It looks like I will have to run a waste pipe possibly behind a radiator or at least behind the 15mm feed pipes. To avoid sagging or distortion I am considering transitioning to copper pipe in the vicinity of the radiator. Would McAlpine compression fittings be able to join push fit PVC (nominally
41mm OD) to 42mm copper? I have found them quite suitable when transitioning from push fit to solvent weld but this will be to a slightly larger diameter.
Richard