Wonderful explanation! I have a question, you said 1/4 gal. per 10,000 gal. for treatment. How much will that lower your PH? Is there a good "rule of thumb"? Mine is at 8.2 right now. How much should I add to get to 7.5? The following numbers are from the pool store's testing: CYA- 120, TC-10, FC-10, PH-8.2, Total Alk-178, Adj Total Alk-142, Total Hardness-261,TDS-400. I have a 26,500 gal IG with TA-60 sand filter, Hayward 3/4 Hp pump. Also should receive my K-2006 and K-1000 any day so I can do the tests myself. I went through several pages of posts to see if anyone has already answered this, but stopped after 6-7 pages. I am new to the site, and my search method needs help. Also, my water is dirty and slightly green. We vacuumed it, but I think I made a mistake and vacuumed to filter instead of to waste, and it just returned to the pool. While there for testing, the guy at the pool store talked me into buying some snake oil called flocculant. It is BioGuard Powerfloc. He did a cool demo, and it worked like a champ. I wanted to know what you guys thought before using it, or should I not? It seems everything has some sort of undesired ingredient in it. Thank you for your help!