How To Fix Water Heater Delayed Ignition [4 Easy Solutions] 

Can hear a water heater boom sound? If yes, it is most likely caused by delayed ignition. For an easy water heater delayed ignition fix, check the pilot light, gas pressure, and draft, and clean the burners.

Remember you should not take delayed ignition at all. It is a serious safety hazard. So, know all about the delayed ignition right now and fix it ASAP.

Why Is Delayed Ignition Dangerous?

A delayed ignition means that when your heater is calling for hot water, the gas valves are opening and the gas supply is normal but this gas isn’t lighting up instantly as it should. 

So when the ignition is delayed, the gas gets a chance to build up. And when it finally does light up, you can hear your tankless water heater backfiring and making a loud noise like an explosion.

These explosions put enormous pressure on the components of your heater. So your heater can break. Not to mention what a safety hazard this situation is. You can get seriously burned.

If you are hearing your water heater going boom or crackling and popping during lighting, we urge you to not take that lightly. Almost 99% of the time, the reason behind this noise is delayed ignition.

Read this troubleshooting guide carefully to solve this ASAP. If you have some experience working with electric or gas heating appliances and the noises aren’t that intense, try our solution. If that doesn’t fix your issue, then call in a professional.

But in case, the explosions coming from your water heater are loud and intense enough to shake the floor, don’t go near it. Turn the heater off and call a professional. People have hurt themselves trying to light their pilot to fix a delayed ignition. It is a serious concern and results in a lot of flash burns every year in the US.

What Causes Delayed Ignition in Water Heaters?

The common reasons behind delayed ignitions are moisture build-up, sulfur build-up, dust, and debris build-up, too much primary air, restricted pilot light, etc.

Moisture build-up can block the ports through which gas is supplied by corroding the firebox. With blocked ports, your burner won’t get enough gas to light up promptly. But when it does finally light up there is excessive gas build-up which results in your water heater going boom.

Another cause can be a sulfur build-up. When you burn natural gases a certain amount of sulfur is left behind. You can spot a layer of white substance on your heater’s pilot light or burners if this is the cause for your water heater’s delayed ignition.

Dust and other small particles in your household can get carried to the pilot light or the ports and cause a blockage as well. Before ignition, if there is too much air mixing with gas, it makes lighting difficult and causes gas to build up. 

There can be many other reasons behind delayed ignition. But by now, you get a general idea of what could cause it. Now, Let’s look at how to fix delayed ignition.

How To Fix Water Heater Delayed Ignition [4 Easy Solutions]

Here we have a checklist for you that works 90 out of 100 times in stopping the crackling and popping noises coming out of a water heater. 

You’ll need to:

  • Inspect the pilot is lit properly
  • Check for proper gas pressure
  • Examine the draft
  • Remove and clean the burners

One or more items in this list can be the reason behind the issue. If the delayed ignition issue hasn’t been resolved after doing everything on the list, it is best to call in a professional for help.

How To Inspect The Pilot Light

For most units, the pilot light is found at the base of the unit. You have to remove the access cover to see if it is burning properly. If you see blue flames that means your pilot light is okay. 

If your pilot light isn’t that blue, there must be something wrong with it. Check out our easy guide to fixing pilot lights. After you resolve the issue with your pilot light, you’ll need to relight it.

Before relighting, check to see if you can smell gas. If you can, don’t go anywhere near the heater. You can contact a professional HVAC company to handle any possible leakage. But if you are sure there is no gas leakage, here’s how you properly re-light the pilot-

What you’ll need: a pair of pliers, a box of wooden matches, and a flashlight.

  • The first step to this is to turn the gas control knob to the off position. Usually, you’ll need to turn it clockwise to turn it off.
  • Now, you want to open or remove air access covers for the burning chamber using a pair of pliers or a wrench.
  • Next, use a flashlight to locate the pilot light. You want to make sure that you’ve got plenty of room to see what you’re doing.
  • And then use a match and turn the control knob to the pilot position. Immediately hold a match to the end of the pilot light while also pressing the reset button on the control.
  • If you see that you have a flame, wait for an entire minute and then simply release the reset button and turn it counterclockwise to the on position.
  • Now that you have the pilot light lit, all you need to do is put the access panels back in place.
  • And the last step is to set the thermostat at whatever temperature you like.

