Still new at this so please be nice. I have the TF100 test kit and my water is absolutely beautiful. One issue I just ran into in the last week. I noticed this week that all of the sudden I was getting a white ring around the tiles and on the rock waterfall. I haven't run a full test in about two to three weeks, but I do test at least every other day for PH and Chlorine. My PH has been staying around 7.6 when testing it and not changing. I added 20 oz of muriatic acid according to the pool calculator to bring it down to the 7.2 level. I tested again after waiting about an hour and my reading was the same. I added more muriatic acid, waited and it finally brought the level down to around 7.4. I then added what the pool calculator said to bring it down to 7.2 and it accurately did so. So my question is why when testing did my PH read 7.6 but it took almost 40 oz of muriatic acid to bring down? Do I just try to maintain my PH at 7.2 to try and remove the white ring and stains on my rock waterfall? My pool is only around 10K gallons. I will post a full test result when I get a chance. Thanks for your input.