Your water is too aggressive and is at risk of etching the plaster. CSI needs to be above -0.6 and -0.3 would be better. Raising pH to 7.8 should get you there. More here, Pool School - Calcium Scaling
I just wanted to add that you're running your CYA lower than TFP specs, but I think you already know that based on your "ideal" parameters cited in your footer, right?
Ok, if you're trying remove some scale then leaving your CSI at -0.8 to -0.9 will help to dissolve it. Sloooowwwlllyyy. FC is holding ok because the days are shorter, cooler and the sun is less intense.
FC 4.5
PH 7.6
TA 70
CYA 80 (Added yesterday)
CH 375
CSI -.57
I'M thinking I should boost TA by 20, then set the Ph at 7.6 or so. Then redo.
I'll be watching CSI as we get more rain. It seems I need to get to ~ 200 CH to get into that CSI zone. I don't want to sacrifice calcium from my plaster.
TFTestkits has very fresh reagents and will get your order in the mail quickly. Lots of options for full refills on TF-100 or K-2006 kits or individual reagents for each kit.
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