Hi, you said you were putting in 4 or 4 showers, make sure you have enough water tanks to support this kind of undertaking, if they are power showers you will drain the tanks in minutes espesically if all showers are going at the same time,there is a limit to the amount of electric showers you can have on your fuse board, if its gravity fed showers make sure you have great head height otherwise the pressure will be greatly decreased, and you know women, if the hair is not washed properly they through a wobbler.hope this helps,let me know how you get on.
Kindest Regards
Dr Kevin