It turns out that the reagents for the LaMotte unit for CH testing were slightly out of date. So, I ordered new ones. After getting the new ones, CH increased to 417. Obviously, not low like the previous measurements using the outdated reagents. However, the Taylor test kit shows CH at 570. I took my pool water to a local pool supply store and they showed the CH at 370. Three test, three different results! I know that store results aren't good to follow. But which of these measurements do I believe? It's like trying to shoot at a moving target. How can I be sure which one is reliable? Also, the Taylor unit consistently shows PH to be 0.2 higher than the LaMotte unit.