I have a serious problem with a newly constructed house for which there appears to be no answers forthcoming from the builder etc. There is a drainage leak inside a major support concrete beam (supporting the overhang of the upstairs section of a house which is all concrete block construction). 1/Is there any way to seal off this leak internally as to try and access this solid beam will involve a huge demolishment and a possible weakening of the whole support structure? 2/Is it possible, as the plumber has claimed, that the leak will eventually seal itself off as residue from soap etc collects on the inside of the PVC pipe? There is no calcium in the water supply (cistern water) so I cannot rely on this. The builder has gone bust and I am left holding the can on this one without a clue about what to do.