Lost CYA

xyz

Gold Supporter
Sep 8, 2016
641
Escondido/CA
I had to turn up my SCG all the way up, and should not have to.

My TFP SWG pool was at 70 CYA last year, and has, in fact, been 100% trouble free and crystal clear.


So I checked my CYA level for giggles, but I was under the assumption you can’t lose CYA unless you lose water, which I have not.

CYA showed as below 30! It was stable all last year at 70. Can CYA Just disappear?

I bought brand new reagents and the test still show d belo 30.

Is there any chemical reaction that is somehow normal that eats CYA?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,543
Laughlin, NV
CYA slowly oxidizes from chlorine and UV. Normal is 3-5 ppm per month. Here in the desert, I can see up to 15 ppm loss in summer.

You should test your CYA each month.

Take care.
 

borjis

LifeTime Supporter
Aug 19, 2014
3,284
Pacific NW
For the record, I lose CYA every season.

I plug the equipment drains, add chlorine, check levels on the first weekend of march.

Over winter I lose 20 ppm CYA. Now, granted I have to drain off rain fill, so that makes sense.
we get a LOT of rain over winter.

But this other mystery loss occurs as well, some time between early march when I get the CYA to 50
and early June I lose another 30ppm. I get loads of red pine pollen in my pool from my neighbors tree.
It could be something else I suppose. It's not the rain though, I might drain 3-5 inches of water during
this time but nothing like winter when feet of water are drained, inches at time over several months.

But year after year I lose 30ppm in the spring and have to get it back up to 50. It will sit here
for the remainder of summer, at 50ppm until next March.

I don't know why, but it does.
 

xyz

Gold Supporter
Sep 8, 2016
641
Escondido/CA
CYA slowly oxidizes from chlorine and UV. Normal is 3-5 ppm per month. Here in the desert, I can see up to 15 ppm loss in summer.

You should test your CYA each month.

Take care.

OK, I knew I'd get a good answer here.

Thank you Marty!

Amazing how much less chlorine I need now that it is back to where it belongs.