Need help with CYA

Shaf77 · Jul 17, 2014

About 2 weeks ago, our CYA was at 30. I added 1.8Kg of stabilizer (from Walmart) and according to the calculator it should have brought it up by 27.

Tested today and CYA is at 40. I had a similar problem last year where I would add stabilizer as per the calc but it never got to what I would think it would. No backwash done.

Why would this be?

Aside from losing stab when a pool is drained, how else would one lose it?

zimm · Jul 17, 2014

Maybe your capacity calculation is off on the pool? Have you added any chlorine manually (besides your SWG)?

northrn · Jul 17, 2014

Evidently, I have reading comprehension problems today....never mind me.

:roll:

Shaf77 · Jul 17, 2014

Shaf77 said:
About 2 weeks ago, our CYA was at 30. I added 1.8Kg of stabilizer (from Walmart) and according to the calculator it should have brought it up by 27.

Tested today and CYA is at 40. I had a similar problem last year where I would add stabilizer as per the calc but it never got to what I would think it would. No backwash done.

Why would this be?

Aside from losing stab when a pool is drained, how else would one lose it?

I have added chlorine and that usually measures out fine...

ship of fools · Jul 17, 2014

My pool is 16 x 32 with a deep end. I have mine calculated at 21,000 gallons. If the conversion on the internet is accurate 65,500 is 17,000 gallons+- so maybe you are more than 65,500 liters??

Shaf77 · Jul 17, 2014

Here is the sizing and volume from the manufacturer...

17,300 US Gallons
14,500 Imp Gallons
65,500 Litres

Donldson · Jul 17, 2014

Because the CYA test is the most subjective and has the largest margin of error of all the tests it us quite pissible this was just a testing error. If your CYA was a bit lower than measured when you started and a bit higher than it measures now that would explain it.

The current CYA test is the most accurate available at a consumer level, even if very imperfect. Since the FAS-DPD is far more accurate, and your chlorine does what you calculate it should, then your pool size is likely correct. So treat your CYA as it reads and add more if you want it higher.

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