CYA level reduction in pool

Jump to latest Follow Reply
S

sjoshi

Bronze Supporter
Jul 3, 2023
44
Venice Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Hi all, it has rained but no more than a couple inches since I tested the CYA level about 2 weeks ago. The measured CYA level seems to have dropped from rounded up 80 to rounded up 60, or even 50 could be justified based on how closely you look. The only chemical addition to pool is a little bit of muriatic acid. It seems odd the measured CYA level has dropped this much (represents a 25% change in volume in the black dot tube). Both measurements were confirmed multiple times, and in fact the level was originally where it is now before I bumped it to about 80. Taylor test kit, fresh bottle of reagent, same bottle used last few weeks during 50 to 80 to 50/60.

Other tests: FC 8.5, CC zero, ph 7.7, TA 50, Calcium 550. I am now going to reduce FC because i dont need it this high if CYA is in the 50 ish range.

I do use two pool robots, Dolphin E70 and a solar powered skimmer. Not sure if these robots could interact with the stabilizer.

Appreciate any thoughts. Thanks!
 
One thing I've learned about the CYA test it to give it a bit of flex. Even with the 10-15% variance, it's not as consistent and predictable as the other tests, and it can be frustrating. :brickwall: Go with your average results from multiple tests at one sitting and call it. Add to that the 5-10 ppm degradation for any given month and the result can change. Sounds like you're proactive and staying on it. :goodjob:
 
  • Like
Reactions: sjoshi
TY much! all 3 times - the original 50 /+ , increased 80, now roughly 50/+ were measured 3 weeks apart, with two types of multiple readings In each test session. Same mix, re-pouring; new mix, new pour. While i am sure some of the difference is driven by things like lighting, I have tried to be consistent - do it outdoors, back toward sunlight, hold at waist level, look with one eye. If the test itself is not that accurate, and difference is 25% of volume in the dot tube, do I need to find a more reliable test? If I am losing some part of this difference in 3 weeks due to natural loss, trying to learn why. All the literature says CYA goes down with dilution and there has not been much dilution mathematically.

Also, our pool seems to be consuming just 0.08 ppm FC per day right now with the now bit-reduced reduced sun intensity (south facing) and our semi regular swims. IC 40 running at 15% for 9 hours a day. CC always zero, pool is always free of organics and say max 5 swims each a week for 2 adults, 20 minutes each. It is hard to determine the non-stabilized chlorine and it’s loss when I am not sure about the stabilizer level itself.

System is pretty dialed in I would say after a few months of learning, testing, fixing. I am fine with wherever the stabilizer is, but I am not sure where it is :)
 
Last edited:
Dont sweat it! The cya test can easily be +-10 depending on the light. Variation of 20 is more than ideal but it happens. There isn’t a better way to do the test. As long as your chlorine is stable, you’re fine. Just keep it well above the minimum level (i would use the higher cya for the minimum to be sure - but it’s only a difference of 1 ppm)
 
  • Like
Reactions: sjoshi
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply