Calcium phosphate scale is a new problem creeping into the swimming pool and hot tub industry. However, the problem has long been recognized in the boiler industry. Calcium phosphate scale became prevalent when reverse osmosis (RO) technology was widely applied to municipal waste water. Due to recent water shortages, municipal waste water recycling and reuse has become a major area where this water purification technology has become prevalent. As such, preventative actions have become commonplace for commercial boiler water and now, it seems, it may become standard for treating swimming pool and hot tub water, as well.