navien tankless water heater

Hi, I need a sanity check please. Developed a pinhole leak in a watts etx-30 expansion tank, about a year old. Contractor is coming back today to replace it. Googling the model, it appears this is a non-potable unit. However, it's been installed on a branch of the cold water line that...

I have a Navien tankless water heater – NPE210A. Two weeks ago, the hot water started turning colder after one of two minutes in the shower. Navien’s support had me troubleshoot the issue as follows: 1. Turn the unit off. 2. Close the isolation valves to the cold-supply and...