CSI about perfect at pH 7.8... risks?

[tominabox1]

I've noticed my CSI is almost exactly zero right now with the pH at 7.8. If I drop it to 7.4, the CSI goes below -0.3 without changing anything else. What is the best way to manage the pH with it "best" at the high limit? Should I adjust something else?

FC 8.5
pH 7.8
TA 70
CH 250
CYA 60
CSI -0.06
Temp 81

 

[pooldv]

CSI anywhere in the range is fine, -0.6 to +0.6 is good, -0.3 to +0.3 is great. No need for a best or perfect number, 0 is not better than -0.2. Same for pH, pH at 7.8 is fine. In fact, it is typically easier to keep pH around 7.8 than it is to keep it lower. The farther away you get from 7 (midpoint) the bigger the jump in pH because it is a logarithmic scale, which means ph at 8.0 is 10 times more basic than pH at 7.0. So, 7.1 to 7.2 is a smaller jump than 7.8 to 7.9 is. When pH gets to 8.0 lower it to 7.6.

I assume you don't have a saltwater chlorine generator since there isn't one in you sig. If you did have SWG my answer would be different.

Also, your CH is a tad low. It's ok for now, but when the temp drops this winter you will be at risk of etching your plaster if CH doesn't rise enough on its own due to evaporation. We etched our plaster the first winter we had our pool due to low CH and not aware of CSI. So, if CSI is still -0.6 or lower in October/november or so then you may need to add some CH to keep your CSI above -0.6. Higher pH will also help to keep CSI up.

More about CSI here, Pool School - Calcium Saturation Index (CSI))

 

[tominabox1]

No SWCG, though we'd love to put one in someday. I still need to do a full test on the fill water but I think the CH is pretty low which is keeping my pool lower. I can see the impact to the CSI in the app with higher CH so maybe just bump it up now to put me at ease. I'm not sure the plaster isn't already damaged to some degree after 25 years of pool store maintenance before I bought the house. I should try to take a picture tonight.

 

[pooldv]

The CH and TA in our fill water in DFW fluctuates depending on rainfall. When it rains and the lakes are full TA and CH are lower. When in drought and the water sits in the lakes the CH and TA rises.

 

[tominabox1]

If I wanted to use cal-hypo to raise my CH, would that be a cost effective way or should I just add some calcium hardness increaser by itself?