CYA gone from 57 to ZERO in 2 days?

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Poppaspool

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May 12, 2018
15
Wingate, NC
Our pool liner, and the ladder steps, and skimmer opening, were an ugly dark pinkish red. Did the ascorbic acid test, and it was instantly white again. So I got some powder and got rid of the stains, according to the article here.

The sequestrate took a while to get here (we don't have pool stores close by) and after a few days, we had more pink stains. Not bad, but still, after seeing a white liner, I didn't want to see ANY pink. SO I added a little more vit c, it cleared it up within 30 minutes. Turned the sand filter back on to filter. Added the Jack's purple stuff.

My CYA has been 60-70 for years. I use tri-chlor and regular bleach to sanitize. I have NEVER ever had the CYA go down more than 1 or 2, after vacuuming to waste and re-filling pool.

Wed I tested everything, because the pool is milky white after the vit c treatment. CYA was 57. I tested after I filled it up, the grandkids were in it a lot, and it has been very hot. Today, pool is still milky white, and CYA is zero.

I tested it 3 times. The test kit is brand new, the TF-100.

I have been taking care of this pool for 18 years, NEVER have I had this happen!

Does anyone have any ideas? Can ascorbic acid deplete CYA?

pool is:
18,000 gallons
vinyl liner
pH 7.2
CH 400
FC today 2
sand filter, sand is 3 years old

I backwashed the filter yesterday, pressure is normal.
 
Welcome to the forum!

Have not heard that before. The AA treatment takes chlorine to recover from but have never heard of a CYA issue. CYA disappears due to water exchange, ammonia, and oxidation. First two are quick and the last one is very slow.

Test CC next time you do a chlorine test. Ammonia would show an elevated CC. But ammonia is really unlikely.
 
benm2010 said:
Ok, just making sure that both the 57 and 0 both came from you and your testing (FYI the scale for CYA is logarithmic and is hard to distinguish that small, I believe most people here will tell you to call it 60). Was the chlorine ever 0 between the two tests?
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Yes, the chlorine was 0. And sure, saying it was 60 is fine. It is not an exact reading, on any CYA tests I have used.
 
Well, if you want, you can test for ammonia.

Add enough LC to raise your FC to 10 ppm based on PoolMath. Circulate pool for 30 minutes. Test FC. If at 5ppm or lower, add LC to get back to 10 ppm FC, circulate pool for 30 minutes, test FC, repeat until that test shows a FC of greater than 5 ppm.
 
mknauss said:
Well, if you want, you can test for ammonia.

Add enough LC to raise your FC to 10 ppm based on PoolMath. Circulate pool for 30 minutes. Test FC. If at 5ppm or lower, add LC to get back to 10 ppm FC, circulate pool for 30 minutes, test FC, repeat until that test shows a FC of greater than 5 ppm.
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MK beat me to it. If your chlorine is zero, there is a bacteria that consumes CYA and produces ammonia. Perform the test above to determine if you have ammonia. Another possibility, you said the water was milky white when you first tested the CYA? In rare instances the CYA test can be affected by cloudy water causing a false positive when no CYA is present.
 

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benm2010 said:
MK beat me to it. If your chlorine is zero, there is a bacteria that consumes CYA and produces ammonia. Perform the test above to determine if you have ammonia. Another possibility, you said the water was milky white when you first tested the CYA? In rare instances the CYA test can be affected by cloudy water causing a false positive when no CYA is present.
Click to expand...

Yes, pool was cloudy Wed when 1st tested, and still cloudy today.

And, what test shows ammonia?
 
There are aquarium test kits for the presence of ammonia, but you really don't need one. If the FC is gobbled up that quickly you have ammonia and the way you get rid of it is with very frequent additions of liquid chlorine. Do not use any stabilize chlorine powder or pucks until all the ammonia is gone. Adding stabilizer too soon prolongs the problem.
 
Actually, you might want to wait on the SLAM Process a bit and first just see if FC will hold to your normal level.

You just did an AA treatment. The AA leftovers fight the FC to depletion. While the cya is mystifying, slamming if it will hold without means you will oxidize all that sequestrant you just put in and risk the return of staining.

So while you want to do small, frequent additions of FC to get it to hold, once you’re holding, is possible, do an Overnight Chlorine Loss Test first to see if you actually need to slam.
 
Thank you Swampwoman!

I found some 10% bleach at Lowe's. I do not know what the date on it is, but we have now bought all the bleach that is not scented at both grocery stores near us!

Today, FC still barely hovers at 1 after 30 minutes of adding bleach, BUT! we can now see the drain in the deep end! So I know it is improving.

I will do the overnight chlorine loss test before I slam.
 
It took 23 gallons of bleach to get the FC to read above 2 30 minutes after putting it in the pool.

We found some 10% chlorine at Wal Mart, after we bought ALL they had at Lowe's.

I do not shop at Wal Mart, for personal reasons, but had to make an exception because I want to use my pool again sometime this summer.

Now the pool is a beautiful green :sad:

When do I add CYA?
 

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