I got to admit actually i do use lime lite too, but hi phos is the kiddie....if scale is really bad and you want it gone instantly with no scrubbing i use sulphuric acid drain cleaner from staples........but again be bloody careful it will melt your skin or make you go blind if you get it in your eyes.........dont try to scrub with a brush either cos it will melt......but it is good and will remove limescale on contact. WEAR GOGGLES, GLOVES, CHAIN MAIL SUIT ETC ETC ETC DONT TAKE ANY CHANCES IT IS EVIL be extremely careful to ensure that no traces of it are left behind and make sure you are insured to use it.........