So I've got iron stains. I am purchasing "Pool Mate Mineral Out and Stain Remover" from Amazon. Instructions say that I should let the chlorine levels fall to ZERO so I have the pool running during the day, the chlorinator in the off position and the slide running water to help. I had shocked the pool so chlorine levels are high. How long do you peoples think till the chlorine drops to zero? What can I do to speed it along? Thanks!!