Shower Door Water Spots

I had this in a house once and used laundry pre-soak stuff - don't remember what brand to get it removed - took a long time. I read a hint that I've used now that was to use shampoo - a cheap clear one is White Rain. The shampoo cuts thru soap scum very well and leaves the acrylic and glass shining. If you have a build-up, it will probably work, but I don't know how many scrubbings it may take. Then use the squeegee, every times - we do and our shower looks like new.