Water Heater Blog

Easy Fixes for Common Tankless Water Heater Issues

Nov 5, 2021 | Tankless Water Heaters

Having a tankless water heater in your home provides your family with maximum convenience while saving water and electricity. However, problems of all kinds can result in the malfunction or failure of this important appliance. 

To take full advantage of the benefits of a tankless water heater, it always pays to know the most common issues it can face and how to easily remedy them. Here are some problems you may encounter:

1. System Overload even with Tankless

Different brands and types of tankless water heaters have varying capacities, so it’s possible to encounter a system overload if you have one with relatively less capacity. This happens when multiple hot water applications are taking place at the same time, resulting in either shutdown or abnormal functioning of the heater. 

You can fix this by completely resetting the water heater unit. If you think this can happen again because of the number of people in your household, it’s best to upgrade to a heater with a higher capacity. 

2. Cold Water Sandwich Common in Tankless Heaters

The cold water sandwich, common in tankless water heaters, happens when hot water comes out, followed by a stream of cold water, before the temperature climbs up again, and so on. You probably experience this phenomenon every time you jump in the shower right after another person has finished.

The first hot gush of water comes as the leftover from the previous shower. Subsequent cold streams of “sandwiched” water are due to the distance that water has to travel from the heater proper to the showerhead. This is completely normal with any tankless water heater, and there is no need for you to worry. Just make sure to let any cold water pass if you really want to enjoy a full hot shower. 

3. Why Does my Water Heater have a Blocked Exhaust or Air Supply

To remedy this situation, check your vent pipes for leaks or holes and ensure they are correctly connected. Animal and insect nests can block these pipes, so make sure to check for these as well. Installing your tankless water heater near other objects can also potentially block the vents and make way for fire hazards. 

4. Flame Failure

Causes of flame failure include regulator problems, combustion issues, and many more. The best thing to do is get in touch with professional technical support for a possible water heater repair. 

5. Water Heater Ignition Failure

A water heater fails to ignite when there isn’t enough propane supply. Check for this first before examining other potential causes. 

You can then make sure that the gas and water valves are fully opened if there is no problem with the gas supply. Finally, contact professional personnel if the issue seems to be with another part of the system. 

6. Mineral Buildup in your Water Heater

Mineral buildup within tankless water heaters is a common problem for many homeowners. The high levels of two minerals, calcium and magnesium, in your water can cause scaly buildup and interfere with the normal functioning of the heater. 

To extend the lifespan of this equipment, make sure to regularly check for any burgeoning buildup and address it with the proper remedy. Always consult with a professional before flushing substances and using cleaning kits for your tankless water heater. 


As with any home appliance, the way to fully enjoy its benefits is to make sure it is properly used and maintained and to immediately address any issue that arises. Follow our tips above so you can relax in your next warm bath without a hitch.

If you are looking for water heater maintenance in Houston TX, reach out to Houston Water Heaters, the trusted expert in tankless water heater installation and repair. Call us today!

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