Colton Deck

By: Colton Deck on February 21st, 2023

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Top 5 Most Common Takagi Tankless Water Heater Error Codes and How to Fix Them

Tankless Water Heaters

Takagi tankless water heaters are one of the top brands in the industry, but that doesn’t mean you won’t run into an issue or two owning one. Error codes are common with tankless water heaters in Southern California, but each one requires a specific fix that will almost certainly require the help of a professional. 

After over 15 years of servicing and installing tankless water heaters, we’ve seen it all. We've diagnosed and addressed countless error codes, from circuit board failure to clogged exhaust vents and pinhole leaks in heat exchangers. 

In this article, we’ll walk you through the most common Takagi tankless water heater error codes our technicians have encountered over the years. We’ll also touch on how each error code is fixed, so you can better understand what to expect when calling a technician for help. 

Let’s start out with one of the most common error codes that is easily fixed. 


Most Common Takagi Tankless Water Heater Error Codes


Error Code 991

This error code is categorized as a maintenance code. If you see error code 991, it means there’s likely a dirty fan or dirty gas manifold. A dirty tankless water heater means lesser efficiency, a greater chance for early breakdown, and a lower lifespan in general. 


Next Steps

If you see this code, you’ll want to call a technician as soon as possible. The technician will perform an inspection and determine the root of the issue. Once found, your technician will perform standard maintenance and cleaning. 

Your technician will also clear out any blockages in your system and ensure that there are no other issues in your great plumbing system contributing to the error code popping up. 


Error Code 711

Error code 711 is more severe than error code 991. This error code means there is an issue with the thermal fuse, which means you can bank on your tankless water heater’s heat exchanger needing some TLC. 

This error code can be caused by a lack of maintenance that causes the heat exchanger to overheat, breaking the thermal fuse. Unlike a maintenance code, you need to act on this error code immediately. 


Next Steps

Unfortunately, there’s no simple fix for this error code. Your technician will most likely recommend a heat exchanger replacement. Along with recommending a replacement heat exchanger, your technician should also inform you of the benefits of regular maintenance. 

Having regular maintenance performed every year will keep your heat exchanger in top shape, effectively preventing major error codes like 711 from popping up in the future. 


Error Code 111

If you run into error code 111, it means your Takagi tankless water heater is experiencing ignition failure. This basically means that the burner cannot light, which could be linked to a couple of different issues. 

Error code 111 can be triggered by not providing the gas supply or gas valve an adequate amount of gas. It’s also possible that your Takagi has a bad igniter or a blown fuse. 


Next Steps 

After calling a technician to your home, they will assess the tankless water heater to determine the cause of the issue. Once identified, they will take the proper steps to resolve the issue, whether it's the gas supply, circuit board, or other root cause. 

Along with addressing the cause of error code 111, your technician will also recommend routine maintenance to prevent other issues from cropping up in the near future. 


Error Code 441

This error code signals an issue with the flow sensor. You’ll run into this issue when the pre-filter becomes clogged and doesn’t allow enough flow for the tankless water heater to kick on.

The issue has less to do with your flow sensor in most cases and more to do with debris buildup somewhere in your system. This means that even something as simple as a dirty aerator on your kitchen sink faucet could cause this error code to trigger. 


Next Steps

Once you’ve requested a technician come out to your home, they’ll evaluate your tankless water heater and plumbing system to pinpoint the issue. This evaluation includes checking aerators on fixtures, the water supply, clearing any blockages, and checking your Takagi tankless water heater’s heat exchanger for excess scale. 

Once your technician locates the problem, it will be addressed with repair, rebuild, and/or maintenance. 


Error Code 101

This last one is pretty severe since it could put your family in danger. If you see this error code, it means the Takagi tankless water heater is experiencing improper combustion. The danger here comes from the chance of a blockage in the exhaust introducing carbon monoxide into your home. 

In most cases, this error code is caused by a blockage in the intake or exhaust. Blockages can cause an improper mix of gas and air, leading to the error code displaying. 


Next Steps

Your technician will perform an inspection and clear any blockages found in the intake or exhaust. In most cases, this will do the trick. It’s a relatively simple fix for a potentially dangerous problem. 


In the Know with Takagi Tankless Water Heater Error Codes

We’ve touched on the most common Takagi tankless water heater error codes our technicians run into while out in the field. Now, you can feel confident about your next steps when any of these error codes pop up. 

It’s been over 15 years since we began working with tankless water heaters, and 13 of those years have been spent being partnered with Takagi. We understand these tankless water heaters inside and out, giving us a deep knowledge base of how to resolve these error codes. 

If you’ve been experiencing error codes on your Takagi tankless water heater and want some answers, visit our tankless water heater service page or click one of the below buttons to schedule a consultation or maintenance service.

If you inherited a tankless water heater in a recent home purchase or are just curious to know more about them, download our Ultimate Guide to Tankless Water Heaters to learn more about your investment. For those who are interested in preventing error codes from the start, it’s worth educating yourself on the types of maintenance a tankless water heater needs. 

You can also check out our full review of Takagi as a brand to get a better idea of where your tankless water heater sits compared to others.