Looking for advice / comments as the plumber who installed isn't very interested in addressing...
- my Navien whistles loudly especially when hot only is turned on. Plumber says gas company should come out and test pressure. There is a regulator on propane tank, then at house, then just inches before Navien. Maybe this is the issue.

But I am suspicious the issue is something else. For example, this unit is in an island cabin, winterized last two years, including fully drained. Unit did not whistle the first summer of use (unit has only been used two years so far, I would say 8-9 months total, but not even daily so likely 100 - 120 days of use). One thing I just noticed in manual is: condensation trap should be filled before use. This was never done after first winterization.

Thoughts / suggestions from your experience? Thank you very much!!!

the first thing i would try is flushing the unit.

lots of google videos on how to do this..

Thank you, good advice. Somehow the installer did not put flush valves on the in/out piping. Need to get this addressed.



Edited 1 times.

WOW... those are important. the unit should be flushed once a year.