Amazing! And that info I had was given to me from a phone hotline worker at Pentair! Looks like more research to do. BTW, what exactly does the PHOSFREE or PHOS-X do to the phosphates in your pool? and why do they say it is important to keep the phosphates below 125ppm? You mean we can just ignore phosphates altogether and never need to worry about this..ever?
Rhonda, welcome to TFP
Allow me to answer the technical questions you have and clear up some of the misinformation you have been provided by that ever-so-helpful Pentair "tech"...
Phosphates are a nutrient needed by all living organisms for proper growth, biochemical regulation and reproduction. Without phosphates, life on earth would not exist. If you ever garden, any gardener can tell you that fertilizer always displays three numbers - nitrogen content (as urea and nitrates), phosphorous content (as phosphates) and potassium content (as potash). Those three components are absolutely essential for plant life. Algae, is a form of plant life and, as such, needs phosphorous in order to thrive and grow.
Phosphate removers are a chemical compound that reacts with the phosphate ion (PO4) in water. All commercial and retail phosphate removers use an inorganic salt called lanthanum chloride (LaCl3). The lanthanum chloride dissolves readily in pool water and dissociates into lanthanum ions (La3+) and chloride ions (Cl-). The lanthanum ions react with carbonate and phosphates in the water and forms insoluble precipitates of lanthanum carbonate and lanthanum phosphate. The lanthanum carbonate is also not stable chemically and will further react with phosphates transforming from lanthanum carbonate into lanthanum phosphate. As I said, these compounds are insoluble in water at typical pool water pH. So that is how phosphate removers work - they convert the dissolved phosphate ions into an insoluble salt that precipitates out of water.
Where the Pentair tech got it all wrong is in two areas - first, phosphates do not react with chlorine at all or to any degree that can be measured and have no direct effect on chlorine levels. Second, the insoluble phosphate salts created by products like PhosFree do not typically sink to the bottom of the pool but tend to remain suspended in solution making the water look cloudy. This is actually a desirable effect because you want your filter to be able to catch these suspended particles and filter them out. This is how, ultimately, the phosphates are removed - they transform into an insoluble, suspended compound that your filter then removes and you backwash away. Some of the remover products contain a clarifier as well as the lanthanum chloride in order for the clarifier to cause the lanthanum phosphate particles to stick together and form larger, easier to remove particulates. However, this is not always necessary and, depending on the filter type, a pool filter can usually clear the suspended solids within 24-48 hours. Sand filters do not filter fine particulate very well, so in those types of pools, using a clarifier with a phosphate remover can speed up the removal process. Cartridge and DE filters typically do not need clarifiers.
To first order, you do not need to focus on phosphates at all. A pool can be properly chlorinated and easily managed without ever having to treat for phosphates.