Currently running a bunch of 22mm copper pipes through an awkward location. Difficult to get the torch to the joints, and very difficult to get to an earlier joint after more are done. So I'm air pressure testing as I go.
All well and good, everything passing first time. And then I and see the pressure gauge gently falling and can hear a very faint hiss.
Damn - have to slice up some pipework and do it again.
Except the hiss is coming from the plastic push fit stop end I'm using during pressure testing.
The copper pipe I'm using has a BS number very lightly stamped on it in regular spots - seems that one of those spots is just enough to allow a leak past plastic push fit.