Where did the CYA go from the tablets?

smackdab · May 30, 2015

When testing my CYA level I usually pour the the test liquid back in the bottle and recheck it a few times and am pretty consistant about where I see the dot every time.

On 5/13 I tested my CYA level and found it to be around 22 ppm. I added 2 lbs 6 oz of 99% Trichlor (All were 1" except for one 3" tab) to a floater and let it all dissolve to raise my CYA since I wanted to get rid of the tabs. All the 1" tabs dissolved 9 days ago but the 3" tab was stubborn and finished dissolving 4 days ago. This should have raised my CYA level to around 32 ppm according to PoolMath. I tested my CYA level today and it was around 25 ppm.

Where did it go? What happened? There has been no rain here to speak of so I know it wasn't diluted by rain or me adding fill water. The tabs did add FC but I couldnt say they added what they were supposed to.

chem geek · May 31, 2015

The test isn't that accurate so I wouldn't conclude that there's anything missing. Some Trichlor pucks aren't all Trichlor and have some other ingredients, though usually not more than 5%.

When you add more CYA in larger quantities from Trichlor, then it should be more noticeable.

Texas Splash · May 31, 2015

That does seem a bit odd, but another reason why we don't rely on tablets that much. Still, it sounds like you were just trying to get rid of them. No harm done, and you seem to understand CYA testing well. If after they're all gone you still need to increase the CYA, you can pick-up some granule stabilizer and will probably have better results.

jblizzle · May 31, 2015

I think you are just within the noise/accuracy of the test.

smackdab · May 31, 2015

Ah ok. Yes I just wanted them gone. They've been sitting on my bench for at least 2 years and I was tired of looking at them. Actually I have a bottle of Stabilizer that is at least 3 years old and I added some of it to make up the difference so I'll retest in a week or so. I was just wondering why my numbers didn't line up.

Yev · May 31, 2015

Not sure about if the 3" tab amount really makes a difference, but I thought that someone said that adding CYA takes 2 weeks or longer to be able to be measurable. IF that is a true statement,and the 3" tabe just dissolved completely 4 days ago, there could be a measurement lag time issue.

jblizzle · May 31, 2015

The CYA from Trichlor and Dichlor should show up in the test very quickly after dissolving. The granular CYA may take up to a week to show on the test.