Fiberglass Pool, CSI drop, how important

[Tcadwall0]

According to my research, and manufacturer warranty information, etc. I know that even though I have a FG pool I still need to manage CSI but with a little less criticality. I am not closing, but the water is too cold to swim.

Does negative CSI impact any equipment or the gelcoat in a negative way? I have been trying to be in the -.3 to -.4 range to reduce SWG scale, and it seems to have worked, but now I am not using SWG for the winter.

That said, my numbers have been pretty stable, but my pH crept to about 8, and I targeted 7.5 with an MA dose. But then my reasonably negative CSI dropped a lot. I haven't done much to bring TA up, but if I plug in a higher TA it doesn't show much impact to CSI either. I could add some CH, but before doing that, I thought I would ask the pro's here. I hadn't checked CH in about a month, and it also has dropped by 25 from 275 to 250. Playing with Pool Math, even bringing CH up to 350 makes little impact to the CSI number.

Before adding the MA one week ago my numbers were:
FC: 8
CC: .5
pH: 8
Temp: 58F
CSI: -.43

Current chemistry:

 

[Texas Splash]

CSI is not applicable to your equipment and should have no bearing on your gelcoat unless you have a waterline tile. It's primarily a tool for plaster management. That said, it is common for the pH to rise in cold water and it helps to counter-balance the cold water's effect on CSI. So ever though CSI doesn't apply to you, I would allow the pH to rise to the 7.8 - 8.0 range. No need to fight the natural effects of cold water, and no need to add calcium or adjust the TA at this point.

 

[Tcadwall0]

Thanks Pat!