Early on in my plumbing life i fitted a bathroom for a friend. I failed to note that the pipework under the bath for the taps was in imperial 3/4". I fitted a pair of push fit flexies onto the 3/4" I had cut in readiness. The bath went in, then tiling, bog, handbasin, shower valve, all the stuff. When it was all done, everything fine; the shower was a manual mixer running off gravity (the bath cold was gravity off the header tank too) and it was a crap dribble as I told her it would be. After putting up with the crap shower for a few weeks she lobbied the landlord for a boiler change to a combi. you know where this is going?...... Big pressure increase to the bath taps and the shower valve tapped off the tap pipes. It lasted two days. While she was out the cold flexy blew off the 3/4" imperial copper(slightly smaller than 22mm). Result? One entirely flooded house. A small lake. Boating was possible. She took it all very well. Claimed on the insurance, got new everything upstairs and down, carpets, laminate, full re-paint. Delighted in the end. Even then, I didn't twig what had happened until a few days later when a plumbing mate pointed it all out. I have a 3/4"/22mm end feed adaptor in my toolbox now to prevent that happening again.