This may be a bit much, but I need info about the relationship between pool company computerized water testing and chemical sales. I suspect one supports the other.
Anyway, had my pool installed in early 2013. Started with the Rainbow 320 tab feeder for chlorine. The pool company provides free Biogard computerized (ALEX) water testing whenever I want it. They also gave me a Poolmaster water test kit (no CYA tests in it). I tested my water a couple times per week and took a sample in about once a month. The manual and computer testing were close in readings most of the time. However, ALEX informed me that the impact rising CYA had wass, of course, on chlorine...but there was more emphasis on the impact on total alkalinity. Seems while my manual reading of TA was similar to ALEX, depending on the CYA number, the EFFECTIVE TA was 1/3 to 1/2 the manual testing reading. So, they always wanted to sell me between 4-18 (!) pounds of Balance Pak 100 (baking soda). Then, since the TA was higher after adding the Balance Pak, of course I had to add muriatic acid to reduce the pH.
The upshot of all this was I got lots of white scale developing on my colored paster pool steps and sides. I went back and forth with the builder and their plaster "experts" and they all agreed that it was the big, bad CYA's fault. The highest CYA number was 140. Allegedly (even with all the testing and chemical adjusting) the CYA was creating a condition where the water was "hungry" and pulling the calcium out of the plaster......hmmmmmmmmmmmmmm.
So, after listening to this for a while, I decided to drain a bit over half the pool, acid washed the steps and sides, and refilled. CYA now at 60. Also, ripped out the tab feeder and used the BBB method over the winter, relying just on test kit testing. No problems. This weekend I installed an SWG and (shudder) took a pre-salt water sample in for ALEX testing. Guess what....TA was way low and they want me to mix in 17.5 lbs of Balance Pak 100 and then reduce the pH by dumping in their "pH reducer" (they would like me to use their dry product in my salt pool rather than muriatic acid). I informed them my TA test indicated 120 ppm and pH was 7.4....so I was not going to do anything other than dump in the salt.
Anyway, after all this, I have seen the chart for calculating the impact of CYA on chlorine. Any guidance on the impact (or not) of CYA on TA? Also, anyone else have any experience with computerized water testing? Seems it's a great way to sell pool chemicals......