I had closed the isolation valve to my outdoor tap a few weeks ago because of the freezing weather and re-opened it today. The compression fitting burst open. I used a Speedfit pipe with an insert to connect to the isolation valve. The pipe just slipped out of the compression nut, leaving olive and insert inside. I tried to fit the olive back on the pipe to redo the fitting but the olive was too small. Wouldn't that mean the olive was sufficiently compressed originally? The same thing happened previously with another isolation valve nearby but in that case, it had been a plumber who had fitted it. At that time I thought he had not inserted the pipe deep enough and tightened it sufficiently, which is why I was careful to do so myself later. Why would the pipe come off? The connection is close to the main water feed, so pressure would be quite high but I don't see why a compression fitting can't handle it. Are copper pipes a better choice for a compression fitting? How to ensure the same thing doesn't happen again, especially when I'm not around?