Following the enquiry here about a leaking pipe I asked the leading expert in the UK, who happens to be a friend of mine.
Dear Bill,
Plastic pipes generally don?t develop pinhole leaks (unlike copper pipes!) The most likely cause would be an external axial score on the outside surface of the plastic pipe which, if connected into a push-fit joint containing a rubber ?O?-ring seal, could eventually result in leakage from the joint in the form of a fine spray. This is obviously hypothetical, as I don?t know what joints were in use etc. If the piece of failed pipe is available for examination, I could arrange to have it examined to try and determine the cause of the reported failure.
Please let me know if you need any additional information.
Bill