Turning off the gas to the water heater is simple. To do this, you simply find the incoming gas line and locate the shut off valve (In most cases, this will be found on the left hand side of the water heater, facing the heater). Do not confuse a shut off for another appliance with the one for the water heater. To be sure, just follow the gas line from the water heater thermostat control back until you come to the shut off valve. Most modern gas shut off valves are hand operated, however some older models may require the use of a wrench of some sort to turn off the gas.
Red handle lines up with pipe: Gas is on.
To turn off the valve, simply turn the T- Handle 1/4 turn until the handle is perpendicular or “cross ways” with the pipe. The gas is now OFF to the water heater.
Red handle crosses pipe: Gas is off.