Trying to get my CSI right

CarolineM

Silver Supporter
Jun 20, 2018
218
Annapolis, MD
FC 7.5
CC 0.5
PH 7.6
TA 70
CH 100 (need to bring up)
CYA 60 ( have sock hanging to bring to 70)
Salt 3600
Temp 78
CSI -0.92

Water is sparkling clear.

Fiddling with pool math adjusting numbers for target range for a Fiberglass SWG pool, I still cannot get my CSI correct .

How important is CH in a Fiberglass pool?

Anything that stands out that I can adjust to get my CSI correct?

Thank you.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
22,053
San Dimas, CA (LA County)
You have no plaster to etch, so it doesn't matter that CSI is negative. If it were positive, you'd need to worry about scale. It''ll head toward positive as it warms up. As the pH naturally rises it will, too. And if you do go ahead and raise CH, that will also push it in the positive direction.

If you're going to add Calcium, do it now, while its too cold to swim in, because sometimes it clouds the water for a day or two and nobody likes that.
 

CarolineM

Silver Supporter
Jun 20, 2018
218
Annapolis, MD
You have no plaster to etch, so it doesn't matter that CSI is negative. If it were positive, you'd need to worry about scale. It''ll head toward positive as it warms up. As the pH naturally rises it will, too. And if you do go ahead and raise CH, that will also push it in the positive direction.

If you're going to add Calcium, do it now, while its too cold to swim in, because sometimes it clouds the water for a day or two and nobody likes that.
Thank you Richard. I will up the CH now and watch my CSI as it heads towards positive.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
6,802
Northern NJ
Raise your CH to 250 and let your pH drift up more towards 7.8

You don't care about CSI that much with a fiberglass pool. Some fiberglass pools need some CH or they get chalky. For that reason I would raise your CH to 250. Then you want to keep your CSI sightly negative so your SWG does not have scale buildup. Use the range of your PH to keep your CSI negative as your water warms.
 

CarolineM

Silver Supporter
Jun 20, 2018
218
Annapolis, MD
Raise your CH to 250 and let your pH drift up more towards 7.8

You don't care about CSI that much with a fiberglass pool. Some fiberglass pools need some CH or they get chalky. For that reason I would raise your CH to 250. Then you want to keep your CSI sightly negative so your SWG does not have scale buildup. Use the range of your PH to keep your CSI negative as your water warms.
Thank you AJW, will work on raising my CH and letting my PH drift up.
 

an1vrsy

Bronze Supporter
Jul 10, 2018
113
Rancho Santa Margarita, CA
Another thing to keep in mind is your fill water. When you replace water due to evaporation you’ll want to know what the water chemistry levels are with that. CH, pH and TA for sure.