Guides and Tips

8 Reasons Why Your Water Heater’s Burner Won’t Ignite

July 12, 2023
8 Reasons Why Your Water Heater’s Burner Won’t Ignite

There’s nothing quite as disheartening as ice-cold water blasting down the shower when all you want is a hot, soothing bath. It’s even more frustrating when you try to open the water heater, and only the pilot light lights up while the burner remains unlit.

The cause of this frustration typically lies in a handful of reasons, each with its own solution, and yes, we’ll tell you all about them in this guide!

Parts of a Water Heater

Before we explore the possible reasons why your burner won’t ignite even when your pilot light is on, it’s important to familiarize yourself with the different parts of the heater to be able to follow the fixes we discussed below. 

Your water heater should come with a manual that identifies the different parts and functions of your heater, so it’s best to refer to that. However, if you’ve lost the manual, you can refer to this video:

Why is my pilot light on but my burner won’t light?

Rusty Thermocouple or Thermopile

Rusty Thermocouple or Thermopile

Thermocouples and thermopiles are responsible for measuring temperature and closing off the gas line to the water heater, so if they’re not functioning properly, your water heater system will also not work as intended.

If the thermocouple or thermopile is covered in rust, it will be hard for the component to sense heat from the pilot light. If it can’t sense heat, it will automatically close the gas valve to stop the gas from going to the combustion chamber.

As such, the burner will not ignite even if the pilot light is open.

How to Fix It

DifficultyMedium ●●●○○
Number of steps9
Time required20 to 30 minutes
Things you needWrench, emery cloth, and lint-free cloth

Step 1: Turn off the gas valve and pilot light.

Step 2: Dismantle the cover plate.

Step 3: Take a picture of your burner assembly as a reference.

Step 4: Disconnect the pilot light supply tube.

Step 5: Disconnect the wires connected to the control center.

Step 6: Slide the burner assembly out of the water heater.

Step 6: Check if the thermocouple or thermopile is dirty and rusty.

Step 7: If the thermocouple or thermopile is dirty and rusty, gently sand the end of it with an emery cloth.

Step 8: Clean the thermocouple or thermopile with a lint-free cloth for a thorough cleaning.

Step 9: Reassemble the burner assembly.

Corroded Burner Jet

Corroded Burner Jet

Corrosion in the burner jet can disrupt the proper flow of gas, leading to reduced combustion efficiency. The burner may struggle to produce a consistent flame, resulting in incomplete or inefficient heating of the water.

If the corrosion is severe and there’s also debris in the burner jet, the burner may not ignite at all. This is why even if the pilot light is lit up, you won’t find the burner igniting as it’s supposed to.

How to Fix it

DifficultyMedium ●●●○○
Number of steps10
Time required30 to 60 minutes
Things you needWrench, sponge, towel, baking soda, and dish detergent

Step 1: Switch off the gas supply.

Step 2: Remove the burner access cover.

Step 3: Disconnect the burner tube from the control valve.

Step 4: Disconnect the igniter and other wires from the valve.

Step 5: Pull the burner out of the heater.

Step 6: Check if the burner jet is corroded.

Step 7: Remove all the debris in the burner jet.

Step 8: Wash the burner jet with warm water and gently scrub it with a sponge. Use a few drops of dish detergent and baking soda to easily remove rust.

Step 9: Dry the burner with a towel. Make sure it’s completely dry before putting it back in the heater.

Step 10: Reassemble the water heater.

Clogged Burner Orifice

Clogged Burner Orifice

The burner orifice is a small hole that’s responsible for distributing gas to the burner tube. It allows a precise amount of gas to mix with the surrounding air to create combustion.

If the orifice is clogged, there won’t be enough gas to start combustion. This means the burner won’t be able to ignite.

How to Fix it

DifficultyMedium ●●●○○
Number of steps8
Time required30 minutes
Things you needWrench, air compressor

Step 1: Unplug the heater and turn off the gas supply.

Step 2: Take off the burner cover.

Step 3: Detach the burner tube from the control valve.

Step 4: Disconnect other wires from the valve.

Step 5: Take the burner out of the heater.

Step 6: Take off all the debris in the burner.

Step 7: Use a bottle air compressor to blow off any debris in the orifice.

Step 8: Reassemble the water heater.

