Water Heater Gas Valve
Water heater gas valve problems can be diagnosed by checking the millivolts with a meter, however you can check a gas valve without a meter.
The guide below will show you how a gas valve works and what it should do and when it should do it. Once you know how it works you can diagnose the problem.
These valves are also called control valves, gas thermostats, and gas control valves.
How they work
The gas valve controls the pilot light and the water temperature
There are two probes protruding out of the back of the valve.
The longer probe is the temperature probe. As the water heats and cools a rod inside the probe pushes a lever in the gas valve and cuts the gas on and off according the the temperature setting.
Different Styles Of Gas Valves
In this pic. you can see the limit and
The pilot button on the valve is separate from the control knob.
The control knob must be turned to the pilot position before the pilot button can be pressed.
This control valve is on a newer style
water heater (has a sealed burner
This is a newer style water heater with an unusual control valve.
Notice the two white wires coming
out of the bottom of the valve.
To replace this valve you would need an exact replacement in order to wire up the roll-out switch.
Water Heater Gas Control Valve Troubleshooting
A water heater gas valve controls the pilot light, water temperature and it has a
safety limit to shut everything down.
Press the pilot button down and light the pilot.
If the thermocouple has been replaced and it has been properly installed (tip of the probe in pilot flame, thermocouple screwed in tight at the control valve,thermocouple line not kinked) and still the pilot will not stay lit when you release the pilot button then the gas control valve is at fault.
If the pilot will not light at all with the pilot button down check the gas supply.
You have gas and the pilot still will not light, the pilot line or orifice may be clogged.
Water Heater Temperature Control
This is caused by short cycling. What this means is that just enough hot water has been used to cause the thermostat to come on. Cold water has been dumped in the bottom of the tank near the thermostat. So, while this water is heating, the temperature in the top of the tank is rising.
If you find your water much hotter at times this is probably the reason
and not the water heater gas valve.
If the pilot is lit, you have a tank of cold water, the thermostat turned up and the burner does not fire up, either the burner orifice is clogged or the water heater gas valve is bad.
Remove the burner assembly. The orifice is located at the end of the burner supply line under the burner. Check the burner supply tube also.
Other Water Heater Gas Valve Problems
Gas control valves cannot be repaired. If a valve malfunctions it must be replaced.
If the pilot button does not pop-up when you release it, cut the gas off and replace the gas valve.
If the control knob will not turn don't force it. Replace the valve.
If the high limit has shut the gas valve down the valve must be replaced. It will not reset itself. This will only happen if the thermostat has malfunctioned and the water reaches extreme temperatures, in which case the gas control valve would need to be replaced anyway.
Gas can be extremely dangerous to work with if you're not sure about what your doing. At the same time, its safe to work with if you do know what your doing and follow all safety rules. If you do not feel 100 percent confident and understand safety precautions, please call someone to help you.
Always check gas lines for leaks after reinstalling them. Soap and water works well. Spray it on all connections and watch for tiny bubbles to form. If you do see bubbles tighten the connection and test again.
Before lighting a pilot stand near the water heater to see if you can
smell gas. Kneel near the gas valve and smell for gas.
Never fire a water heater burner with the access panels off.
Never tap or hammer on a water heater gas valve.
Related pages. Water heater pilot light
Water heater pilot light- How to light the pilot on older style water heaters.
Hot water heater pilot light- How to light the pilot on newer style water heaters.