I just took a water sample from our closed pool to calculate how much salt/CYA I would need for opening. We had a lot of precipitation in eastern PA this winter (water is up to coping), so I was expecting a good amount of dilution. However, the CH drop was more significant that I would have thought. It was at 475ppm at closing, and was at 75ppm from the sample I took. Pool math says I would have needed to replace 85% to see a 400ppm decrease.
Do any chemicals like CH "settle" to the deeper water of an uncirculated pool? Are any of the tests not accurate in cold water?