Hep 2 O failure

Vibration maybe? - if taps are turned on or off very quickly and the pipes aren't clipped, they can make one hell of a bang.

Did it have a 'star' washer in the fitting that bites into the pipe?

If so were there any tell-tale marks on the copper pipe to indicate the washer had been pushed on properly?

cheers, Pete.

Assuming the threads on the cap hadn't jumped the threads on the fitting body then presumably it had unscrewed itself. For which I guess it must have been partly unscrewed to start with. I notice Speedfit has a sort of notch - extra resistance - you've got to get past when unscrewing it before you can undo it all the way.

No marks, but the star washer (grab ring) wouldn't move up or down the copper pipe at all.

Pretty much what I'm thinking. Can't see the cap had jumped the threads, my thoughts are that it wasn't tightened in the first place.

Suppose it might have been that. The nailed in clip had come adrift - I re fixed it with a screw.

Yes - had one failure of this type in our last house, where the central heating had been extensively re-worked with Hep2O. Caught it as it started to leak rather than gush, but it inevitably was in the most inaccessible place.... Cap was almost all unscrewed, and about to fall off. Failure was about four years after installation.

This type of fitting is normally supplied with the caps tight, so I suspect that this one was slightly lose on arrival, and I hadn't noticed. As this was for central heating the water hammer theory is not appropriate, so possibly pump/water vibration over a long period caused the unscrewing? Since then I now check all the nuts are tight on Hep before fitting.

However, in our current house I've been using Speedfit, as this now has caps that can't easily be unscrewed on arrival (as John notes), and have a further locking turn for final assembly.

Despite all this I am still a fan of plastic plumbing!

Charles F

You just called on Dr Drivel?

Are you sure it was a town house and not a high rise?

You should have replaced the Tee with a brass compassion tee.

It's good to hear that plumbing components care so much....