Why is My Gas Water Heater not Igniting, and How Can I Repair It?
Troubleshooting Tips

Fix a water heater that is not workingImage by Steve Buissinne from Pixabay

See why is your gas water heater not igniting and what you can do to repair it successfully.

If you have a problem with a gas water heater that doesn't turn on and there is no hot water in the house, use this comprehensive DIY troubleshooting guide to find the causes, symptoms, and solutions.

In order to ignite a gas water heater properly and have the unit running with no interruption, it is important to follow the ignition instructions found on the heater's label or manual.

Note: Gas can explode. Before working on the water heater, make sure the gas is off.

Instructions might be different from one brand and model to another. It also depends on the gas control valve type, where White Rodgers, Honeywell, and Robershaw are the most popular.

If a water heater is equipped with one of the mentioned gas control valves and it doesn't ignite, the following causes might be the reason:

Tip: The main indicator of the proper gas water heater operation and complete combustion is the stable light blue flame.

A gas water heater is not igniting because the pilot won't light

If a gas water heater is not heating, the most common problem is the pilot light. And here are several reasons why the pilot won't light:

  • Insufficient gas supply. Call your gas utility company to check if there is a problem with the gas supply on their end. They might also send a technician to check the gas meter at your house.
  • Low gas pressure. Contact your gas supplier to check if there is a problem with the gas pressure. They might also send a technician to check the gas meter at your house.
  • Incorrect dial position. A gas knob/dial is set to the wrong place. If trying to light the pilot, the knob should be in the PILOT position. If lighting the main burner, the knob should be in the ON position. Set the gas knob to the correct position using the lighting instruction or a manual.
  • The knob on the valve was not fully depressed when trying to light the pilot. Again, check the manual and lighting instructions for the proper operation.
  • Air in the gas line. If your gas water heater was recently installed, the gas line might be full of air and would require bleeding the air.
  • The pilot orifice is clogged. Clean or replace the orifice.
  • The pilot tube is clogged or damaged. Clean the pilot tube or replace it if needed.
  • The piezo igniter is not functioning. Replace the igniter.
  • The pilot electrode is not generating sparks. Replace the spark electrode if it is defective.
  • Faulty gas control valve. If the gas valve malfunctions, it may prevent gas from entering the burner.
  • Defective thermocouple or thermopile. This is what prevents the pilot from staying lit.

The pilot won't stay lit when the control knob is released

Thermocouple issues. Common problems that lead to pilot outages include dirty, bent, and damaged thermocouples. Due to dirt and mineral accumulations, a thermocouple might not provide sufficient electricity to keep the pilot lit. Use the fine-grit sandpaper and a cloth to clean it. Clean the pilot tube as well. A thermocouple must be appropriately installed in the provided bracket, tightened, free of kinks, and fully engaged into the pilot flame.

Open ECO. Use the multimeter (set in Ohms) to check the continuity of the Energy Cutoff Switch device – ECO. When the pilot heats the thermocouple, the small current circulates through the thermostat, and while making the complete electric circuit, it signals whether it is good or not. If there is no continuity, the ECO has opened, shutting off the gas supply. It happens when the water inside the tank overheats, which is when the temperature exceeds 190 F. If ECO is activated (tripped), the gas valve must be replaced.

Open TCO. The TCO or Thermal Cutoff switch responds to high or low temperatures. It is located in front of the combustion chamber, and when the inside temperature exceeds the maximum set temperature, it turns the unit off. A similar switch type can be installed on the vent pipe, shutting down the unit when the vents are blocked and causing excessive heat buildup. It is important to determine the cause of switch activation and eliminate it before resetting.

The pilot will light, but the gas burner won't come on

If the pilot light is on, but your gas water heater is not turning on, the temperature dial on the gas control valve or thermostat might be set too low. So, if the water temperature inside the tank is higher than the set temperature on the thermostat, the pilot could light, but you need to increase the settings so the unit can turn on. If your water heater is working and the hot water temperature meets the temperature on the thermostat, the unit turns off.

The pilot goes out occasionally

From time to time, the pilot might go out. And when it is out, your gas water heater will not ignite. The reasons for this problem include mostly blocked venting and insufficient air supply. This is why proper venting installation, including sizing and maximum length, are important. There should not be any diameter reduction, damages, and restrictions. Also, check and clean any dirt and debris accumulation on the arrestor plate and openings. Ensure that the air pressure switch is operational also.

Igniter issues

Sometimes gas water heater won't ignite because the igniter fails to ignite the gas. Check the igniter and make sure that is getting sufficient voltage. And if you confirm that the voltage is per requirements, but it doesn't glow, the element is defective and needs to be replaced.

Conclusion

As we can see, various problems can cause your gas water heater not igniting and stop the production of hot water. Whether it is a blown out pilot light, malfunctioning gas control valve, or faulty thermocouple, each element can be replaced by the DIY handyman.

If you have any doubts or are unsure how to deal with the problem, contact a licensed plumber to repair your water heater.

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