How to Troubleshoot a Tankless Water Heater

November 12, 2025

Tankless Hot Water Heater Troubleshooting Guide 

One of the best inventions of the last hundred years might be the tankless water heater. Okay, that might be a stretch, but the tankless water heater is truly amazing. We absolutely love installing, repairing, and servicing these great machines. Whether you are looking to free up space in your maintenance room or simply want a more efficient water heater for your home, a tankless water heater might be the solution for you. However, with new technology comes a lot of questions about how to service a tankless water heater, and whether there are any troubleshooting steps that a client can take before calling in our expert plumbers. You're in luck, as we've decided it's time to educate our clients on some of the best troubleshooting options available to help you determine if you can fix your tankless water heater yourself. 

 

Initial Troubleshooting (Any Owner)

Tankless water heaters are not the most complex pieces of equipment and are generally going to be able to be troubleshooted by any owner for minor issues. The first step you will want to take is to check the power and determine if you are dealing with a blown fuse or if the unit has power. If that is not the issue, you will need to check if the gas line is open and if the supply is still full when running the heater on propane or another stored gas. If it is not electrical, or gas-related you can then look to see if there is an error code and what the common fixes are for your specific unit.

 

Common Fixes 

For most tankless water heaters, the fixes to almost any problem can be quite simple. Here are a few of the most common issues, and how to fix them.


Reset the Unit

Yes, the old 'turn it on and off again' method works quite well for these units, and you would be surprised at how many times it can resolve error codes. Just like a computer, tankless water heaters sometimes need to turn off to work again, and a simple reset can prevent a lot of the call-outs we end up getting here in Toledo, OH. 

 

Check for Blockages

If a reset does not work, you will then need to check for blockages within the system. Start with the vents and inspect the exhaust and air intake vents to see if anything is stopping airflow to and from the unit. Next, check the water inlet filter at the front of the unit to see if it is clogged and needs cleaning. 

 

Low Flow Issues

If you are experiencing low flow issues from your tank, the problem may be specific to a particular fixture, rather than the unit itself. Test all of your fixtures, and if you're experiencing low flow from a specific fixture, clean the mineral buildup in its filter and check for any debris or constrictions in the water line leading up to it. 

 

Temperature Issues 

If you are dealing with water that is too cold or too hot, then you might want to check the control panel to see if something has been reset. However, remember that a higher temperature setting can reduce the overall hot water flow rate to all fixtures. 

 

Advanced Troubleshooting (Confident Owners)

Clean the Igniter and Flame Rods

If you are feeling up to it and your hot water unit is not igniting, you can also clean your igniter or flame rods with a soft cloth or fine-grit sandpaper. This will allow the unit to start up more easily. However, be careful not to damage any of the ceramic parts. 

 

Check the Internal Fuse 

If your unit is not responding at all, you could be dealing with a blown internal fuse. For most, this is best left to a professional; however, you can power down the unit and check the fuse to see if it is tripped. 

 

What to Do When Troubleshooting Does Not Work

If you fall short in your troubleshooting and are unsure what to do next, you should call Fry. We have been repairing and servicing tankless water heaters for decades, and can provide you with a service that will get your unit back up and running in no time. 


When to Call in the Professionals

There are a few situations where you will want to call in the professionals before trying to troubleshoot. First and foremost, if you believe the issue could be gas or electrical related, you will want to call in a professional plumber to inspect it. As well, if you are dealing with an internal component failure, such as a control board or an internal fuse, you will want to call in Fry to do the work to keep your warranty up to date. 



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