How likely is CYA zero from 40 last year?

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2002sheds

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Apr 15, 2013
174
Beautiful Santa Rosa, CA
Hi,
I am just opening our 18,000 gallon gunite pool, and I am using chlorine at a rapid rate as I get the water clean.
I finally did a CYA test today, and the results were surprising -- I detected NO CYA.
I am definitely going to re-test, but thought I should ask... How likely is this after the pool has consistently had CYA levels (for many YEARS) of between 40 and 60?


Thanks,
David
 
When was the last time you checked CYA and/or added any stabilizer? It is possible to lose it and certainly does happen, especially if some environmental conditions are perfect and FC drops to zero. Now might be a good time to post a full set of test results for us with your TF-100 or Taylor K-2006.
 
Hi Marion,
Not at all... So I will re-test, but wonder also if there is a shelf life to the reagent...


MarianParoo said:
Pat has you. I am wondering also: was there any cloudiness to the CYA mixture in the vial?
Click to expand...

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Hi Tex,
The last time I checked it was last fall. It has been checked about 20 times over the years, whether by myself and/or the pool supply store, and it was always in that 40 to 60 range, and always after being winterozed very carelessly (like almost not at all).

Thanks,
David
 
No need to retest. I was just wondering as sometimes if there is cloudiness it can indicate that you have some CYA, but not measurable CYA. Occasionally people think it is zero and adjust for that and there actually is SOME in the water and they end up higher than target. That's one of the reasons I asked.

How old is your reagent? Also, like Pat said, give us a full set of results.
 
David, my battery is low and I'm about to turn-in for the night. :) So I don't want to leave you hanging. I haven't seen your test results yet, but I'm assuming your FC must be very low right now or non-existent. Would that be true? Also wondering if your CC level is elevated. So there are two options to consider here: Either you simply have organics/algae that is consuming FC very quickly and you need to stick with a SLAM, .... OR with no CYA and FC depleting exceptionally fast, your CYA may have converted to something else like ammonia. With no tests I can't tell for sure. But I would still consider conducting this test first:
- Add only enough bleach to get your FC to 10. Test it again in 10 minutes. If your FC held between 5-10, then increase it to 12, then add stabilizer for a target of 30, and perform a SLAM (link below) like normal. If your FC fell below 5 after just 10 minutes, increase it back immediately and test again in 10 minutes. Continue this cycle until the FC holds after 10 minutes.

As you can see, either way it's very important to stay on-top of the FC testing in this early stage - every 10 minutes at first. It's required to allow the FC to hold better and overtake what's in the water. Now if the 10-min drill doesn't work after a couple hours, you do have the option of doing a partial drain to remove some of the bad water if you prefer to help kick-start the cleaning process a little better. Some situations find that a partial water exchange might be more cost-efficient at first. But you would still need to SLAM once filled back up. If water exchange and time are a factor, I would go right to the 10-min drill first. But make sure to have a good amount of bleach ready when you do.

David, you'll need to watch the FC very closely for the first couple hours or so until it breaks this "fever". Don't add stabilizer until you see the FC is holding on its own past 10 minutes. Let us know if you have any problems or questions.
 
Hi Tex,
Thanks very much for the great step-by-step advice! The pool was dark green upon start-up, but it is 100% my fault. The pool is at my Mother-in-Law's house, and I do not go over enough except in the summer, when our kid swims every day. At least a good deal of the chlorine use is legit. The pool is now blue but somewhat cloudy (visibility to about 2 feet).
I will head over there and test in the morning and report back.


Thanks Again!
David
 
Following this web site it seems more and more people are reporting full CYA loss over the winter. Bacteria derogating and converting into ammonia seems to be the cause. Did you have a significant amount of dead organic stuff on the bottom? Earthworms, decaying leaves, mouse, toads, etc. Also what kind of cover do you have? Solid or mesh?
 

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censored said:
Has the pool been covered? My CYA level has lowered a bit due to the heavy rain we have had this year and then some evaporation/refill from the last couple weeks.
Click to expand...


The pool was not covered, so great catch!

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Hi Mike,
Thanks for the reply! No mouse or toad -- at least not yet (I'm still cleaning and cannot see the bottom), but a fair amount of leaves that I am nearing the end of.


Thanks,
David

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Hi Fellow Packer Backer,
This us great advice. I re-read Tex's recommendation, and due to the severe drought here in California, I do not have the option of a partial drain of the pool.
I will report back with test results, and go with the SLAM process.


Thanks,
David
 
Dichlor is fine to use when you need to increase both FC and CYA. You can use the Poolmath calculator's "Effects of Adding Chemicals" row to tell you what you expect based on the amount you plan on using. For a SLAM, you can expect that bleach will still be your primary sanitizer. If the Dichlor doesn't increase CYA as quickly as you would like, stabilizer may still be required.

If you haven't yet done that 10-min drill, I would stick to the bleach at first. It's fast-acting and won't raise CYA which you don't want to do until you know for sure you can hold some FC to rule-out ammonia. Do that first, then sure ... bombs-away with dichlor using the calculator. :)
 
Hi All,
The test results are in...

Gunite pool, 18,000 gallons

FC = 1
CC = 2
PH = 7.0
TA = 120
CH = 180
CYA < 20

I used a fresh CYA reagent. I had dumped 4 gallons of 12.5% liquid chlorine in yesterday...
The pool is slowly clearing (our method is to note how many steps on the shallow end we can see -- currently, it is a little more than one), but clearly I need some stabilizer.
My plan is to add enough chlorine to get the pool to 24 ppm and also try to add some stabilizer.
Question: how quickly does Dichlor add CYA?

Thanks,
David
 
Hi All,
Sorry -- we were gone for a week. Now I am back at it...
Before I left I added enough stabilizer to get the CYA level (which seemed to be non-existent, and that was confirmed with two tests and new reagent) up to 45. I also added enough chlorine to get FC to about 22, to further eradicate any remaining algae.
Upon my return, I just tested CYA, FC and CC. My results were:

FC 2
CC about 1.5
CYA 45
PH 6.8

The pump is not straining (the gauge on the filter is at 2 pounds over "clean").
I vacuumed before leaving, and brought up fairly little at this point.
Our unofficial clarity guide is to check how many steps we can see on the shallow end. Out of three steps, two are now clearly visible and the bottom step is fuzzy, but visible.
My approach now is to shock the daylights out of the pool until it further clears (and holds chlorine overnight). Anything else I may be missing? I was going to address PH once FC holds overnight and then comes back down into the normal range...or should I address it sooner?

Thanks,
David
 

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