Achieving a stable high PH to raise CSI

[Arp]

Hey all,

I have a low CSI problem which I suspect is causing calcium to leech from waterline pavers.

I have an SWG and gas spa heater - based on TFP recomended levels (and manufacturer specs) I'm under the impression I can't push CH above 400 and TA above 100. If these are caps, then I need a high PH (near 7.8) to keep CSI between 0.0 and -0.3... but it stubbornly reverts to 7.3.

But... I'm wondering if I am overthinking the levels here? Is it correct that so long long as CSI is within acceptable range, it doesnt really matter if I push CH higher? That high CH/TA/whatever is only a problem it CSI rises with it? If so... can I increase CH, and TA a little bit, to counter the concerningly low CSI that comes with 7.3 PH?

If not... and tips on how to stop PH drifting to 7.3? Or do I need to keep airating / adding things?

If needed, I'm currently at around:
FC around 5 or so
PH 7.3 (i hate this number now!)
TA 90
CH 400
CYA 85
Salt 3000

Thaaaaaaaaanks in advance... and I hope this makes some sense

 

[mknauss]

Is this pool covered most of the time?

 

[Arp]

mostly yep, although when it is hot in summer we may go a few days, a week or two at most, uncovered.

 

[sande005]

According to PoolMath, your CSI is currently -.38 (if 80F). So outside the range, but not by much. Read more about it here: CSI and LSI - Further Reading
That article notes :
"Technically, CSI is an indicator for scale and not etching although by extension there should be a corollary to etching. Etching doesn't start at a particular CSI level but is related to the probability of occurrence. So a CSI of -0.6 would theoretically have twice the etching potential as a CSI of -0.3 (log scale) but both would still be extremely slow. Based upon some testing by onBalance, even a CSI below -0.6 showed very slow etching.[4]"

So your current level is likely, if one can see any detriment at all, to take a long, to very long, time to have any effect.

Others can suggest ways to help your pool increase its pH.

Easiest for CSI would be to increase the average temp of the pool to move the CSI a bit.
General CH range is 50-650, so going up to 600 would bring your CSI well within range. But if you do get the pH to move up, then you will go the opposite direction with CSI.
The PoolMath app can help you play with the numbers, since CSI is so interactive with several different levels at the same time.

But with a fiberglass pool, and being only a tiny bit on the "bad" CSI side, I'd look to other reasons for your paver issue.

 

[mknauss]

mostly yep, although when it is hot in summer we may go a few days, a week or two at most, uncovered.

Covering a pool traps CO2 in the water. You need to remove the cover more often (during daylight hours) and your pH will rise naturally.

A TA of 90 would not support a pH of 7.3 naturally. Though your high CYA (90) means a good portion of the TA is not carbonate alkalinity.

 

[Arp]

Thanks so much. I've spent sooo long reading - never would've figured this out myself You're all fantastic for putting so much effort into helping people for no reward.