How to Clean Your Tankless Heater


Tankless hot water heaters are a great investment of modern technology for your home – but it’s important to note that these things need cleaning maintenance to keep running in top shape. This is absolutely necessary to keep it running, especially for a long time, simply due to the fact of hard water and scale buildup that happens otherwise it will cause it to burn out. Consider having a tankless unit that lasts 2x longer that you’re able to maintain (not to mention 30% more efficient too) vs. a tank style heater that you’re unable to clean and eventually burns out from buildup on the elements.

It’s recommended to flush and clean your hot water heater at least once a year, and more often if the water in your area/home is particularly hard (two or three times a year). You should definitely make a habit of checking if there is any buildup monthly or every other month so you can know when to clean it accordingly – this keeps it running like new and more importantly makes it LAST. You don’t want to leave it and end up burning it out from mineral build up like a traditional tank heater – with a tankless water heater you have the ability and advantage of being able to clean it regularly so it has a longer life, which is the reason most people buy one in the first place!

Note: check the manual that comes with your SPECIFIC unit, as there may be special or specific instructions you need to follow.


Note: use vinegar ONLY, it’s just as effective as commercial cleaners without the chemicals – your homes drinking, cooking, and bathing water runs through your tankless heater, you don’t want chemical or harsh cleaner residue that might remain, even after flushing.


The following are general steps to clean and flush your tankless water heater:

  1. shut off the power/firing source
  2. turn off the main gas or propane feeding the unit, or if it’s an electric type unit turn off the circuit breaker
  3. close the water valves that feed into the unit, and close the valves that carry water out into the home – this isolates the unit so it can be cleaned properly
  4. remove purge port valve caps from the purge valves on each side of the cold and hot water valves – this relieves any built up pressure in the unit
  5. attach hose lines to the valves that were shut off that run into and out of the unit
  6. you may need a small pump (a basic sump or pond pump) to pump water into and out of the pump to flush it
  7. open purge port valves of hot and cold valves
  8. use 2-3 gallons of straight (undiluted) white vinegar as a cleaning agent, as you run and flush it out it may be full of sediment/debris so you may need to dump your bucket and get more fresh clean vinegar to finish cleaning your tankless heater
  9. follow instructions in your unit manual for specific instructions for recommended flushing procedure.
  10. when done, close purge port valves
  11. take off the hose lines from each valve that was used to clean the unit
  12. put purge port valve caps back on
  13. restart unit (refer to manual)
  14. run a tap in the house to get the hot water going again and the air out of the system