Low CH with high pH


Active member
Jun 14, 2022
After recently completing an RO treatment on my pool, I'm left with very soft water (CH 130). I am currently topping off with softened water and was planning to switch over to unsoftened water for a while to get the CH higher. I am wondering though if it would be safe for the pebble tech surface to maintain the CH below the recommended minimum of 250, since my pH (as well as TA) tends to always drift upwards (about .1ppm/day) and with a higher pH along with higher CH there would be increased risk of developing a calcium ring. My softened tap water tests at pH 7.7 and TA 150. According to my tests results today, CSI is near perfect. I did add some acid to target a pH of 7.6. I find it requires more frequent additions of acid to keep the pH lower than 7.6. After playing around with some numbers in PoolMath, it seems like a CH of 150 would give me some flexibility to let my pH range between 7.6 to 8.0 and still stay within the +/- safe range for CSI. Am I missing anything?
FC 6
pH 8.0
TA 70
CH 130
CYA 43
CSI .04


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Technically, you can keep the CSI neutral and things should be fine. But as you are going to be able to use softened water from here on out, I am not sure I would chance it. Really up to you. It appears you use liquid chlorine. You could switch to cal hypo, something I thought I would never say here in the SW desert (!), as it would add some calcium slowly.

I would use un-softened water until your CH gets to above 250 ppm or a little higher. Might get there by early winter.
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