I assume you mean plastic systems?
Has to be water
I know polypipe call for a water test at 18bar for minimum of 15 min max a hour.
Cannot use air for H&S reasons.
Sorry for late reply. Thanks for advice. I know there’s one or two lads on our firm that have them. Always tested with water but sometimes I have to walk from one end of the site to the other for water and thought it would make it easier.