Link compares kit and has links to purchase each at the very top.
There isn't a single perfect LSI/CSI calculation since no one exactly agrees on the temperature-dependent solubility product constant for calcium carbonate (among other things). I based my spreadsheet calculations on data that was closest to what the Taylor watergram gave using CODATA thermodynamic values plus CRC Handbook data. The Pool Calculator uses a slightly simplified version of what is in my spreadsheet (it does not account for ion pairs, but that's only a 0.02 error). Also note that the Taylor watergram has no way to account for TDS so it is assuming a certain TDS number (you might ask them what they used for that assumption) so will be too high for SWG pools. Now there is another variation for LSI in the APSP-11 standard that is around 0.1 higher than my calculations. All of these are close enough to each other to protect plaster and prevent scaling.Woodberg said:The kit also comes with the watergram that allows me to test CSI. I also use the pool calculator, but they are always a little off. Plus I think the analog watergram is kind of cool.