How to Turn Off a Gas Water Heater

It's always a good idea to shut off your gas water heater when you're going away for an extended period; it saves gas and overheating problems when you aren't there to take care of them. That's not the only reason you may need to shut your heater off, though. If you notice the pressure-relief valve spewing water or hear the hiss of gas from anywhere around the heater, shutting off the heater is an emergency procedure that can prevent a disaster. The procedure is simple, and it's important to know how to perform it.

Hand of a man turning down household gas water heater temperature.
credit: Serenethos/iStock/Getty Images
Rotate the gas valve to turn off the water heater.

Shut Off the Gas Control Valve

The gas control valve is usually red or black and is located on the front of the tank near the bottom. It may be hidden by insulation; if so, pull back the insulation to reveal it. The dial selector should be pointed to the "On" position. Turn the dial past the "Pilot" position to the "Off" position. This shuts off the pilot as well as preventing the burner from igniting. Remove the heat shield from under the valve and look inside -- you shouldn't see any flame from the pilot tube. If you only want to turn off the heater for a few minutes for servicing, turn the dial to "Pilot." The pilot flame will remain lit, but the burner won't cycle on.

Turn Off the Gas Line Valve

If you're leaving the house for an extended period, or you hear hissing coming from the heater, you should also turn off the gas valve in the gas supply line. You should see a shut-off valve on the gas line somewhere near the heater. Turn the gas valve 1/4 turn until the lever is perpendicular to the gas line to shut off the gas. If you don't see a valve near the heater, follow the gas line until you find one. You shouldn't have any trouble locating it because it's required to be in an accessible location. If you can't find it for some reason, turn off the main gas valve, which should be just inside or outside your home's foundation.

Shutting Down the Water Heater

If you plan to leave your house during the winter when temperatures might get cold enough to freeze the water in the tank, you should drain the heater as a precaution. It's best to wait for 12 hours after turning off the gas before doing this to avoid getting scalded, but if you can't wait, be sure to take appropriate precautions. Make sure that no one else is near the tank. To drain the tank:

  • Place a bucket under the open end of the pressure relief valve's discharge pipe. Open the pressure relief valve and hold it open until no more water or steam come out. Release the lever gently.
  • Attach a hose to the drain valve on the bottom of the tank.
  • Run the hose to a location where you can safely drain the water. It's usually best if this location is at a lower elevation. Draining the hot water into your garden is a way to avoid wasting it.
  • Close the cold water valve to the heater and open one or several hot-water faucets in the house.
  • Open the drain valve and wait for all the water to run out.
  • Close the faucets and the hot water outlet on the heater.

If the water won't drain, it's probably because mineral deposits are blocking the drain opening. Remove the hose and clear the deposits with a length of wire. Shut off the valve and reattach the hose as soon as the water starts running.