Finding the CYA sweet spot

[NocturnalDoc]

Looking for advice on CYA level...

CYA 30
pH 7.5
TA 130
CH 260
CC < 0.5
OCLT 1 ppm

I seem to be using a lot of bleach, FC to about 6 after dark, and by 3 or 4 pm next day FC is about 1 (Min should be 2 with my current CYA). Adding 5 ppm is nearly a gallon (112 oz) of 12.5%, which costs me about $4.50/day (more than I expected to be spending on bleach). Actually, many days I'm adding 1-2 ppm of bleach in the afternoon, to avoid dropping below the min, so my cost is more than calculated above.

I know I'm fighting a lot of sun... Redding, CA (far Northern CA), full sun all day, and it's been 95-105F this past week or two. I'm concerned if I bump up to CYA 40 or 50, I'll need higher FC levels that just drop faster in full sun, i.e. I think I read somewhere here FC drops essentially with half-life kinetics. Will the extra CYA lengthen the half-life of FC? If so, I it would make sense to increase my CYA.

Thanks!

 

[Smykowski]

Yes, I'd bump it to 50. There seems to be a tipping point on CYA where all of a sudden the FC drop slows down drastically once your CYA threshold is crossed.

 

[Whatrymes]

Yes, I'd bump it to 50. There seems to be a tipping point on CYA where all of a sudden the FC drop slows down drastically once your CYA threshold is crossed.

That's been my experience exactly. I was hoping to keep my CYA at 30 ppm but was losing 'bout 4 ppm of chlorine a day. After raising the level to 40, and after a few days, suddenly my chlorine loss slowed down significantly. We are now losing 1 - 2 ppm a day.

 

[NocturnalDoc]

Thanks for the quick replies! I just added CYA to the sock, aiming for 40 ppm. I'll check it in about a week, and see how it goes, then bump up to 50 if I'm still losing too much FC.


22,500 gal, IG plaster
Pentair FNS Plus 36, DE filter
3/4 HP WhisperFlo pump
BBB believer, trying to be disciplined enough to make it work!

 

[Bama Rambler]

I run mine at about 50ppm or a little higher.

The first thing to do is run a OCLT to make absolutely sure it's not organics eating the chlorine and then start raising the CYA until you're losing about 2ppm per day (24hrs).