My CYA is creeping up and I don't know why

Mypool12 · Jun 25, 2023

FC 5.0, pH 7.6, Alk 60, CYA 60, CH 230, pool temperature 72 degrees

I hope everyone is having a great summer and enjoying their pool. I am just starting to run into a CYA problem.

At the beginning of the season (5/16) I tested my CYA and it was at 30. I tested CYA multiple times and confirmed it again the next day. My pool tests looked great through 5/31. At this time, I went away for a few days and put two pucks in my chlorinator, and had someone put into the pool 48 ozs of chlorine each day. When I returned, I took the remaining pucks out of the chlorinator. I only use the chlorinator when I go away. I did not check the CYA again until today. I was shocked to see that my CYA was now at 60!

I did notice that over the last few weeks, I was not using a lot of chlorine. I thought it was just the cooler weather in the east. The only other factor that I have been considering is that I have only used Walmart chlorine this year. The chlorine is called "Pool Essentials" with 10% sodium hypochlorite and 90% other ingredients. It was a lot cheaper than Home Depot. Could the Walmart chlorine have CYA in it like the pucks?

Can anybody else think of a reason why my CYA has been creeping upward?

Thank you for your help.

Mdragger88 · Jun 25, 2023

The walmart pool essentials liquid chlorine doesn’t contain cya.
Perhaps your initial testing was a bit off & you had more than you thought (cold water- below room temp can give falsely low results)
The cya reagent stays good for a long time but it does get old & can read a little off.
Did you perhaps use older reagent for the initial tests & new reagent for the more recent test?
The cya test is the hardest one to master so lets also be sure you’re being consistent with it .
I do mine in the same place outside at the same time of day every time as different lighting conditions affect what you see.
Wherever you do it be sure its the same conditions each time - bright light is best.

CYA - Cyanuric Acid Test

Cyanuric acid (CYA) is the chemical name for the product commonly called “pool water stabilizer” … Read more…

www.troublefreepool.com

Are you sure your helper didn’t add anything else to the pool?
Here’s what each 8oz puck does in your pool

HermanTX · Jun 25, 2023

It is best to let the pool water sample rise to room temperature if you are testing a very cold pool. I think the original test was a little off and since you only added 2 pucks which did a minimal increase in CYA. Maybe test your CYA again to ensure no testing error and go with that. Having a CYA of 60 is ideal when using LC.

Mypool12 · Jun 25, 2023

Mdragger88 said:
The walmart pool essentials liquid chlorine doesn’t contain cya.
Perhaps your initial testing was a bit off & you had more than you thought (cold water- below room temp can give falsely low results)
The cya reagent stays good for a long time but it does get old & can read a little off.
Did you perhaps use older reagent for the initial tests & new reagent for the more recent test?
The cya test is the hardest one to master so lets also be sure you’re being consistent with it .
I do mine in the same place outside at the same time of day every time as different lighting conditions affect what you see.
Wherever you do it be sure its the same conditions each time - bright light is best.

CYA - Cyanuric Acid Test

Cyanuric acid (CYA) is the chemical name for the product commonly called “pool water stabilizer” … Read more…

www.troublefreepool.com

Are you sure your helper didn’t add anything else to the pool?
Here’s what each 8oz puck does in your pool
View attachment 507483

Thank you for your response, Herman. I think the culprit might be the reagent. The old tests were done with older chemicals left over from last year. I opened up a new reagent for CYA today. The only concern that I have is that the pool was behaving properly until the last 2 weeks. I will test it more frequently and hopefully, it maintains its' level at 60.

Mypool12 · Jun 25, 2023

HermanTX said:
It is best to let the pool water sample rise to room temperature if you are testing a very cold pool. I think the original test was a little off and since you only added 2 pucks which did a minimal increase in CYA. Maybe test your CYA again to ensure no testing error and go with that. Having a CYA of 60 is ideal when using LC.

Thank you for your response.