Explore the most common tankless water heater problems, reasons and symptoms. Learn how to fix the flame failure, fluctuation, not enough and no hot water, covering Rinnai, Takagi, Noritz, Bosch and other tankless models.
If you need any help for your water heater, contact a plumber here!
Modern and advanced tankless water heating systems are "smart"; they are able to control, monitor and adjust the operation, also performance and efficiency continuously. All the models are equipped with the electronic circuit board known as the electric boards that utilizes a computer chip to help in diagnosing a problem and displaying an error code.
The great thing about this advanced feature is that any issue or part failure that exist inside the tankless water heater will be shown as the error code or flashing light, on a display located at the front of the unit or screen of the remote controller (if applicable).
For example Noritz error codes will display: 11, 90, 99...
Bosch has these codes: A2, C1, E1, FA, 8E...
Rinnai error codes are shown as: 02, 10, 11, 52, LC...
Takagi: 121, 311, 321...
AO Smith has these error codes: 02, 10, 11, 12...
This is what helps in diagnosing the tankless water heater problems and successful troubleshooting. When these errors appear, call a qualified technician to service the unit or replace the faulty part.
Noritz, Rinnai, Takagi, Rhee, Bosch and other tankless manufacturers will approve the warranty if the problem occurred within the warranty period and only if the licensed technician performs a service.
If you require a professional to fix or install your tankless water heater, fill out the short form on this site and get connected with the local plumbers to get three free quotes.
No ignition
Flame failure
Overheating and thermal fuse failure
Temperature fluctuates
Water is not hot enough
Water is too hot
Other problems
Preventing problems
To review tankless water heater problems more efficiently, we will consider or assume that the water, electrical and gas lines and parts' installation are correctly done, and that unit was working good before the problem occurred.
I have seen many users complaining: "I don't have any hot water for my shower when I open the tap." And they call a technician, pay a lot because they didn't follow simple rules; to check is there a gas, water or electricity at all, sufficient water flow and other.
A burner does not ignite when the hot water tap is open.
Tankless water heaters use the temperature sensors to protect the heater from overheating and exceeding the maximum allowable temperature on the heat exchanger. Follow the list below to check, diagnose and troubleshoot tankless water heater problems with the symptoms mentioned above.
If the heater freezes during the cold winter days, the heat exchanger can burst. This is why electricity and gas have to be supplied so the freeze protection can be activated. Another solution can be to install the auto drain down solenoid valves.
If you experience low water flow or pressure you might have too many hot water applications running at the same time. The greater draw will result in an increased pressure drop. Another cause for low flow might be dirty cold water inlet screen.
For problems with and related to the pilot light check out the article why my pilot light goes out.
Regular annual inspection and periodic maintenance are imperative to keep your tankless water heater running and performing well. Water heating system and unit parts should be checked at least once a year to reduce the chances for tankless water heater problems.
Note: There are some prolonged activities done by the specific heater elements, like when the fan continues to run after you turn the hot water tap off. This is a regular occurrence, and it can last for a short period, to ensure that any residual products of combustion are vented out.
Another frequent complaint or "problem" which is normal among tankless is the white smoke coming out of the exhaust. This is typical during the cold weather, when the exhaust fume temperature is much hotter than the outside air, as the fume contains lots of water vapor and condenses.
It is also good to know that sometimes safety features will be triggered, and these are not something that will be considered as an issue. The unit will stop its operation in the next occasions:
Troubleshooting tankless water heaters
Comparing tankless
How to winterize tankless
Installing tankless
Benefits
Tankless maintenance
Tankless vs. tank-type