strange test results and CYA level

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ddavis1975

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Apr 10, 2011
17
>I opened my 14000 gal Intex aboveground "green" pool to a nasty FC = 0, pH = 8.0 and CYA = 50. I use Taylor-2006 kit. I shocked it to a 26 and it started clearing up and had a hazy blue. On 3/17 the FC was a 17 and cya 40. I have kept pump working a lot and test/adjusted chemicals till today's test results, which were:
FC = 6.0 (a day after shocking to a 12 with bleach according to the pool calculator)
CC = 0.5
pH = 7.2
ALk = 80
CAL = 130
CYA = zero????
I was shocked at the last one and retested it. How can the CYA drop to a zero? I can understand it being 40 vs 50 due to the algae and Crud in their the first test. I have read on some sites about other owners saying CYA levels can drop to zero in the spring due to chemical reactions and using real high levels of bleach, etc. One site even said algae eat acids. I don't understand all that. Can someone offer some concrete simple explanation on what is going on with my CYA level?

FYI. My pool is cloudy blue. I use cartridge filters. Recently I added CaCl2 to inc Ca hardness and some baking soda to get pH up from 7.0, but it got cloudy. Now I read on a site to avoid adding those at the same time. oops. Crud. I know Calcium hardness doesn't matter for vinyl, but the pool never shows as balanced in the calculator if I don't get that up. I had some chemicals from last year so I used them, but it seems to be a mistake. Another goof was that I read that clarifier and Algacide can cause cloudy water too.?? I used those not long ago. oops. today I added 26 oz of baking soda and 16 oz of borax to raise the alkalinity and pH a little - hopefully pH to 7.4 and Alk to 90. I also added an old bag of dichlor and 10 oz of solid stabilizer. If what I have read is correct, the dichlor will increase CYA by 9 and the 10 oz stabilizer will inc. it by 5. That will only be 15, but I was hesitant to do too much. I don't want to get the CYA too high.
Here are some basic questions if you will please assist.
1. What CYA level would you suggest for a vinyl aboveground pool in Ala? I have read 40 -50 to avoid having to add so much bleach. I was thinking 50.

2. If my stabilizer was zero as it showed, why was my FC at 6.0 24 hrs after shocking to a 12? Wouldn't it be near zero on a warm 80 degree day here in Alabama? What is your take on my chemicals, CYA, and cloudy issue?

3. Should I use the old dichlor shock to get the CYA back up quickly to the needed level? Or would you use the solid stabilizer in the skimmer?

4. Would you use trichlor pucks to raise the CYA for a while? (I still have the pucks and dichlor from before I discovered the BBB method here at the end of last year)
5. How many days does it take to get the CYA to dissolve if it is in the tablet or solid bottle form and get an accurate test result? I have heard to wait up to a week after adding to see where the CYA ends up.
6. How much does one trichlor tablet raise FC and CYA per 10000 gal etc. for future reference? Such as vacations...
7. What levels would you recommend I shoot for and which chemicals to add to get my pool clear? Hopefully getting the CYA right and using the right amount of bleach each day and running the filter all the time will get me cleared up?
BamaFan
 
1) CYA around 50 is a great idea.
2) That doesn't completely make sense. We have seen CYA go away over the winter, and occasionally fall while you have algae and no chlorine, but not that quickly.
3) If you already have the dichlor then this is a good time to use some of it. The one disadvantage of dichlor is that it will lower the PH, which is already at the low end of the range, so you will need to add something (perhaps borax) to bring the PH back up.
4) Trichlor adds CYA too slowly to be of much use in this situation.
5) If you add granular cyanuric acid you should wait a week before testing the CYA level. If you use dichlor or liquid then you can retest after an hour. In either case assume that it was all added right away.
6) The Pool Calculator is a great way to figure this kind of thing out.
7) For right now, I recommend you double check your CYA reading, aim for a CYA of 30, keep PH generally in range (7.2 to 7.8), and shock to an FC of 12 until the pool clears up.
 
Welcome to TFP fellow Alabamian. :wave: Where are you close to?

1. 50ppm CYA is where I run ours and it's in full sun all day.
2. It sounds like a testing error to me. Either the first time or the last. How old is your CYA reagent?
3. See Jason's answer above.
4. Ditto #3
5. Wait a week to test but assume it's there after a day.
6. As Jason said. The Pool Calc is the best way to figure that. For every 1 ppm FC it also adds .6ppm CYA.
7. I'd assume you have a CYA of 40ppm and maintain the shock level for that until you're done shocking or retest your CYA to prove otherwise.

You stated that you have a CC of .5ppm and the water is cloudy. Keep shocking until you pass the OCLT (Overnight Chlorine Loss Test).
 
I recently had a similar experience. CYA should be about 40. Shocked. CYA shows 30. No water added. I enquired whether high FC affects CYA readings as a followup question in a thread and got no definitive answer.

By personal experimentation, I think it does. FC was 7.5 yesterday morning. CYA is a solid 40, tested multiple times. I even ordered the 50% CYA standard solution to check myself, and I was dead on. So I know I'm doing the test right. I haven't added any CYA, so how did it go up? And why did it go down? The only test that has changed more than one drop either way in the last month was FC.

If your bleach seems to be lasting longer than zero CYA would indicate, I'd let it be and finish the shock, then recheck CYA when FC comes down to maintenance levels. You are, of course, free to ignore my amateur advice.
 
Thanks to all for the info. I have been swamped and unable to post. I changed filters and added a pack of dichlor and kept the pump running. I retested and the CYA was 42. The pool is clearing up. Almost perfect. pH is 7.5, and FC has been 3 each afternoon. The target FC level is 5. So I have had to add only 60 oz of bleach each day and raise it up two and it has been perfect. Thanks to all. It still seems that my CYA was gone or more likely not registering under high FC shock levels. the CYA solution was new and unopened.

Hope things stay clear!
 
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