I'm trying to join a pipe to a pvc connector, I got one from the hardware store that seemed to match in size perfectly, but when I tried to screw it on, the thread seemed to not match, are there two 'threads' for pvc connectors, here's a picture of the sort of connector I'm using. Is it a metric / imperial thing?

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  • Pressure pipe or drain pipe? Drain compression fittings look a bit like unions, but are not. – Ecnerwal Dec 24 '17 at 17:44
  • Definitely pressure fittings (rubber rings etc clearly built for pressure). – Chris Pugmire Dec 25 '17 at 20:24

The threads at the union nut are not standardized, each manufacturer is likely to have their own thread. In fact, I suspect they deliberately use proprietary threads to force you back to their brand.

It is not at all uncommon for you to have to cut back and couple in an entirely new union.

  • Union threads are not meant to nor have they ever been designed to couple with standard pipe threads. It's like apples and oranges! Pipe threads go the pipe threads, union threads go with u...no they go only with their mate. – Paul Logan Dec 24 '17 at 20:34

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