PVC fittings are said to seal because their openings are tapered and the usual gluing technique fuses the pipe to the fitting. But how do PVC repair couplings ( e.g. https://www.lowes.com/pd/charlotte-p...E&gclsrc=aw.ds) seal? My understanding is that a repair coupling will temporarly slide completely over one pipe and then be slid back to overlap two pipes in order to hold the two pipes together. Does the usual gluing technique seal such a joint reliably?