Very high water consumption

[JX350C]

This was a new build so possibly not installed correctly as the cold water supply to the HW cylinder was/is not from the balanced cold connection on the combination valve set, and the HW expansion valve may not have been set correctly to 6.0 bar or it was reduced to 3.5/4.0 bar, it certainly looks as if it wasn't commissioned properly, if at all, the mains PRV was fully opened with the stopcock left throttled in.

Yes I totally agree. I'm convinced this has been a problem since we moved in. We have written to the water company to see what they say.