CYA dropped to below 30

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bjbarlowe

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May 9, 2016
54
Lynchburg, VA
This is my first summer with a pool and the TFP method has been wonderful - giving me a beautifully clear pool all summer. At the beginning of the summer, I had a high CYA level and had to replace water to bring it down to 40. I checked my CYA level for the first time in a little over a month today and it is below 30. I completely filled the tube and could still see the black dot. I am out of R-0013 reagent and just reordered a 16oz bottle, so I'll have to wait about a week or so before I can check it again.

First, I'm not real sure how this could have happened since the only way to lower CYA is to replace water. I do get a lot of rain in my area - could that explain it? It's also possible I simply messed up the test, but again I can't confirm it at the moment.

Second, should I even bother raising CYA? I've been maintaining my FC level at 5 ppm, but I only lose 1-2 ppm a day. I very rarely lose more than 2 ppm in a day. If that rate of decline stays the same, do you think it's even worth bothering raising CYA?

I do have some 1-inch trichlor tabs left over from the previous owner I can put in the skimmer basket, so it will be easy enough to raise the CYA.

Thanks for your help!

EDIT:

I thought I should add my full test results:

FC - 3.5 (just raised to 5)
CC - 0
PH - 7.8
TA - 70
CH - 120
CYA - <30

I may test CH again in the morning as well. Borjis's comment below helped me realize that if CYA has fallen I should expect to see CH fall too. This test would indicate it hadn't changed, but I had difficulty with that test today as the sample turned from a very faint red to a very faint blue. It was so faint I may have misinterpreted when it turned from red to clear to blue.
 
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I've just had the same thing happen. CYA is 20 and was 50, 2 months ago.

I have done no drains or backwashes, it has not rained....will start my own thread after
I test CH, if it is the same as it was then I have a magic pool.
 
Same here, mine was at 50 two months ago and I haven't checked it, decided to check it today and it's below 20. Weird. I've been having to add more chlorine lately so that's why I suppose. It's so hot here, the pool water has been at 94 the past couple of days. So refreshing!
 
I was going to start another thread on CYA going down as mine has as well to even a larger extent but I've been trying to research all the threads out there first to not be redundant. It does seem to go down despite no obvious reason like draining or excessive rain.
 
After reading some other threads on this (which I should have done before posting), it looks like CYA can degrade faster than normal if 1) Your FC level drops to 0, or 2) your FC level gets to high levels relative to CYA (at shock level) for a considerable period. Another factor that leads to faster CYA degredation is higher water temperatures. My FC has not gone to zero, but I have taken two weekend trips where I brought the FC level to or above shock level so I wouldn't drop below the minimum while I was gone. That and heavy rain plus a couple backwashes may have caused this.

I'll retest when I get more reagent next week and just switch to my trichlor tabs for a little while and/or add liquid stabilizer if I need to.
 
bjbarlowe said:
After reading some other threads on this (which I should have done before posting), it looks like CYA can degrade faster than normal if 1) Your FC level drops to 0, or 2) your FC level gets to high levels relative to CYA (at shock level) for a considerable period. Another factor that leads to faster CYA degredation is higher water temperatures. My FC has not gone to zero, but I have taken two weekend trips where I brought the FC level to or above shock level so I wouldn't drop below the minimum while I was gone. That and heavy rain plus a couple backwashes may have caused this.

I'll retest when I get more reagent next week and just switch to my trichlor tabs for a little while and/or add liquid stabilizer if I need to.
Click to expand...


Maybe thats why my CYA levels have dropped as well. Hmmm interesting..
 

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JesseSchmidt said:
I was wondering if you lose CYA to evaporation. Mine was 50 and the last time I checked it a week ago, it was 40. I lose around 2-3" of water a week to evaporation right now. So does anyone know if the CYA goes with the water when evaporation happens?
Click to expand...

As far as I know, you can't lose CYA due to evaporation. From what I've read here and elsewhere, the only way CYA could lower is if you replace water (not by evaporation) or if the FC level gets low enough that bacteria can form, which naturally convert CYA to ammonia. Also, apparently very high FC levels can break down CYA.
 
JesseSchmidt said:
I was wondering if you lose CYA to evaporation. Mine was 50 and the last time I checked it a week ago, it was 40. I lose around 2-3" of water a week to evaporation right now. So does anyone know if the CYA goes with the water when evaporation happens?
Click to expand...
That sounds like a leak. If that is the case and you are refilling with tap water (CYA of 0) that would explain your slow loss.
 
NSBFAN said:
I was going to start another thread on CYA going down as mine has as well to even a larger extent but I've been trying to research all the threads out there first to not be redundant. It does seem to go down despite no obvious reason like draining or excessive rain.
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Mine has gone down too. The only thing we've had to do is to add water since we haven't really had any rain here lately.
 
I have had no splash out, I'm the owner/lifeguard when guests come over and not witnessed any. :)
That and the way my coping is it would take a car dropping from the sky to have splash out.

My water has been 85 degrees for about a week.

The only other factor is the neighbors red pine drops tons of those orange/brown elbow macaroni shaped
pollen nodules. I wonder if there is something in them that eats cya?

I've done the cya test enough times (and have the 50ppm test solution) to know I have lost 30 CYA over 2 months.
I just added more cya and back at 50 now.
 
I was literally just wondering this today. Mine was 80 45 days ago and now it is 50. My pool temp is heated and is 88 during day. Perhaps averages 85. Likely caused degradation if other thread is correct. I don't have a lot of splash out- certainly not that much.
 
frbruno64 said:
Just brainstorming here. Is stabilizer identical in quality and composition? Since we are seeing a large number of CYA questions from experienced members, maybe there is variability in stabilizer behavior across manufacturers. Sort of a Good Witch vs Bad Witch situation.
Click to expand...

i have been using the liquid $$ conditioner. I do loose around 1/4" of water every 1-2 days. Pool temp is a refreshing 94 degrees lol..
 
I can add I've done zero back washes.

Also, I finally test my CH. It was 250 ppm when cya was 50 and 2 months later is still 250 ppm.

That would have gone down had I backwashed a few times. (it has in the past)

So I definitely have some odd condition where my pool consumes 30 ppm of cya every 2 months.

I have always used the 4lb container of chlorox stabilizer granules on amazon.
This is my first season with this pool.

Figured I would just post this all here instead of a new thread since most
of us here have the mystery of cya going down.
 

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