Just received my TF100 test kit and I seem to have a problem. CH test is at 1000ppm and all other tests are within normal range. Before using the Tf100, one pool store test showed CH at 1100 this was about a month ago. Drained pool about 2ft and refilled had store check again and CH had dropped to 600 using there tests. When I received my test kit three days ago it showed it was at 1000, again I drained approx 2 feet refilled, ran pumps and kept flushing for about nine hours, ran pumps overnight and the TF100 showed CH at 1000. This morning I took a sample to the store and there it came up at 400ppm. Water is crystal clear and the pool is about two years old,12000 gal,crystal stone finnish and Auto pilot SWG. Fill water checks at 100 ppm with the TF-100. Any help would be appreciated!