CYA went down when I added Cyanuric Acid ??

kwwjnwjhw

Platinum Supporter
Jul 5, 2015
8
Peachtree City, GA
I have had my pool for about 5 years and have successfully maintained the chemicals until now.
On Oct 17, 2021 I had
PH = 7.9
TA = 60
CH = 400
CYA = 50
CC = 5
Salt = 3000
I used the troublefreepool calculator and it told me to add 10 cups of Cyanuric Acid and I did.

Oct 25, 2021 I had
PH = 8.0
TA = 70
CH = 375
CYA = 0 (totally clear and never hid black dot at all)
CC = medium orange (not on the yellow spectrum)
Salt = 3000

I expected the Cyanuric Acid to increase my CYA from 50 to 70 but it seems to have eliminate it or made the test inaccurate - not sure. The pool water is crystal clear. When I use the pool calculator it shows me that lowering my PH will take my overall score too low so I'm afraid to lower my PH but I also don't want it to get much higher. What should I do at this point?
 

Mdragger88

Bronze Supporter
Jun 1, 2018
3,330
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Has your water temp lowered? Bring your sample to room temp & test again. I suspect testing error.
How did u add the cya? Was it liquid or granular? If it was liquid & the bottle wasn’t mixed well the actual cya may still be in the bottle- it’s recommended to use the entire bottle & rinse it in the pool for this reason.
If it was granular cya the sock method is recommended so it gets dispersed directly into the water column. If it is poured into the skimmer it will just sit there in the filter media undissolved - this can also lead to clogs.
To test fc & cc you should be using the fas/dpd test for accuracy. The oto test isn’t very accurate- it only tests total chlorine which is free chlorine + combined chlorine. It doesn’t differentiate between the two. It’s more of a “do i have any chlorine or not” kind of test.
As for the ph let it ride in the high 7’s - 7.8/7.9 - as the water temp lowers the csi will lower as well.
 

kwwjnwjhw

Platinum Supporter
Jul 5, 2015
8
Peachtree City, GA
Has your water temp lowered? Bring your sample to room temp & test again. I suspect testing error.
How did u add the cya? Was it liquid or granular? If it was liquid & the bottle wasn’t mixed well the actual cya may still be in the bottle- it’s recommended to use the entire bottle & rinse it in the pool for this reason.
If it was granular cya the sock method is recommended so it gets dispersed directly into the water column. If it is poured into the skimmer it will just sit there in the filter media undissolved - this can also lead to clogs.
To test fc & cc you should be using the fas/dpd test for accuracy. The oto test isn’t very accurate- it only tests total chlorine which is free chlorine + combined chlorine. It doesn’t differentiate between the two. It’s more of a “do i have any chlorine or not” kind of test.
As for the ph let it ride in the high 7’s - 7.8/7.9 - as the water temp lowers the csi will lower as well.
Water has gotten cooler recently - from 75 to 64 in 10 days or so. I used granular. Put it in skimmer sock and put in skimmer for 2 hours and then messaged it until it was all gone from the skimmer sock. I'll get the fas/dpd test - I didn't like the one that came with my TF-100 kit anyway. I'll also try a room temperature test. Thanks for your response.
 

Bperry

Gold Supporter
Aug 20, 2020
1,071
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
My TF-100 kit has the fas/dpd test but I had forgotten this. I just did the test and I got 14.5 FC and 2 CC. Can I safely add a little acid to lower my 8.0 PH reading? Should I be concerned about these FC/CC values?
Does that mean it took 4 drops to turn the pink sample clear again after you added the 5 drops of “cc” test juice? You multiply those drops by 0.5 as well. If it only took two drops then your CC is 1.0. Figured it was worth double checking that since 2 is really high.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
3,330
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
My TF-100 kit has the fas/dpd test but I had forgotten this. I just did the test and I got 14.5 FC and 2 CC. Can I safely add a little acid to lower my 8.0 PH reading? Should I be concerned about these FC/CC values?
Ph readings are inaccurate at fc levels above 10ppm. They can show falsely high.
I would not adjust it now.
Wait until fc drops to 10 or below & test ph again.
 

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