Troubleshooting Pilot Light in Water Heating

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, pilot flame is too small or too large.


To prevent problems with the water heater pilot light, it is crucial that you read the manufacturer instructions carefully; how to maintain gas water heaters and how to light it.

Instructions for repair

Things to consider

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

pilot light on water heaters


Causes, problems and troubleshooting pilot light

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 light and extinguish it. 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. 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 proper air supply 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.


emergency plumber

Pilot does not light

One of the reasons why you don't have a 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 pressed it releases the electric spark. The spark gap is factory set (0.125"). 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 the wire connection is it properly tightened.
  • Make sure the electrode is not broken... replace 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.

Pilot light will not remain lit

When troubleshooting 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 gas pressure is too high or low, check with your utility company.
  • If the pilot light tube and its orifice are clogged you should 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 milivolts.
  • 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 gas line should be performed by the professional.

Pilot flame 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.

Pilot flame too small

If the gas pressure is too low, than you might experience the flame being too small. Check with the utility company about this problem. Also, pilot light tube, its orifice might be clogged with the dirt found in 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 pilot light problems keep in mind that pilot flame is always ON and the flame should be mostly blue. If it is yellow it needs adjustment. Make sure that the tank is completely filled with water before lighting the pilot light.


Related Articles

Home > Troubleshooting water heaters > Fixing pilot light