CYA tests very different, which to believe?

[Squidward Tentacles]

Hi,
Been following TFP since getting my first pool in 2017. Never had an issue with chemistry until now. I have always used the "tube with the black dot" CYA test and it's always been between 30-40. This year I tried using strips to test for the first time and 2 different brands of strips are giving me the following readings:
Ph 7.2
FC 3
TA 90
CYA 150-300
So I got out my drop tests and tube with the black dot and all of the other test results are consistent with the strips except the CYA is 30 with the black dot test. Now I'm confused-is my CYA really 150-300 and I need to start draining or is it 30? Any clues appreciated.
Squidward
13700 gal in ground fiberglass. Full sun, no shade. Ohio, USA
In line automatic chlorinator-use 3" trichlor pucks.
Pentair cartridge filter 150 sq ft.
Pentair Superflo 3/4 HP pump run 24/7.

 

[wireform]

I'd say trust your black dot test but just to be sure give us your step by step on your CYA testing.

 

[Newdude]

They're called guess strips for a reason. And *if* they were even close to correct, they're so vague it doesn't help. Look at the CYA values as an example. We need to know CYA to a 10. 0, 30 to 50, 100, 200, 300 doesn't tell us squat.

 

[Rancho Cost-a-Lotta]

How old is your test kit? If your primary means of chlorination is trichlor, I'd bet your CYA is well over 30 ppm.

 

[Squidward Tentacles]

Hello,
Thanks for the replies. My test kit is brand new. Expires 1/2026. My CYA test method is to fill the tube to the letter A with pool water, fill to letter B with reagent, mix for 30 seconds, allow to settle 2 minutes then pull the stick up while looking straight down he tube until you see the black dot on the bottom of the stick. Then look at the number on the stick to tell the CYA level. See pictures below. The test strips I'm using are AquaCheck and In the Swim brands both good until 2026. I just opened the pool about 3 weeks ago and used the In the Swim deluxe startup kit pictured below. I have only used liquid chlorine since opening.



Squidward

 

[Griswald]

Here's the thing...you state that the strips are good until 2026. That is incorrect, they expire in 2026, they are NEVER good.

 

[ajw22]

Toss the test strips into the trash and move on.

 

[Homebrewale]

If you are concerned about your reagents or testing procedures, you could purchase a standard solution from TFtestkits.

R-7065 CYA Standard 50ppm (2oz)

 

[Squidward Tentacles]

If you are concerned about your reagents or testing procedures, you could purchase a standard solution from TFtestkits.

R-7065 CYA Standard 50ppm (2oz)

Thank you very much! I just ordered it.