Need help with PH and TA (long post, sorry!)

[waterbear]

I would try and adjust the pH first and see how it holds. If it is bouncing then you might want to raise the TA a bit. Vinyl pools seem to do better with a TA of 100-120 as long as your calcium isn't too high. If your water is very hard you might get some cloudiness or scaling if the TA goes too high and the pH rises. I personally would check it when the FC is on the lower side of the range....maybe 5-6 ppm. Some of the phenol red just doesn't do well with higher levels. Depends on which test kit you have. Pentair is one of the ones more prone to the interferance from what I have seen from my own experience with their phenol red.