Still losing cya and I'm baffled!

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LaVergneL

0
Apr 3, 2017
8
Pollock, LA
I posted a month ago or so about this issue, and after the answers I got I brushed it off as a fluke but it's still happening.
Went from cya of 50 to 5 in a month.
I have not had much water loss. We havent had any rain so I've not had to drain. I've only had to backwash once during that time, and I use glass media so it's only 90 seconds to backwash and rinse.
It was discussed on my last post that some cya is lost to oxidation from chlorine and high temps, but after some research even if it happened this shouldn't have been more than about 10ppm at most.
I know there is a bacteria that can convert cya to ammonia, but I just did an ammonia test this morning and it was 0.25ppm. We actually finally had a downpour yesterday which is what made me do a full test today, and I'm assuming ammonia that low could be from the rain. Definitely not anywhere near high enough to say that's where my cya went.
My question is this...does anyone else use a DE system, or zeolite or glass media in a sand filter something that filters the tiniest particles and have this happen? I read about the new cya removers that basically filter it out, and I know it's debatable whether that even works, but if it CAN be filtered out is this what's happening? I've had this problem ever since I switched to glass media. Or is there some other possibility that I'm overlooking entirely?
 
Donldson said:
How are you testing your water?
Click to expand...
I get a pool store test once a month. I also confirmed the 50 reading at home with Taylor R-0013 cya reagent, and I tried to repeat it today and it's not registering at all so I take that as confirmation of the 5 reading from pool store test. I genuinely do not believe that the testing is the issue. This is also not the first time it has happened.
 
I suspect its not 5ppm but that it is below a readable value. Depending upon which tube you use that could be a little less than 30 or a little less than 20.
What are all your other test results? (from your kit)
Also - how are you adding your cya & what product are you using?
 
LaVergneL said:
I know there is a bacteria that can convert cya to ammonia, but I just did an ammonia test this morning and it was 0.25ppm. We actually finally had a downpour yesterday which is what made me do a full test today, and I'm assuming ammonia that low could be from the rain. Definitely not anywhere near high enough to say that's where my cya went.
Click to expand...

It’s not ammonia conversion. Bacterial conversion of CYA to ammonia is a multi-stage process that absolutely cannot happen in a swimming pool if there is any measurable amount of chlorine in the water. The bacteria responsible for converting CYA to ammonia are highly susceptible to chlorine disinfection. Ammonia tests also cannot work when the water is chlorinated as ammonia and chlorine instantly react with one another. So the ammonia number you are seeing is just a false low reading on the test. It’s not real.

As for filtering out CYA, that’s not possible either. CYA is a fully dissolved chemical compound. There is no mechanical filter that can remove it. As for the CYA reducers, those are mostly junk. Basically snake oil.

I do believe you have a CYA loss, but I doubt it has anything to do with your glass media. As @Mdragger88 asked - please post your other chemical levels.

How do you chlorinate your pool?
 
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Mdragger88 said:
I suspect its not 5ppm but that it is below a readable value. Depending upon which tube you use that could be a little less than 30 or a little less than 20.
What are all your other test results? (from your kit)
Also - how are you adding your cya & what product are you using?
Click to expand...
I only use liquid chlorine, except when I need to bump up my cya then I switch to dichlor granules until it's back up. Normally I aim for 50ish, then test once a month and when it's gone down to 30 I calculate how many bags of dichlor I can go through before it's 50 ish and repeat. I hadn't tested the cya myself until today since my last pool store test, since I haven't had to lose any water I assumed I would still be good during that month.
 
JoyfulNoise said:
It’s not ammonia conversion. Bacterial conversion of CYA to ammonia is a multi-stage process that absolutely cannot happen in a swimming pool if there is any measurable amount of chlorine in the water. The bacteria responsible for converting CYA to ammonia are highly susceptible to chlorine disinfection. Ammonia tests also cannot work when the water is chlorinated as ammonia and chlorine instantly react with one another. So the ammonia number you are seeing is just a false low reading on the test. It’s not real.

As for filtering out CYA, that’s not possible either. CYA is a fully dissolved chemical compound. There is no mechanical filter that can remove it. As for the CYA reducers, those are mostly junk. Basically snake oil.

I do believe you have a CYA loss, but I doubt it has anything to do with your glass media. As @Mdragger88 asked - please post your other chemical levels.

How do you chlorinate your pool?
Click to expand...
As of this morning
Alkalinity is 80
pH 7.5
Fc 4
Cya didn't register, pool store test said 5

I'm currently using hth 6 way drop test kit but it comes with very little cya reagent so I'm using Taylor R-0013 for that. I don't remember exactly what my chlorine was with pool store test, but it wasn't alarming and no combined chlorine. I don't usually pay attention to calcium phosphates etc, but as a side note just in case my calcium stays low too, I want to say it was around 50.

I have always used liquid chlorine, except when I need to bump up cya then I just switch to dichlor for a short time. According to the popl math app each bag bumps up my cya 4ppm, so it doesn't take long. Normally I get a pool store test once a month so I just go by that and calculate it to 50ish and that has always worked out for me. It's normally gone down very little in between but now for some reason between my tests it's going to almost nothing.
 
Are you using 99% dichlor or is it a lesser % ?
PoolMath assumes 99% so if its less than that your cya rise wouldn’t be as high as calculated.
As water temps rise above 90 degrees the rate of cya degradation increases too.
Don’t put alot of stock in the pool store cya results- they’re wrong more than right.
For now you need some cya.
Add 10ppm worth of granular cya via the sock method & retest in 24hrs. Repeat as necessary until you have a readable cya.
Going forward use your cya turbidity test weekly and adjust cya as needed.
 
Do you have an autofill or are you filling manually? What are your calcium hardness readings during the same period? What is your fill water CH?
 
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