It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Ed Sirett
saying something like:

Dead on 22mm, measured with verniers. As the pipe was painted above
floor level, I had assumed it was copper until I pulled up the floor
boards and saw it was actually black plastic. A google revealed a couple
of threads suggesting this stuff is very thick walled, so I not sure it
does need an insert, or if a standard 22m olive will do the job.

The really thick-walled 22mm stuff can be used with an olive and no
insert... I have one outside that's being resisting mains pressures of
up to 10bar for 6 years.
--

Dave