How To Check Gas Pressure

Your electric heater needs a certain amount of gas pressure to ignite properly. You can spot your water heater’s gas pressure rating on its sides. For a propane water heater, the rating will be high compared with a natural gas water heater.

The label will have a pressure rating for max inlet or line pressure, such as 16.0” W.C. This is the pressure rating of the incoming gas line. You’ll spot another rating that is of the manifold pressure. Manifold pressure means the gas pressure between the space starting from the gas control valve to the burner. 

You can find the incoming gas line pressure by contacting your gas utility company. Here’s how to test manifold pressure for maximum line pressure of 14.0 W.C. You’ll need a manometer:

  • Shut down the gas valve.
  • On the bottom or the side of the gas control valve, there is a pressure tap plug. Remove this plug and install a pressure tap. 
  • Connect the pressure tap to the manometer.
  • Now, light the main burner and note the reading on the manometer.
  • The natural gas operating range is 3.5-4.5 W.C. For L.P. gas, the operating range is 9.5-10.5 W.C.
  • If the pressure is normal, after shutting off the gas valve, removing the manometer and the pressure tap, replace the pressure tap plug as well.  

If the pressure is less than desired you can increase the size of the piping that supplies gas, and increase the setting on the supply gas pressure regulator. Likewise, for a pressure reading that is over the limit, lower the setting on the supply gas regulator or add another supply gas regulator.

How to Examine Your Water Heater Draft

To fix your tankless water heater delayed ignition problem, you should next test the draft. These are the steps to check if your water heater draft is working properly. You need to create a situation where the draft will be put to test by stopping airflow in your house as much as possible.

Here’s how we do it:

  • If your boiler or furnace shares a vent with the water heater, turn the heat down on them.
  • Close all the doors and windows in the room through which air can enter your home.
  • If you have any fireplace dampers in your house, close them.
  • Turn on all the exhaust fans in your house.
  • Turn on your clothes dryer.
  • Now, run a bath or open any faucet so that the water heater will turn on.

If in this extreme condition, your water heater’s performance is the same, then your water heater’s draft is fine. The problem is with something else.

How To Remove And Clean Burners

It is a good idea to clean your water heater burners now and then. Not cleaning them can lead to a build-up of dirt. Your gas line, orifice, and burner gas ports are vulnerable to dirt. Your unit won’t function properly. These are the steps you’ll need to follow and your burners will be cleaned in no time-

  • Put the gas valve in the OFF setting.
  • Take out your vacuum cleaner to clean the ring filter at the bottom of the unit. This filter blocks lint, dirt, and dust from getting into the system.
  • Take the inner door off.
  • Detach the main burner for cleaning.
  • Take a wire brush and clean the ports and orifice with it.
  • Now, by using compressed air, clean the flame arrestor plate and the combustion chamber.
  • Ensure that no large debris is inside the burner.
  • To clean the burners, you can safely use a vacuum cleaner, soap, and hot water.


Will a pilot light stay lit with a bad thermocouple?

Your pilot light will turn off if your heater has a bad thermocouple.

Does the gas leak if the pilot light goes out?

These days water heaters have a fail-safe device to prevent gas leaks when the pilot light goes out. But if your unit is an old model or your flame sensor is faulty, there could be a gas leak in that case.

Can you get carbon monoxide poisoning from a pilot light?

If incomplete combustion is happening in your heater, it may produce carbon monoxide. Install a carbon monoxide detector at your house to stay safe. 

How long does a thermocouple last?

They can last for years. Typically, you’ll have to replace them at least once during the lifespan of your water heater unit.

How much does it cost to leave the pilot light on?

That depends on the kind of gas your heater runs on. For natural gas, the monthly expense will be about $10. For propane gas that amount doubles each month. 


Hearing your water heater crackling and popping can be very scary. But hopefully, now you understand how to fix the water heater delayed ignition.

If you have further queries, comment below. We’ll do our best to come up with a helpful solution. 

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

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