How to troubleshoot a tankless water heater

June 24, 2025

How to troubleshoot a tankless water heater 


If you have a tankless water heater and you find that it’s not working, it can be frustrating. However, before you panic and call a professional, there are a few things you can check yourself. Here are some things to look out for if your tankless water heater is not working. 


Check the power source:

 The first thing to check when your tankless water heater is not working is the power source. Make sure the unit is plugged in or that the circuit breaker hasn’t been tripped. If it has, try resetting the breaker and see if that solves the issue. 


Check the gas supply:

 If your tankless water heater runs on gas, make sure the gas supply is turned on and the gas line is connected properly. If the gas supply is on and the unit still isn’t working, you may need to call a professional to check for any gas leaks or other issues. 


Check the water supply:

Make sure the water supply to the tankless water heater is turned on and that there are no blockages in the pipes. If the water supply is on and the unit still isn’t working, you may need to check the water filter for any clogs or damage. 


Check for error codes:

Many tankless water heaters have built-in error codes that will display on the unit’s screen if something is wrong. Check the owner’s manual for your specific unit to see what each error code means and how to troubleshoot it. 


Check the temperature settings:

If the water coming out of the unit is not hot enough, check the temperature settings on the unit. Some models allow you to adjust the temperature easily, while others may require a professional to adjust the settings. 


Check for mineral buildup:

If your area has hard water, it’s possible that mineral buildup could be causing your tankless water heater to malfunction. Check the unit’s manual for instructions on how to descale the unit and remove any mineral buildup. 


Call a professional:

If you’ve checked all of the above and your tankless water heater still isn’t working, it’s time to call a professional. A licensed plumber or HVAC technician can diagnose the problem and make any necessary repairs or replacements. 


In conclusion, if your tankless water heater is not working, don’t panic. Check the power source, gas supply, water supply, error codes, temperature settings, and for mineral buildup before calling a professional. Regular maintenance and inspections can also help prevent future issues with your tankless water heater. 


Frozen outdoor AC unit with ice covering coils and tubing.
February 17, 2026
Learn what to do if you have a frozen AC unit, and when you need to call in the professional HVAC technicians to ensure that your air conditioner is safe to run.
Two orange and white cats sleeping on a white radiator.
February 13, 2026
Gain expert insights and follow step-by-step instructions for safely and efficiently bleeding air from pipes in a boiler heating system, including radiators.
Man in blue uniform and cap working on HVAC system
February 9, 2026
Dive into a comprehensive comparison between Trane and Carrier, two leading brands in residential furnaces including Trane's durability and Carrier's advanced tech.
Carrier heat pump unit mounted on a grey pad against a grey house exterior
January 27, 2026
Compare the top 10 premium 20+ SEER2 rating heat pump brands for features, cold climate performance, energy savings, and reliability in Ohio and Michigan homes.
Diagram of a house with a ground source heat pump system with a horizontal ground loop.
January 21, 2026
A comprehensive comparison of geothermal heating systems and air source heat pumps for residential heating and cooling with a focus on the climate in OH and MI.
Grey York Residential furnace with white PVC pipes in a utility room in a home in Toledo, Ohio
January 16, 2026
Find out the top high-efficiency residential furnace brands, York, Rheem, Carrier and York, in this guide to help you choose the best residential HVAC system.
White wall-mounted tankless water heater in Toledo, Ohio for residential and commercial properties.
January 14, 2026
Explore the differences between tank and tankless water heaters for your Toledo, Ohio home while comparing features, benefits, lifespan, and overall costs.
Person in red overalls installing radiant floor heating tubes for a radiant floor heating system.
December 29, 2025
Discover the benefits of radiant heating for your home, including how it works, the types of systems available, and why it’s an energy-efficient heating solution.
HVAC units and toolbox next to a brick building. Air conditioning units in Toledo, OH
December 24, 2025
Discover effective tips to remove musty odours from your home, from quick fixes to long-term solutions for a fresher, healthier living space in your Toledo home.
Hand holding remote aimed at a white wall-mounted single-zone mini-split system in Toledo, Ohio
December 16, 2025
Find out the step-by-step process on how we install a mini-split single-zone system in Toledo, Ohio for heating and cooling systems for your home or office.
Show More

We're Listening | Get a free quote today!

Fry - Blog