Dirty Heater Filter

Dirty Heater Filter

A filter helps regulate airflow in a water heater and makes sure it receives a sufficient amount of oxygen for its combustion process. 

A clogged filter can restrict airflow and result in the heater not receiving enough oxygen to start combustion. This can cause the burner to not ignite even when the pilot light is lit.

How to Fix it

DifficultyMedium ●●●○○
Number of steps7
Time required30 minutes
Things you needWrench, air compressor, vacuum

Step 1: Unplug the heater and shut off the gas supply.

Step 2: Remove the burner cover.

Step 3: Disconnect all the wires connecting the control valve and the burner.

Step 4: Detach the burner from the heater to gain access to the filter. The filter is the surface below the burner.

Step 5: Use an air compressor to loosen and remove the debris in the filter.

Step 6: Vacuum out the remaining debris in the filter.

Step 7: Reassemble the water heater.

Thermostat or gas control valve is malfunctioning

Thermostat or gas control valve is malfunctioning

The thermostat is responsible for regulating the temperature of the water. However, just like any equipment, it can get worn out too and lose accuracy.

It may not be able to send a signal to the burner to ignite because of inaccurate temperature measurement. This may sometimes cause both the burner and the pilot light to malfunction.

However, there are some instances when the burner is the only one affected and the pilot light is working just fine.

Even if the thermostat is still working properly, the burner may still not ignite if the gas control valve is damaged. 

If any of the two is damaged in a gas water heater, you’ll have to replace the control valve.

How to Fix It

How to Fix Broken Thermostat
DifficultyVery Easy ●○○○○
Number of steps4
Time required5 minutes

Step 1: Put the thermostat on “low” or “away” mode.

Step 2: Put it at the standard temperature prescribed by the manufacturer.

Step 3: Check if the burner ignites. If not, put it on “low” or “away” mode again.

Step 4: Put the thermostat a few degrees above the standard. This should ignite the burner if the thermostat is the problem.

This is just a temporary solution to this problem. If the thermostat is the reason your burner won’t ignite, then you need to have it replaced.

Here’s how you can replace the thermostat and the control valve:

How to Replace Thermostat and Control Valve
DifficultyMedium ●●●○○
Number of steps8
Time required2 to 3 hours
Things you needWrench, water hose, new thermostat

Step 1: Drain the water heater.

Step 2: Disconnect the gas line, burner, pilot, and thermocouple from the thermostat.

Step 3: Remove the burner from the water heater.

Step 4: Remove the old thermostat.

Step 5: Install the new thermostat.

Step 6: Put the burner back into the water heater.

Step 7: Reconnect the gas line, burner, pilot, and thermocouple to the new thermostat.

Step 8: Try if the new thermostat is working.

Malfunctioning Automatic Gas Shutoff

Malfunctioning Automatic Gas Shutoff

The automatic gas shutoff is a safety feature water heaters have that automatically stops the gas supply when it detects leaks or other abnormalities in the water heater.

If the automatic gas shutoff is malfunctioning, it can shut off the gas supply even when there’s no gas leak or abnormalities in the other components. This means the burner won’t ignite even if you turn on the pilot light.

How to Fix it

Fixing the automatic gas shutoff component is complicated and must be left to the hands of professionals. If you try to fix it on your own, you may do more damage, and it can also lead to a hazardous situation that can harm your entire household.

Blocked Gas Line

Blocked Gas Line

Another possible reason why the burner won’t ignite despite the pilot light being lit up is a blocked gas line.

When the gas line is blocked by debris or dirt, gas flow is interrupted. As a result, the burner won’t receive the required amount of gas to produce a flame.

How to Fix it

If you suspect that the reason behind your water heater problem is a clogged gas line, turn off the gas supply immediately and call for a professional to help you. 

This can be a safety hazard that can lead to fire or explosion if the pressure inside the line becomes too much.

Trying to fix it yourself may just cause more harm. Although you can clear it up with a wire, some more problems may arise, so it’s best to call the professionals.

The water heating system is too old

The water heating system is too old

If your water heater has been around for 12 years, then the problem may not just be one component but more. The heating system has probably gone past its useful life and needs replacement.

Problems caused by a worn-out water heater don’t just end with the burner not igniting. You may start encountering more, so fixing it will not be worth it.

How to Fix it

The only way to fix this problem is by replacing the whole water heating system and retiring the old one.

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