Reasons As To Why The Water Heater Won’t Stay Lit

A water heater is designed to serve you efficiently, but after some time it might get faulty in lighting thereby resulting in poor performance. It is disappointing when you expect your water heater to serve you but fails in doing so.

Just like other electronics, water heaters as well are prone to service disruption that arises from the electric connection flaws. According to, this can be one of the cons of a tankless water heater. In case your heater surprises you with a lighting malfunction, don’t panic. There are ways in which the problem can be solved to get your water heater into its normal functional state.

A water heater's lighting failure can be attributed to some reasons. It could be parts that need fixing or replacement. I have brought forth in this article, some of the major reasons that may raise concern.

They include obstruction within the thermocouple, a curved thermocouple, a damaged thermocouple, a lousy pilot tube, an issue/problem in the flex tube as well as fault in the main control valve.

Reasons Causing The Water Heater's Lighting Problem

In finding a lasting solution to your water heater's lighting problem, you have to determine the source of the issue. I will outline and explain the various parts that could be causing you the lighting trouble. Afterward, you can decide on the measures to take in solving the problem.

1. Obstruction Within The Thermocouple

The thermocouple is central to a water heater's operation and can determine whether the pilot light is on or off using an electrical current powered by the pilot's heat. This device is important since many water heaters depend on it for an operation to take place.

As a safety precaution, the thermocouple turns off the gas in case it detects an unlit pilot. However, if the thermocouple is dirty, the electric current from the pilot may not be received, and this may lead to a gas outage. In dealing with this, you can use a sand paper to clean the thermocouple.

When you begin cleaning, make sure the thermocouple is cool enough for you to touch and also ensure the gas is off. Having the gas off and the thermocouple cool reduces the probability of an unexpected eventuality.

2. A Damaged Thermocouple

You can only arrive at this particular conclusion after ruling out all other possible causes of the water heater's lighting problem caused by the thermocouple. If the thermocouple is not dirty or bent, then the problem could be emanating from itself.

The thermocouple could be broken, and the only way of dealing with the problem is replacing it. While doing the replacement, ensure that the gas is turned off and the thermocouple is cool enough for you to touch.

Once you’ve done this, remove the furnace cover then unscrew the thermocouple. However, you can determine how bad the thermocouple is by testing the voltage coming from it. In case the reading is below 20 MV, the thermocouple is not in good shape.

3. A Curved Thermocouple

The normal functioning of a thermocouple can be impaired by a slight bend in its stature. If the thermocouple is twisted way too far from the pilot, it might end up not registering its heat.

In rectifying this problem, you can simply bend it back to its normal position to be close enough to the pilot's flame. The pilot's flame should gently touch the thermocouple to heat the device. Check the pilot light; it should be blue in appearance. The light should wrap around the sensor.

4. Flex Tube Problem

An issue in the flex tube may prevent the pilot from staying lit. The flex tube is responsible for ensuring a steady gas steam, and it connects the gas controller. Flex tube problems rarely occur and can only be looked into after the thermocouple problem has been ruled out.

When you ascertain that the problem is caused by the tubing, you can replace the tube with a new one. However, the flex tube could be in need of some little adjustment for proper operation. Doing so should solve the pilot`s lighting problem.

5. A Lousy Pilot Tube

If the water heater's lighting problem isn’t being caused by the thermocouple, the pilot tube could be the source of the problem. Dirt can build up in the pilot tube. When this happens, the proper flow of gas is hindered.

Amazingly, the process of dealing with this problem is easy. The process is quite simple in that; it entails turning off the gas and waiting for the pilot to cool down. After the pilot cools down, you can then take a needle and use it in cleaning up the tube.

After you are done with cleaning, turn everything on and check whether the pilot will light. If it doesn’t, repeat the cleaning process thoroughly for the pilot to light up.

6. Fault In The Main Control Valve

An issue with the main control valve could be the reason a pilot won’t stay lit though in rare cases. The main control valve doesn't go out thereby making it the last area of consideration after all other possibilities are explored.

In case the main control valve is faulty, another one is needed, for the problem to be completely solved. Replacement is the only solution to a faulty main control valve. In ascertaining that the main control valve is the reason the water heater won’t stay lit, first rule out the possibility of a thermocouple problem.


In case your water heater doesn't stay lit, look into the reasons explained above. Your water heater could require an adjustment or replacement to fix the problem.

After you look into the various reasons, rule out those that are unlikely by checking into each. In doing so, you will come up with the best solution.

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