Whatth the heck is happening to my CYA?

[Deb04]

Last week I had water tested at a pool store.

CYA = 30.
TA = 163
FC = 10
pH = 7.6

I came home and added CYA (dry, in the skimmer) and pH Minus and turned the returns so that they would bubble. I also turned down the SWG to 20%. 2 days later I tested with a Taylor-2006 and the

CYA = 45
TA = 175
FC = 8
pH= 6.8

I turned the SWG off. I kept the returns bubbling and it rained a lot during the week. So I figured the water had to be better today. Went to the pool store this moring and

CYA = 20
TA = 153
FC = 8
pH= 7.3

So, I'm OK with the pH, I can live with the TA for now, but why would my CYA DROP?! And why won't my FC go down.

It is sunny today for the first time in a week. I have the solar cover off, the bubbles on, and the SWG off. Hoping to burn some FC.

Any advice? Thanks.

 

[JasonLion]

Pool store water tests results are frequently unreliable. If you go to five different stores you will get five different results. Often, if you go to the same store on five different days you will get five different results. The differences in the CYA readings are fairly small, well within the range of variation you might expect from a pool store.

If you want to lower the FC level, have you tried turning down the percentage on the SWG?

 

[billybrobob]

Get your own test kit. TF100 or Taylor 2006.

 

[Butterfly]

Hi Deb, I would trust your test #'s from your Taylor 2006 over the pool store.

Please go to Pool School (link in my sig & in the sub-heading of each page)and read the article on "Water Balance for SWGs" for additional information. The recommended pH level for a SWG is 7.5 to 7.8.

 

[Guest]

So, I'm OK with the pH, I can live with the TA for now, but why would my CYA DROP?!
Testing error, do your own testing and don't try and compare tests done by different people with diffrerent testing sytems (I bet the pool store dos not use Taylor testing but possibly LaMotte?)

And why won't my FC go down.
You haven't had a chlorine demand to use it up.
It is sunny today for the first time in a week. I have the solar cover off, the bubbles on, and the SWG off. Hoping to burn some FC.

Any advice? Thanks.

Your TA is WAY too high still as is your pH....Instead of dry acid you might find that muriatic acid is cheaper and faster in lowering your TA.

 

[Deb04]

I tested with my Taylor 2006 and matched the pool store numbers on everything except CYA. I tested at 85. That makes a lot more sense. It was 45 last week. I'm guess that it was caught up in the filter and dissolved over the week.

I feel better.

 

[DLSDO]

CYA 20 @ PS
CYA 85 @ home test

Huge discrepancy....stay away from the pool store for testing if possible...so darn inaccurate