whats the craic.
sorry pal but never heard of a z dimension.{whats this}
in irelnd we start at half inch gun barrel {mild steel}up to 10 inch or more for industrial work. our copper then is half inch. 14.7 , with the uk comparison being 15 mm.
may i ask why u ask such a strange question.
some small technical things are never of any use to u once your at it for awhile.most lads forget more of these things than they remember. these things can be found in starting out plumbing books. maybe a trip to the library might be the job.best of luck pal