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The Common Problems of Tankless Water Heaters and How to Deal with Them

| Wednesday March 29, 2023

The popularity of tankless instant water heaters has increased in the past decade as more individuals see the benefits of having one despite the high upfront costs. It can provide an on-demand warm water supply, which is ideal for those who want greater convenience. And, with further technological advancements in the past decade, instant water heaters are now considered the best warm water solution for countless households worldwide.


But despite being a cutting-edge innovation in the water heater market, tankless heaters still have problems that homeowners might encounter from time to time. Like other electrical appliances, a tankless shower heater may face issues during operation, especially in properties with high warm water demand. Below are some of the most common instant heater problems to give you an idea of how to deal with them.


The Cold-water Sandwich Phenomena


Even though the term “cold-water sandwich” isn’t that common in many households, quite a few individuals know of this phenomenon. This is when you experience a cold-water gap when using your water heater for showering or dishwashing. This usually happens when you use the heater connected to the shower or sink right after another resident uses it. You will see that the flow will start with hot water, which turns cold briefly before returning to being warm.


A “cold-water sandwich” usually occurs because warm water is trapped inside the pipes after you turn off the water heater. It takes a few seconds for the heater to supply heated water, so cold water follows the trapped hot water in the pipes. While this occurrence is not considered an issue for many, it can still be annoying for some. If you think this is a problem, let the shower or sink faucet run for at least 30 seconds before using it to ensure that you’ll only enjoy warm water during your showers.



Lower Capacity


Another potential problem users may experience with tankless heaters is that homeowners tend to overload their instant water heaters. Doing so can significantly decrease a heater’s capacity to supply warm water, especially if it is connected to various water points. This is especially true for those who have small tankless heaters and use them simultaneously for different activities.


To prevent this, it is ideal to look at your unit’s flow rate capacity to plan how to use the heater for different activities. As much as possible, try to avoid doing two activities that require heated water simultaneously, such as dishwashing and laundry. This can ensure that your heater will perform as expected and will not eventually shut down due to a high work rate.



Sediment Buildup


Even though instant water heating solutions do not store warm water, there is still a high possibility that the minerals from the water will accumulate in the unit’s interior pipes. This especially happens for households in areas with a hard water supply, which is high in minerals like calcium and magnesium. If left unattended, the buildup might get more extensive and block the pipes, resulting in the heater needing to work harder than usual to supply the property’s hot water demand.


An ideal way to deal with this is to make flushing a regular part of your yearly maintenance. This can help eliminate the mineral collection in the pipes, mitigating the risk of corrosion and leaks. Alternatively, you can install a water softener system that helps pull out minerals from the water before it reaches the water heater.



Ignition Failure


Another typical issue for tankless heaters, primarily those that run on gas, is a faulty ignition system due to damage to the gas line. The main symptom of this is an inconsistent warm water temperature, where the water does not heat up in some cases. This will significantly affect the heater’s performance, resulting in possible costly repairs if left unchecked.


You can check for this by seeing if the propane tank is already low or your gas supply is disconnected. If not, it could be that the gas valves are partially closed, so opening them can be a quick solution. But remember that working with gas appliances is risky, so if there are issues with the gas line, it’s better to contact a professional to help you manage it.





Tankless water heaters are an excellent option for homeowners looking for an energy-efficient and space-saving way to heat their water. However, tankless water heaters can develop problems over time, like any equipment. By being aware of the common issues and how to deal with them, homeowners can keep their tankless water heaters running smoothly for many years.


And if you are looking for the best bathroom heater in the market, why not choose Rheem? With almost 100 years in the water heating industry, Rheem has constantly focused on innovating and creating more advanced, high-quality, and intuitive water heating solutions to suit our customer’s unique needs. With Rheem, you can enjoy reliability, durability, and functionality.


Browse our extensive range of water heaters and learn more about the types of water heaters Rheem Philippines has available on our website. For any inquiries or more information about our products, you can also talk to one of our representatives by clicking here.

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