I've been using my T100 & trusting the pool calculator. These things work together like magic. I punch in my results, I add what it recommends, and the pool does what's expected- even with last years reagents that were stored on top of a refrigerator in the kitchen. The local pool store didn't have much credibility with me before. 2 weeks ago they tried to sell me a bag of dichlor that "didn't have stabilizer in it". That destroyed any credibility they had with me.I'll still buy parts & liquid there, but that's about it.