Ok so.....this is where i'm at. A customer called us a week ago to close a pool. I checked the levels in the pool and the PH was below 6, ALK was 0. They had been using HTH trichlor tabs for at least this season. Also i'm pretty sure they never adjusted PH.....or checked it. So over the last week I raised the ALK to 100 PH to 7.6. Now upon returning to the pool over the weekend the water has turned blue and blue flecks are precipitating out of the water. This is to the point it will stain....if I dont let it collect in the filter. ......now I have seen this once before, after being called when the pool turned blue. Now both of these have 2 things in common, they both used HTH and they both had thier PH adjusted drastically over a few days (using soda ash, and sodium bicarb for ALK). Does anyone have any experience with this? I believe it is a chemical reaction between the PH and the clarifier that's included in the HTH.