CYA Disappearing

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H

huntero

Member
Dec 15, 2022
6
Florida
Hello TFP,

I'm hoping you all can help me with a pool water mystery. I'm struggling to keep Chlorine in my new-ish gunnite pool (built 9mos ago). I have the salt cell running at 100%, 12 hours a day and I'm having to supplement with liquid chlorine. I'm slightly suspicious of the salt cell, since when the pool was first built I never had to turn it up past 35%, regardless of CYA level.

BUT, I suspect the primary cause is due to lack of CYA, I can't seem to keep levels up. I'll bring CYA up to around 40-50ppm, and usually within 2-4 weeks it's back down to 0-20ppm levels. Combined with the Florida sun, I'm guessing that's causing tons of Chlorine loss during the day.

I've used both liquid CYA and granular CYA to raise levels.

While the water has always stayed clear, I have had a couple of times when Combined Chlorine levels have raised above 1PPM, which made me suspect that the Chlorine dipped too low and now I'm fighting something organic (algae?). In both those cases I've SLAM'ed the pool (followed the protocol) to remove CC.

Since the most recent SLAM, CC levels have stayed at zero, but CYA levels have continued to drop. Just today I measured at 0 CYA (or close to it), and am having to re-add.

I did try a fishtank ammonia test a few months ago and didn't see raised levels.

Any ideas what's going on and how to get out of this cycle? Thanks!

Last test results (TF-100 Kit)
--
FC: 2.5
PH: 8.0 (I aim for 7.5, added some acid)
TA: 80
CH: 375
CYA: 0-10 (slightly cloudy, dot never disappeared)
SALT: 2900
TEMP: 83F

Salt Cell: Hayward T-Cell-15 (should be way oversized)
Pool Size: ~13,000 gallons
 
Hey huntero and Welcome !!!

How's your water bill ? I bet if you shut off the auto fill, you're going to see a substantial leak.

Anytime you see surprising FC loss, visible algae, etc, Overnight Chlorine Loss Test.

you'll need 70+ CYA in sunny Florida. When FC won't hold at 70, add 10 more and road test it.
 
Hi Newdude, thanks!

No autofill, but I add water probably every week or two. I lose maybe a couple inches a week at most? I passed the OCLT after my two SLAM's, but I could give one a go now just to see if an issue has come back.

I'll try bringing the CYA up to 70-80 on my next replenish cycle, I just can't figure out where this stuff is going!
 
huntero said:
I just can't figure out where this stuff is going!
Click to expand...
It's going to overflow and/or leakage and replenishment.

Where are you in FL ? I just read today that some parts have had 20 to 30 inches of rain recently. 30 inches is half a free water exchange for most ingrounds.


huntero said:
I'll try bringing the CYA up to 70-80 on my next
Click to expand...
Never raise CYA substantially without an OCLT. Slam jumps from 12 FC at 30 CYA to 28 FC at 70 CYA. It is a costly difference for the SLAMer.


huntero said:
but I could give one a go now just to see if an issue has come back.
Click to expand...
With your FC being repeatedly wiped out, pass an OCLT then get CYA back in there.
 
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Newdude said:
It's going to overflow and/or leakage and replenishment.

Where are you in FL ? I just read today that some parts have had 20 to 30 inches of rain recently. 30 inches is half a free water exchange for most ingrounds.
Click to expand...
Orlando area - we've been unusually dry up until this week. About 7 inches recorded Jan-April in 2024, but we've finally gotten some rain this week, I'd guess an inch or two.

Good advice! I'll hold off on the big CYA increase until I can make sure to pass an OCLT.
 
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How do your salt and CH compare ? Have they been rock solid , drop as much, drop half as much, etc ?
 
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Salt dropped to 2500 in December '23 and I brought it back up to 2900. It's been pretty steady at 2900 in 2024. CH was around 250 when the pool was first filled after construction in August '23 and slowly rose to a steady 375 this year.

Here were my last few CYA measurements:
4-22-24: 40
4-24-24: 50 (I had recently re-added a few days prior, so I'm guessing still dissolving and increasing)
5-5-24: 30
5-15-24: 0 (slightly cloudy, but dot never disappeared)
 
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Meet my buddy @Katodude. He's a fellow Floridian seeing a similar seemingly unexplainable CYA loss. You two can bottle up your pool water and make millions selling it to the Leslie's tab crowd.
 
proavia said:
Do the Overnight Chlorine Loss Test and report back.

What brand CYA are yo using?
Post a pic of the container/bag.
Click to expand...
Natural Chemistry Liquid Stabilizer - https://www.amazon.com/dp/B06XXDLMYY
and
Clorox Pool and Spa Swimming Pool Stabilizer - https://www.amazon.com/gp/product/B084GPVPMM
Newdude said:
Meet my buddy @Katodude. He's a fellow Floridian seeing a similar seemingly unexplainable CYA loss. You two can bottle up your pool water and make millions selling it to the Leslie's tab crowd.
Click to expand...
:LOL: Misery loves company!
 

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Start measuring your salt and CH more regularly with your test kit. Without rain, any of those dropping are indicators of a pool leak. Get a baseline now and start (the increase CH on a new pool is probably very normal). It’s hot but not crazy humid yet so you should be losing between 1” to 2” a week due to evaporation. Anything over 2” is suspect.

Also Orlando has been pretty hot lately, what is your pool temp. Apparently CYA degrades at a higher level with pool water at 85 and above. Right now my pool temp low is about 85.

I think I may have also read somewhere that higher FC levels also help CYA degradation.

I also recently bought 50lbs of Doheny CYA which according to some here is supposed to be better, but we will find out.

With RXClear I was seeing your level of losses last year as well.

I will run a full set of tests in a little bit and see what I come up with.
 
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Thanks, everyone, for the suggestions. An update:

I completed a SLAM, passed the OCLT, and then brought it up to mustard slam levels just to try something different. Ended the SLAM, started raising my CYA back up to get some sun protection(currently at 40) and despite the SWG being at 100% for 12 hours a day, chlorine levels began dropping. I'm back to supplementing with liquid chlorine to keep above minimum levels. I'd blame the lower CYA levels which I'm working on getting up, but a week or so after finishing the SLAM, I'm now showing CC levels of 1ppm and have that distinctive chlorine smell coming off the pool, so it doesn't seem like it's just sunlight. The free chlorine never dropped below 4ppm.

Now using the Robelle CYA.

I seem stuck in a cycle. The best I can guess at this point is that there is something environmental in my yard that quickly finds it's way into the pool, survives 'normal' chlorine levels, eats my CYA, then I SLAM, kill it, reduce chlorine to normal levels, which lets it come back. Rinse and repeat.

I've never seen any discoloration in the pool, so it doesn't seem like algae. Or my 9-month old SWG is shot, though that doesn't explain the CYA loss. And it seems to be doing at least something, there's plenty of bubbles out of a return when it's active.
 
Post a full set of test results. Please.

Are you using PoolMath? Homepage, select the gear in the upper right corner, scroll to the bottom and enable sharing with TFP so we can see your logs.

CYA will degrade faster in warmer pools. What is your pool water temperature?
 
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