Tankless Water Heater Won’t Ignite – Detailed And Easy Fix

Tankless water heaters are a great investment as they provide heat to warm up the water instantly. The best thing about a tankless water heater is that it saves your money by only heating water when needed. But, still, there are some issues that you may face with these heaters. And one of the most common issues is tankless water heater won’t ignite. Ignition failure is one of the most common problems where you need to get the proper information and guidance in order to deal with the problem.

There are many reasons behind the complaint about flame loss or the water heater not working properly. Before we go into details and conclusion you need to know how the tankless water heater works and what are the causes behind its ignition failure. Also, what are the steps to solve the complications when a tankless water heater fails to ignite? Follow the article to know the precise solution to the problem you are facing.

Tankless Water Heater Fails To Ignite – Detailed Answer

When a tankless water heater fails to ignite, there are many reasons behind this problem. To know the solution to these problems you need to have proper knowledge of how the tankless water heater works. Here in this article, you will get to know how tankless water heaters work, the main causes of ignition, and how you can overcome those problems. Read the article to find the answer to your questions and solution to your problems.

Common Causes For Ignition Failure

Well, behind every problem there are several reasons and once after knowing the reason behind the cause then you can take the next step to solve the problem. So, the basic common reasons behind the ignition issues that you should take into notice are as follows;

1. Electricity Problem

The first and the most common problem that is faced by tankless water heaters is when they are not working even after power outages due to electricity issues. The first thing you need to do is check the electricity voltage. Many models of tankless water heaters require electricity rather than gas, which means that proper voltage of electricity is necessary to run it properly.

Also, it consists of electronic panels, which show electronic ignition, error codes, and temperature gauges. So, if there is a problem with electricity then do check the circuit breaker to check if all parts are switched to on position. So if the circuit for the tankless water heater is off, before putting it on you have to turn off all the other appliances for safety measures.

2. System Overload

System overloading is another great factor that causes ignition failure. When your tankless water heater capacity is low and simultaneously you need hot water, as a result, the system overloads. If you are taking shower and at the same time another person wants to take shower then multiple hot water applications lead to ignition breakdown.

Low capacity tankless water heaters limit the demand for water for two or more purposes. In order to overcome this problem, you need to buy another good quality heater for yourself. Also, you need to reset the unit setting or buy the higher-level capacity system to prevent overloading and ignition problems.

3. Blockage In Air Supply

Another reason for tankless water heaters not working is that their air supply or exhaust is blocked, which leads to ignition problems. You get to know this problem when the error code is displayed, which shows that there is a problem in the combustion air or outage. Firstly, to make it correct you need to check the connections of all the pipes that either they are fixed properly or there is air leakage from the holes.

To prevent this problem you need to make sure that all the pipes are located outside your home where there is no blockage of air supply due to birds’ nests or wasps’ nests. Also, you should install the water pipe too closely so that the air from the pipe does not leak, which will lead to ignition issues and fire hazards.

4. Cold Water Sandwich

A cold water sandwich is a situation when one person from the family has taken a shower and now it’s your turn where you first feel the warm water and then it becomes cold in a few seconds again. When the water gets colder after a few seconds of getting hot water, this situation is basically termed a cold water sandwich. This situation occurs when there is a problem with the pipe.

The initial warm water is basically the trapped water in the pipe that you experience during the second shower. In this condition, the cold water is in between the water heater and the shower. For this condition, you need to wait a bit until the cold water passes from the pipe and you get the hot water in your shower again.

5. Dirty Electrodes

Another problem that causes the ignition problem is the dirty electrodes. To overcome this problem you need to clean the dirty electrodes. There is basically a white substance that is built upon it, which you need to remove. To work it efficiently you need to clear carbon from its brackets. While removing you need to clean it gently so that you do not damage it. You need to use 100 grit sandpaper for proper cleaning.

How a Tankless Water Heater Works

How Does a tankless water heater work

Now that we have known the reason behind the ignition failure of a tankless water heater, it is important to know how the device functions so that it becomes easy to detect where the problem is occurring. The tankless water heater heats the water instantly on your demand, which means that you just need to turn it on before you need the hot water. The heating process occurs when water passes the heat exchanger.

The heat exchange is basically the combustion chamber, which consists of the gas burner for the ignition process. The gas burner is placed below, which passes the gas through the gas line and gas valve. When the user needs hot water, the electronics in the unit react in order to allow ignition, which creates sparks and allows the chamber to ignite the burner. In this way, the running water becomes hot as you open the hot water tap.


Why is my tankless water heater not igniting?

There are many reasons for the tankless water heater not working. But, the most prominent and common reason is the low flame or burner. Low flame is basically because of the dirty or clogged inlet filter. You need to install the pipes properly so that the pipes do not overlap.

What maintenance is required on a tankless water heater?

Maintenance is necessary for any device as it prolongs its function and makes it durable. The tankless water heater maintenance requires proper flushing of the system at least once a year. Also, you need to clean out its filter, which needs to be cleaned regularly. Cleaning the water filter and tank also enhances its functioning life.

How long should a tankless water heater last?

A tankless water heater works efficiently as long as you properly maintain it. The durable gas-burning tankless water heaters last for almost 20 years or even more. Whereas the tankless electric heaters last for 7 to 8 years, which also depends upon their quality and maintenance.

How do you ignite a tankless water heater?

When you ignite a tankless water heater and it does not work properly, you need to shut off the valve and turn it on again. Also, you can restart the unit in order to function properly. Once after resetting the whole unit will start to work efficiently.

How do you test a tankless water heater igniter?

To test a tankless water heater igniter, you need to know where it is located. The ignition switch is located at the center of the heater where it is present to the left of the drain plug. To turn on the burner you need to lift up the power switch first and wait until the electric igniter sparks.


Well, I hope that this guide will make it easy to solve the problem of ignition failure. A tankless water heater works efficiently but if some problem occurs you can easily overcome those problems. The above list of problems is quite common but now you have got the idea so you can be aware of where the problem is lying. This guidance will solve all your problems regarding tankless water heaters.

With years of experience under his belt, Adam decided to put his water heater knowledge to work. By providing high-quality content and expert guides, Adam hopes to help anyone looking for expert water heater advice.