I am so thrilled to have found this forum...New pool owner of 3 months and my confidence is growing daily. I'm testing like a champion with a good kit and my numbers are all exactly where they should be. (Patting my own back as I type. BUT, two weeks ago, I took a water sample to Lesley's and my phosphates tested at 2500 ppb. They sold me a $80 bottle of liquid that our filter pressure detested. We cleaned the filter (cartridge) and were back in business. Fast forward to today: I wanted to see if Lesley's test numbers matched mine. They did, but again - Phosphate fear! 400 ppb. This time I refused the PhosFree and left with my $80 intact! Thanks to YOU, fine people!