I think I've cocked up! I have installed a shower pump however the outlet valve of the pump is leaking. It connects to a copper pipe via a plastic nut and olive and I think I have overtightened this causing the valve to distort. I have bought a new nut and olive and tried fitting a new copper pipe but it leaks constantly. I have tried PFTE tape but this doesnt seem to do the job. Any ideas other than a new pump.