What to look for that indicates your CYA Reagent has "Gone Bad"?

phappy

Well-known member
Aug 25, 2013
52
Hey all. Was hoping that some of our chemist-oriented brethren can assist with some info on this.

Yes, I admit...I have so far this season been using expired Cyanuric Acid Reagent. My question is...how can I tell if it has actually "gone bad"? When using it to test for CYA levels, does a "bad" reagent tend to give you HIGHER readings? LOWER readings?

I have tested using this expired CYA, and the result is "45", which is ideal for my pool.

BUT:
1.) I've noticed a LOT of chlorine usage. I'm putting in more daily than I ever have
2.) I took a water sample to Leslie (Found out they don't do the test kit CYA bottle/shake test anymore...ugh) and they use the testing cartridges. Their results showed CYA at 35. But not sure if I trust the cartridge tests.

I plan to purchase more/fresh CYA Reagent. Just interested in learning! Thanks for your help and replies.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,820
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
How old is your CYA reagent? It is pretty stable and if stored properly it can be good fro two to three years.

Your CYA is 50. If the dot disappears between 50 and 40 we round up and call it 50. You cannot eyeball values between the lines since he scale is logarithmic, not linear.

How much is a LOT of chlorine? A pool can use 2-4 ppm of FC a day.

What form are you adding chlorine?

Post specific FC tests and chlorine additions or share your PoolMath logs.
 

phappy

Well-known member
Aug 25, 2013
52
Ajw22, thanks for your great reply!

The CYA Reagent has been stored properly, room temp/or cool, not in direct sunlight ever. The label says it expired 4/2019.

Ah, ok. Yes..it would be 50 then. I had forgotten that it is best to round up.

For me, and my pool...since I've moved to the TFP method (I use liquid 12.5% Sodium Hypo) four years ago...the most I've been adding daily is this year. Today for instance, the test said I needed to add 4ppm!

It tested at 2pmm, and Pool Math says my recommended is 6 pmm.

It's just odd to me that for some reason....this year's season...seems to be requiring more chlorine.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,820
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Are you testing your FC 30 minutes after you add LC to know what you actually raised your FC to?

You could be getting weaker strength LC this year then last.

Do you check the date codes on your LC?


At CYA 50 your minimum FC is 4 and your target is 6-8. You should not let your FC drop below the minimum. If you are losing 4 ppm of FC a day then your target should be 8 ppm. See FC/CYA Chart
 
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phappy

Well-known member
Aug 25, 2013
52
Hi Ajw22,

- No, I have not done that. But that's a great idea. I'll do it tomorrow to see what I'm actually raising the FC to (half hour after adding it)
- In the past I've tested the strength of my CL, and perhaps I should do it again. Good thought!
- The dates is May 19 on the liquid FC I have. It was the most recently made date available at the time.

- Yes, I have been adding enough (or at least I have thought I've been adding enough, following the Pool Math results) to get up to 6ppm. But I'll check the FC/CYA Chart regarding what you said about losing 4ppm a day.

Thanks so much for your thoughtful replies & help, ajw22.
 

phappy

Well-known member
Aug 25, 2013
52
Well, I performed the overnight chlorine loss test per your suggestion Mdrgger88.

No change/decrease in FC at all! I ran the pump for thirty minutes, collected the sample and it tested at 4ppm. Same drill done this morning, and it also tested at 4 ppm.

I'm going to check/test the chlorine next.
 
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