Hello Grey. I'm in Katy--old Katy just north of Katy City Park and off Avenue D. We're on the edge of the ancient Katy Prairie, and the south wind blows here pretty much all the time, except some of the winter when it blows from the north. I've notice this year more than last at setting of 40% on my Pentair IC-40 SWCG has a harder time maintaining 6ppm FC. My approach when both FC and CYA are low is to put some tabs in a floater and the floater in the spa, which spills over into the pool. We have run the heater more than last year, and I'm sure the wind and sun take their toll. I've also this year had a lot more seed pods from nearby Purple Vitex flowering trees. Another thing you've probably heard is the Sahara dust which keeps the sky from being blue, and which also quietly settles into the pool, but other than creating a bit of mud for the the robot, I don't know about its impact on a pool or pool chemistry.
I add muriatic acid a couple times a week, but just a couple cups worth. Last drop in FC I used the floater as well as bumping the IC-40 up to 50%, and that brought FC from 5 to 9 in five days. I also put some stabilizer in a sock to get the CYA up faster than just the tabs alone. The pump runs at 1600rpm 8am to 8pm with the IC40 also running that schedule. With our mini drought, I've added water a couple times. Sometimes I overshoot with adjustments, preferring FC to be high rather than low.
Incidentally, I think I read your reference to a possible Hayward T15 SWCG being considered? The general recommendation I've read here is for a SWCG with double the capacity of your pool. I'm not familiar with the T15, but if the 15 refers to gallons, then that may be a bit small. My 15k gallon pool is running a Pentair IC40 (the 40 refers to gallons of capacity at 24 hrs a day). In winter it runs around 8-10% for ten hours. Now it's 12 hrs at 40%. You can see from my Poolmath logs the swings I've had.
Just tested again. I think yesterday's CYA must have been a mistake. Tested twice today, and it's back at 60 and FC at 7. Yesterday was at 2pm (CDT); today at 4:45, and the water temp is up to 91 from yesterday's 89. After yesterday's test, I turned the IC40 down from 50% to 40%. Wind comparable 22mph yesterday, 23mph today. It's windy here on the prairie. This may be too much info, but I'm trying to give you what I'm seeing in a similar environment.
