Interesting subject..I was using alkathene,which we use as a water pipe,30mm OD,3mm wall thickness,screw together fittings,the same as plumbers use,was told its a good cheaper alternative to galv pipe..It is,,works great,and easy to set up and dismantle,has a variety of fittings for water traps etc,handles 150psi,worked for me at the last shop,havent installed it here yet,as I only have 75 square metres here.