Troubleshooting a Pilot Light in Water Heaters

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Troubleshooting pilot light problems on gas water heaters. How to fix the water heater when the light goes out, does not light, won't stay lit, or the pilot flame is too small or too large.


To prevent problems with the water heater pilot light, it is crucial to read the manufacturer's instructions carefully especially how to maintain the gas water heaters and how to light the pilot. Otherwise, if the pilot light is not functioning properly, the unit won’t turn ON and you won't have hot water. Note that most of the older and economy gas water heaters are equipped with the pilot, while newer, advanced models utilize a hot surface igniter which is more durable and reliable.

Note: Pilot light repair shouldn't be complicated, but if you don't have the right tools and skills, or need any assistance, contact a professional plumber.

Instructions for fast and easy repair

Things to consider

It is important to understand when troubleshooting the pilot light problems that gas heaters are equipped with the safety elements, such as the thermocouple, which is designed to shut the unit off automatically, when the flame is not present or it is extinguished for any reason.

pilot light on water heaters


Causes, problems, and troubleshooting pilot light tips

The pilot light goes out due to condensation

Most of today's energy efficient water heaters will produce a certain amount of condensate. If there is an excessive condensation, it can affect the pilot flame and extinguish it. The condensate, in this extreme case, is running down the flue tube and is dripping on the main burner, which results in the pilot outage.

The light goes out due to improper venting or air supply

Most of the time improper venting will cause the pilot outage on direct vent gas water heaters (DV). A down-draft from the ceiling fan or if there is a draft at the bottom of the unit can blow out the pilot also. If there is a restriction in the fresh air delivery, find the reason and remove the obstructions. The right amount of air should be delivered when the unit is installed in the small confined space. If the wind is blowing directly into the DV vent it may cause the pressure imbalance. If the water heater is installed in an attic, an excessive heat (above 120 C) could be another reason.

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The pilot does not light

One of the reasons why there is no hot water is when the burner did not ignite, and this is happening when the pilot light does not light. And here are the reasons:

  • If the pilot line is clogged, clean it or replace it.

  • Faulty piezo igniter. The water heater uses the piezo igniter to light the main gas burner and when it is pressed down, it releases the electric spark. The spark gap is factory set (0.125") and should be maintained. When troubleshooting the lighting problems, it is recommended to test it first. Turn the gas OFF to the water heater and press the piezo igniter. Once pressed, the electrode should release the spark.

  • Check if the wire connection is properly tightened.

  • Make sure the electrode is not broken, and replace it if it is.

  • Soot and/or carbon deposits on the pilot light. Clean the tip of the electrode from the dirt, rust, and other deposits by using the dry cloth and sandpaper.

  • No gas or faulty gas valve does not release the gas.

The pilot light will not remain lit

When troubleshooting the pilot light problems such as when it does not stay lit, keep in mind that there are often different causes for this and other conditions.

  • If there is no gas or the gas pressure is too high or low, check with your utility company.

  • If the pilot light tube and its orifice are clogged make sure to clean them.

  • The gas valve or its inner elements are faulty... replace it.

  • If the thermocouple connection is loose, tighten it, and if you have the faulty thermocouple, replace it with the new one. The gas control valve should be creating at least 10 millivolts.

  • The thermocouple should be embedded in the flame and tighten correctly - first hand tighten it and then use the wrench for additional 1/4 turn.

  • Replace the thermostat (gas control valve) if the thermostat ECO switch is open.

  • The air present in gas line could prevent the pilot light from lighting. Purging the air from the gas line should be performed by the professional.

The pilot flame is too large

The main reason why the flame is too large is if the gas pressure is too high. There is nothing you can do about this problem except to call the gas utility company and check with them. Another reason is the wrong size of the pilot burner orifice.

The pilot flame is too small

If the gas pressure is too low, the flame can become too small. Check with the utility company about this problem. Also, a pilot light tube and its orifice might be clogged with the dirt coming through the gas line. Some elements you can clean, but if there is dirt in the incoming gas line, you should notify your utility distributor and check with the gas technician about installing the dirt trap in the gas line. If you have the wrong pilot burner replace it with the correct one.

Important: Before troubleshooting the pilot light keep in mind that a pilot flame is always ON and the flame should be blue. If it is yellow, it needs an adjustment. Make sure that the tank is completely filled with water before lighting the pilot light.

Note: If you need a help, contact this plumbing company to send you a professional.

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Pilot light goes out after the water heater has been running for a few minutes. 
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