I once had the Leslie kid behind the counter SWEAR to me that if I did not buy PhosFree and get my phosphates below 100ppb (in case anyone cares, it's measured in parts per billion) that it would void my Pentair warranty on my DE filter
I laughed at him to his face and told him, "nice try kid, is that what they teach you to say?" I then proceeded to tell him that the exact opposite is true as stated by my pool builder who is a Pentair rep. Use of any phosphate reducers, coagulants or flocculent that will get imbedded in the filter medium will render the warranty void. The kid just shut up and immediately went after another customer after I schooled him.
Moral - You, the pool owner, are just considered an easy mark by pool stores to make money off of. They do not care one bit about your pool.
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