sky high CYA

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anuoldman

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Apr 10, 2011
15
new guy... pls be nice...

so for years I've got a grumpy expensive pool guy and then can him last Nov... I read up here some... get a dangerous level of knowledge and dive in...

1- time goes by and suddenly here in south fla the temp goes up and chlorine usage goes high quick...
2- yesterday a very very light amount of algae crops up and without testing CYA I shock 30ppm and run the pump 24hrs clean the filter and brush every 6hrs
3- water is crystal clear but there are very light, stubborn green patches on bottom that won't brush off.
4- pool store says shock to 80 to 'bleach the green stain' and I do... no effect after 5 hours
5- I finally check test strip and CYA is waaaay over scale high I would guess at least 200+

no kit till tomorrow... but test strip says:
(12K gallon in ground plaster, hayward 800 with 2hp pump)
CH: about 800
TC: >10
FC: >20
PH: busted cause of the chlorine
TA: 120
CYA: color is so off scale (150) high as to make me think it's 200+

I need this pool usable Thursday (60 hours from now), so should I :

A- drain 50% and refill then adjust
B- wait more for the huge shock to work on the faint green patches first
C- something else

?
 
OK, I'll start.......

Getting the kit is the correct move, which kit did you get? Once that comes in, please post a full set of results for the experts here to examine. If indeed your CYA is 200+, I am afraid to say that a partial drain and refill (a few of them) might be your only choice unless you have a reverse osmosis company in the area.

Whatever the problem is, have no fear, you have come to the right place.
 
if I wait till I get the kit to act as winger infers, I blow 20 of 60 hours... so I'm reluctant to do that... if CYA that high makes it 'impossible' to shock, even at 80ppm, then you are saying I should drain and refill NOW?
 
If you're assuming 80 will be your NEW CYA level is after a 1/2 drain/refill......then no, much more easily done.. Whole lotta difference between that and I guess your current guess of 160? Which is just a guess btw. This is why you might do MORE than one drain and fill to start. Fresh water is a lot easier (quicker) fix in your situation. Your current FC level of 20 is in NO WAY a super high shock level for what you have-----------not even close! See the chlorine/cya chart in pool school. You couldn't PAY me to shock my pool to an 80 FC level regardless what the pool store guy said. It will take longer than till Thursday for that to drop to a low enough level to swim in safely. Unless you like Blondes with brittle hair!
 
It's really your call and do you turst the PS test results? That's a lot of water to dump if CYA is really not that high. But if your water is cheap...go for it :goodjob:
 
city here will reduce the bill if its for the purpose of pool repair or refill....

--- my bad... pool store said add 80 ppm of chlorine... I did that 6 hours ago, but it didn't impact the very light green, non brushable patches
- I assume the CYA is above 150...

so the real question is... with CYA above 150, is that 80+ chlorine gonna accomplish anything or should I waste the chlorine and refill now?

my assumption is that I'll replace 75% of the water and test
 
Don't have too much faith in the test strips made this mistake last year myself. Test strips are notoriously inaccurate for high numbers if FC and CYA. You may find that once your kit arrives that it's at much more workable numbers.

What are you using for your source of chlorine? I would do as Woody suggested and start off with pool school and then more suggestions can probably be made with a good idea of what's been used in the pool and for how long.

Sent from my Evo4g using Tapatalk.
 
the chlorine is definitely sky high... 8 gal of 10% liquid in a 12Kgal raises by nearly 80ppm by itself plus what residual and I just did it

the CYA is so hard off scale high that it's for sure above the strip 150 limit....

so given the time issue, and the green stain issue, I'd like to let the chlorine that's in there work before the water change to avoid a second shock... but if the high CYA is FOR SURE preventing it from working... I'll change the water now...

test strip below, from top:
CH: between 250-1000
TC: off scale high >10
FC: waayyyy off scale high >10
BR: na
PH: broken
TA: between 120-180
CYA: wwwaaaaaayyyyyy off scale high >150
 

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Make a solution containing 3 parts tap water and 1 part pool water and then test that for cyanuric acid. Multiply the result by 4. This should give you a better idea what your cyanuric acid level is.
 
ok... I diluted the pool water to 25% and multiplied to come up with :
CH: 400
TC: 40
FC: 80
BR: na
PH: broken
TA: 160
CYA: 200

to be clear... the goal is not to lower CYA... obviously I can do that...

the goal is: get rid of the faint green patches / algae that isn't brush-able and have a pool that humans can go in 59 hours from now....
 
You started draining yet???????????????????
......and forget your assumption of a "second" shock. You haven't truly shocked it the first time yet. THAT'S the whole problem! Write off the chlorine expenditure loss.

You started draining yet???????????????
 
The dilution was just for the cyanuric acid test. You really need to lower the cyanuric acid to less than 80 ppm.

You need to be careful when draining and refilling. Don't drain the pool water to lower than the ground water and try to minimize the amount of direct sun on the plaster.
 
Assuming CYA is around 200, then shock level is around 75 to 80. Remember that test strips are quite imprecise and testing with dilution increases the lack of precision, so the CYA level could just as well be 150 or 300 or maybe even 400, as 200. If CYA is 300 then shock level is around 110 to 120. Also keep in mind that with very high CYA levels, the FC level is going to come down very very slowly. Assuming FC is currently 80, FC is still going to be 70 to 75 in 59 hours. I don't consider that swimmable, though some people might.

Sun on the plaster shouldn't be an issue at this time of year. That is usually only an issue in hot dry climates during the summer when the plaster can easily get very very hot in direct sunlight.
 
Thanks... I just went out to it again and during this convo, the green patches have faded about 75% so I'll let it ride a few more hours...

with CYA supporting FC so much, why not keep CYA at 100 and chlorine at 15 to reduce net chlorine usage? I saw another thread on this where the explanation was basically "because the level has to be higher" which is great, but who cares if it gets used very slowly?

what's the real negative to very high CYA?
 
"the FC level is going to come down very very slowly. Assuming FC is currently 80, FC is still going to be 70 to 75 in 59 hours. I don't consider that swimmable, though some people might."---per JasonLion.
...............................................I'd take his word for it!
 
There are several. One big problem is that it becomes very difficult to measure the PH, none of the common PH tests work when FC is above 15, and can be off even when FC is at 15. Another is that adding the dramatic amounts of chlorine required to shock tends to shift PH out of the safe range and then there is no easy way to measure it or correct it, which can be very problematic as shocking is either slower or doesn't work when PH is way out of range.

Another problem is that there is no way to reliably know what your CYA level really is when it is over 100. The error range on your CYA test results right now are something like -75 to +200. Even with a better test kit a CYA measurement around 200 is still going to be +-50 or +-60. With that kind of possible error you don't really know what your FC target should be and you either waste chlorine by keeping FC extra high or problems almost always ensue.
 
I just copied and pasted to a text file what Jason just gave as reasons NOT to have high CYA/FC levels. It will get printed out and added to my notebook------which is gettin' pretty thick thanks to this site! I do that whenever I see something that better explains something I don't know or might be of use to me later and I can refer back to.
 

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