When taking a water sample from a chlorinated water supply for bacterial analysis the sterile bottles normally contain a crystal of sodium thiosulphate which imediately neutralizes the disinfection effects of the chlorine and its products so that any still viable bacteria can be cultured in the lab. This is the ingredient in the water conditioner. I note what has been said about the pristene water supply of the greater Auckland region but any water drawn from an open water course, catchment or lake is likely to contain a reasonable amount of organic matter and therefore to produce chloramines which can realy only be got rid of with water conditioner.