Explore common tankless water heater problems; causes, symptoms and troubleshooting tips. See how to repair a tankless heater when there is no hot water, water is too hot, there is not enough hot water, the pressure is low, cold water sandwich (the temperature of water fluctuates: hot-cold-hot), the gas burner doesn’t ignite, and what to do if there is an error code.
If you are the owner of a "smart" tankless water heater from Rinnai, Noritz, Paloma, Bosch, Takagi or similar, this troubleshooting guide is for you. The guide deals with the most common problems and explains some of the error codes.
Tankless water heaters are durable and long lasting units that do not require much maintenance. They are expensive, efficient, environment-friendly, have the advanced technology, could display an error code, but can also fail and cost you a lot to fix.
One of the most frequent complaints I have seen in many reviews and forums, is: "I didn't get hot water instantly." Alternatively, it takes too long to get the hot water at the fixture.
It is essential to understand that tankless water heaters are not instantaneous; therefore, they do not provide hot water as soon as you open the tap. Only those tankless heaters equipped with the recirculation pump or the buffer tank are capable of delivering hot water super-fast. If this is what you need, buy Rinnai RUR98 or Navien.
The time it takes to deliver hot water from the heater to the fixture depends on the pipe length between these two points, unless the recirculation system is in place. Due to the long water pipes, cold water that resides inside must be pushed away before hot water reaches the fixture, affecting the comfort. This is not a "problem" so do not spend hours trying to find the solution or calling the “expert.”
"Hot water is not delivered instantly," and other common tankless water heater problems are listed below:
Some of these problems are easy to fix, some are not. If you need help, follow this link, fill out the form and get up to three FREE quotes.
The list of the error codes can be reached if following the provided links below.
Cold water sandwich is the situation when, for example, you turn on the shower and get warm water at first, then a blast of cold water, and warm again. If the water heater was used before your shower, some hot water remained from previous use – and that is what you felt.
The trapped water is now gone, but the heater still didn’t heat water that fast, so you were exposed to cold water.
The longer the pipes, further the water has to travel, more you will feel the gap.
Note: If the temperature of hot water fluctuates during the shower, for example, it is recommended to combine your tankless with the “buffer” mini tank. The mini tank will always have hot water ready and deliver it to the shower before the tankless warms up.
Most tankless water heaters are equipped with a diagnostic system that incorporate the microprocessor and LCD screen, which displays an error code if the problem occurs. An error code can appear due to many reasons, from a simple spider web and air/exhaust blockage to more serious gas or exhaust leak.
Use the following articles to get help on how to troubleshoot problems on Rinnai, AO Smith, Noritz and American.
Keep in mind that some unusual activities are normal; such as when the fan motor is still spinning after the water heating operation stopped. In this case, the fan motor runs for some time to force the exhaust gases out through the vent system.
Many tankless water heater problems are associated with the flow rate. For example; the water got cold during the shower because the flow from the tap was below the minimum. By keeping the flow rate above the minimum required, this and many other problems might be prevented or resolved.
Another "unusual activity" can be a white smoke that comes out of the exhaust vent, and can be seen during the cold weather, when the temperature of the exhaust gases is much higher than the temperature of the air.
Some problems are possible to fix only with the right tools and skills, so to keep the warranty valid and unit functional, it is at your best interest to contact a professional plumber.
Please describe the problem in details including the type of water heater and brand/model.
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