Low CSI

Hollybrook · Jul 3, 2019

I am converting our pool to SWCG and adjusting the chemicals prior to installing the system. Even though I have the levels where I think they should be, my CSI is lower than I would like.

Parameter	Test Result	Target
FC	6.0	4-11
pH	7.4	7.2-7.8
TA	80	60-80
CH	325	350-450
CYA	80	70-80
Salt	3,400	3,000-4,500
BOR	50	30-50
CSI	-0.46	-0.6 to +0.6

The water temperature is currently 84, recently coming up from 80 a few days ago.

Since all the individual parameters are within the expected range other than CH, which I have been increasing, I was surprised to see the CSI below -0.3 which is my lowest comfortable level.

Any comments on why this is happening and what I can do to raise the CSI without taking the other parameters out of range?

mknauss · Jul 3, 2019

Welcome to the forum!
Let your pH rise naturally. If it gets to 8, do not lower it below 7.6.

Your water chemistry values are just fine, I would not concern yourself with CSI.
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

Flying Tivo · Jul 3, 2019

You might try aerating if you want a faster rise in ph, but then you could end up in yo-yo effect.

Hollybrook · Jul 3, 2019

Thanks, I have been lurking here for about a decade and am quite grateful for all I have learned. And yes, I have already read the info that Marty linked to.

My pool has been fantastic compared to all the ones I have visited at friends' homes, and that is all due to the great advice I have received from this site! I've gotten tired of chlorinating with bleach backed up with a tri-chlor tablet feeder, so decided to up my game a bit. Its just that I have not followed much about SWCG until now...

I should have the salt cell installed in a few days, so that will drive the PH up once it is running. All my equipment is quite old and I am using the upgrade to SWCG as a reason to rip it all out, install a new pad and replumb/rewire. Should be a fun project!

mknauss · Jul 3, 2019

The SWCG does not really effect pH that much. That is normally stated because people are used to trichlor which is acidic and then switch to SWCG and they see pH rise, because they are no longer using acidic trichlor.

Richard320 · Jul 3, 2019

Just go swimming. The aeration will raise the pH a little.

In the future, when you have to adjust pH, target something higher than 7.4

Hollybrook · Jul 3, 2019

Thanks for the advice!

I decided to add a little more Borax as I did not put the full calculated amount in earlier this week. My test strips only have 10ppm resolution so I suspect I was still a bit under 50ppm even though the strip seemed to indicate I was there.

That should fix my CSI problem by raising the PH, though I will be a bit high on TA for a while. The next time I add some acid, that should resolve itself and I won't worry so much about being corrosive on my 20+ year old pool that is suffering from apparent mistreatment by the previous owners who relied on the local pool store and a bunch of chemicals that I never would have used.