5 Common Tankless Water Heater Issues and How to Solve Them

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Like any other appliances, tankless water heaters come with their own pros and cons. Opting for a tankless heater over a traditional one is a space-saving option for your property that also has the potential to lower your utility bills and provide you with endless hot water. However, you may encounter certain issues even with the best gas water heater you can get, such as those related to wear or extensive usage.

In order to ensure that its benefits won’t be undermined, it is essential to learn more about the most common tankless water heater issues in advance to be able to solve or avoid them altogether. Apart from overloading and mineral buildup, the most common problems include corrosion, the “cold water sandwich” effect, and restricted energy supply. Continue reading to learn more about maintaining your tankless water heater to avoid these issues.


Corrosion is the most common problem people experience with their tankless water heaters. It is caused by the lack of water flow through the water heater and can be easily prevented by using a water filter. Most water filters are designed to take the place of a traditional water softener, which means that they can remove minerals and other dissolved impurities from the water. This will help to prevent corrosion.

How to prevent corrosion: If you buy a tankless water heater, it’s a good idea to install a compatible water filter as well. This will reduce the chances of corrosion and ensure that your tankless heater will work as intended for years to come.

Mineral Buildup

Mineral buildup is another problem reported by many owners of tankless water heaters. Over time, constant use of the tankless heater causes mineral deposits to build up inside, which in turn causes the heater to fail. This can be avoided by treating your water with a water softener or a water filter before using it in the tankless heater.

How to prevent mineral buildup: The best way to avoid this issue is to use a water softener. If you have a tankless water heater and use hard water, it is recommended that you connect it to a water softener. This will help prevent the formation of mineral deposits inside the tankless heater and also save you money as you can use less water in your tankless heater.

Cold Water Sandwich Effect

The cold water sandwich effect is another common problem with tankless water heaters. It occurs when the water that runs through the heater is warm, but the cold water entering from the faucet is cooler than the hot water on its way out of the heater. This causes the heater to cycle on and off frequently, which can be irritating.

How to prevent the cold water sandwich effect: To avoid this issue, you will need to adjust your tankless water heater’s thermostat so that it doesn’t respond to “shorter” cycles. It is also recommended that you install a separate hot water line to your sink in order to improve the hot water delivery.

Restricted Energy Supply

Restricted energy supply refers to a situation where homeowners report that their tankless water heater works properly for a few minutes but then stops working due to a lack of energy. In some cases, this can happen after a power outage hits the house or during a power surge. This can cause frustration among homeowners as they must wait for several minutes before their tankless heater starts working again.

How to prevent restricted energy supply: To solve this issue, you will have to check your tankless water heater’s circuit breaker. If it is set too high, it can cause the tankless heater to stop delivering water when there is an energy shortage. 

In some cases, it is also recommended that you buy a surge protector for your tankless heater. This can help protect your tankless heater from power surges and power outages and can save you from having to reset it after each outage.


Overload can occur when a tankless water heater is used to heat larger amounts of water than it was designed to do. This may be because the hot water usage in the home has increased over time or because the tankless heater is not compatible with the household’s needs.

How to prevent overload: One way to avoid this issue is to upgrade your hot water system if necessary. You can also consider installing a tankless water heater with a larger capacity, which can heat more water at once.


Tankless water heaters have many advantages over traditional water heaters. These include lower energy usage and the ability to provide hot water at any time. However, there are various problems that can occur when you use a tankless water heater. Corrosion, mineral buildup, the “cold water sandwich” effect, restricted energy supply, overload, and the need for replacement parts are some of the most common issues reported by homeowners. To avoid these problems, you will need to regularly check your tankless water heater and follow maintenance guidelines as recommended by manufacturers.