Burga007 .. yes broadly speaking in agreement with justlead1 based on 30m of copper service pipe with no allowance for fittings or valves etc. if the service pipe is poly then a different story as the diameter is smaller .. so would come down to about .54 l/sec. from a design point of view a normal house/flat/apartment with one bath & ensuite would have a probable simultaneous flow of .59 l/sec so the poly service pipe would be borderline. depending on the layout and size of property and potential for extentions etc I would probably go up a size even on the copper and maybe to 32mm on the poly.