A few years ago I had to do a very difficult new pipework job over an upper loft coming from a new Stuart & Turner 3bar pump to supply 3 showers. Customer is a very clever bloke and although he knew I use copper, said I could use plastic as it would be much easier. I refused and he then agreed, saying if a plastic fitting blew off on the hot side - the pump would pump hot water out at 3bar on 22mm and bring every ceiling below it down.