Does CYA sink?

qbot

Member
Jun 8, 2010
18
Central WA
For reasons I will not get into here, I have no circulation from the main drain. I have just one skimmer and that's how the water circulates.

When I opened my pool this summer, my CYA level was 50 (pool store test). Since then, every couple days, I stick the vacuum head underwater and pull water from the deep end for circulation. I have not used any pucks since I opened and have strictly stuck to the BBB method. Now my CYA level is ~80 ppm.

I ask this question as someone who knows nothing about chemistry: Did the CYA sink to the deep end before I started circulating? How else to account for the increase without pucks?

Anyhow, these are my values. I appreciate any input:

FC 4.5
CC .5
pH 7.6
TA 100
CH 260
CYA 80

My FC has dropped recently. It was 3 ppm yesterday and I added 2 jugs of bleach. The pool calculator says I'm in my FC target, but the CYA/Chlorine chart says my target should be 9 ppm. Should one be given more weight?
 

Miranda

Well-known member
Jan 20, 2008
161
Northeast Florida
I wouldn't trust a pool store CYA test unless I personally witnessed the entire process, and even then I would have doubts. Firstly because the test is time consuming and the reagent is expensive, providing an incentive to skip the test and say they did it (out of sheer laziness), or even dilute the reagent with water to make it stretch farther. Secondly, because most pool stores promote stabilized chlorine as the holy grail and don't believe/refuse to acknowledge that too much CYA is a real problem. Because of this mindset, they don't think the test is very important, so why bother? The only incentive to test (or pretend to) is to report a low result and hopefully sell you more CYA, stabilized chlorine and pH up, or report an "in range" test so you won't ask them to do it again.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
I agree with Miranda, testing errors at the pool store are the most likely cause. Your CYA level has probably been stable, the question is which test is right, if either of them are. With CYA at 80, if your CYA really is 80, you want to keep FC at least at 6 all the time. Aiming for a target of 9 is good.
 

qbot

Member
Jun 8, 2010
18
Central WA
The numbers in the OP above are from yesterday. The consensus seems to be that I have to increase my FC. Question: If my FC is currently 4.5 ppm, how much bleach do I need to dump to get a minimum of 6 or target of 9?
 

poolnew-b

Well-known member
Jul 6, 2010
131
laconia, NH
qbot said:
The numbers in the OP above are from yesterday. The consensus seems to be that I have to increase my FC. Question: If my FC is currently 4.5 ppm, how much bleach do I need to dump to get a minimum of 6 or target of 9?
Using the pool calculator and assuming your pool is 23,000 gallons as stated in your signature.

You would need
1 gallon 2 quarts 3 cups or 2.2 (96 oz) jugs
to raise it from 4.5 to 9
 

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