DownWest
Well-Known Member
I lived in a very hard water area and used Vaillant heaters for house hot water. The small bore tubes in the heating matrix used to calc up ate regular intervals and had to be cleaned out with acid. There appeared to be flow, but not enough to get the gas flow up to a decent flame. This doesn't sound like the OPs problem, as he has a good flame, but it is worth keeping in the back of ones mind for future ref.