I have Nortiz Tank less HW system in my house till recently I had good HW pressure, Now when I turn on more than 1 facet have little to no pressure.

I am on a private well who water is little hard and I do get calcium build up on the show heads and the tiles and the toilets do show the brown / orange stains

Today I cleaned out the strainer on the cold water inlet to the unit hoping that would be my problem but it was not.

I am suspecting the heat exchanger needs to be flused and cleaned out with like CDR or something like that to de-scale it.

Am I on the right lines or completely off base?

any ideas or feedback would be greatly appreciated