we had a new shower 2yrs ago ,got it treated with one of the products barrie mentioned,clearshield from memory?The bloke gave us intructions after showering,rinse it,wet wipe with a flannel,dry wipe with a micro fibre cloth.may sound alot but is pretty easy and I have done this since...result is the shower looks sparkling and new after 2yrs,I am just a bloke and the only ones that don`t do this are my daughters who know it peeves me off to not do it.Thankgod they don`t live here anymore.