When we bought our present bungalow 18 years ago, all the floors had to come out due to Red Ash infil (failed sulphur test) The hardcore was replaced with MOT (stone to me!) and the floors all re-concreted/screeded.
Obviously we were not living there at the time!
However, all the heating pipes were buried in the floor originally, and are the same now.
During recent work, I had occasion to isolate the cold water feed to the storage tank and CH header tank in the loft, it was then that I noticed that the header was gradually emptying (down a couple of inches in about 4 hours). It's not rocket science to figure out that I have a leak, but having checked all over the house, there are no damp patches in the floors etc. - Is there any way of finding the leak? the pipes are about 2-3" down in the screed, I think (they were lagged with something similar to hessian with a clear plastic overwrap if memory serves correctly). Or, am I going to have to re-plumb the whole lot "on the surface"?
Advice welcomed