parts that hold or block the combination control valve into place.

Remove the wire connected to the igniter then remove its button and bracket. Pull out the manifold tube and set it safely aside followed by the pilot tube. Then disconnect the thermocouple, union between the shutoff valve and the combination valve, and the pipe sticking into the combination valve. Consult your owner's manual if you have trouble locating any of these pieces. 

Step 2: Removing and Replacing the Valve

Now that the valve is unhooked and the water is drained from the tank, you can actually remove and replace the valve. Good news is that the valve simply twists off in a counterclockwise motion. And the new one twists on using a clockwise motion.

Then you get to hook everything back up to the new valve. You just need to work in the opposite order outlined in Step 1. Make sure you use plumber's tape on the ends of the pipe to ensure that no water can seep through. Otherwise, just hook everything back up and/or put it back into place.

You can then unhook the hose and turn off the drain valve for the tank so that you don't have a flood on your hands once you turn the water supply back on.

Step 3: Restoring Your Unit

Turn on a faucet near the water heater to help depressurize the tank. Turn back on the gas and water supplies then wait for the tank to fill up for water.