CYA dropping and trying to understand it.

[lovingHDTV]

My pool numbers are;

FC 4.0
TC 4.0
TA 80
CYA 50
PH 7.2
CH 650

My fill water has a CH of 200 and a TA of 220. As I add water , I also have to add acid to reduce the TA or I get a run away PH increase. Currently I just reduced my TA from 110 to 80 so my PH has not fully recovered at this point. It will eventually get up to 7.8 where it will stay until I add more fill water.

The problem is that at the beginning of the season my CYA was at 60, I have only back washed my filter 1 time this season and after that back wash was when I measured the CYA. I have also added 4 - 5 pounds of CYA this season as I'm trying to hit the recommended 70 for my SWG.

I have added CYA via a hose stocking in front of a return jet. I've added it immediately following my back washing directly to the skimmer. Last week I had 2 pounds of it dissolve in the stocking in 4 hours! I did not squeezing, squishing or anything, just hung it in front of the return jet.

By my calculations I've added enough CYA to get my CYA to ~90, but I'm still stuck at 50.

So a couple questions, I bought my CYA last year so it is ~1 year old, does it go bad in a year? Though it is all gone now and I just bought some more. Can my TA reduction (which happens every couple of weeks depending on rain fall and the need for fill water) be reducing my CYA also? I know that the common thinking is that you cannot get rid of CYA except with a partial refill, but I can't seem to get my CYA up and keep it up.

I don't have an automatic refill on my pool, and I'm only putting about 1.5 inches of water per week in my pool, so I don't think it is leaking out anywhere.

I'm about ready to start using dichlor as it is acidic and adds CYA to augment my SWG instead of bleach. I seem to be added both acid and CYA separately anyway.

Ideas anyone?

dave

 

[duraleigh]

I'm about ready to start using dichlor as it is acidic and adds CYA to augment my SWG instead of bleach.

Understanding and taking advantage of the effects of different products is what BBB is really all about. That sounds like a plan to me.

I can offer no explanation whatsoever for your CYA loss.

 

[gyoungers]

Hello HD,

I'm just north of you in the Dallas area and I must say that the issue I've had this year (also my first year) is very similar to yours.

I've checked everything I can think of... from leaks to possible bad CYA. All to no avail. I received new CYA reagent (which I didn't think was the problem) and I'm still testing 45-50ppm CYA today.

My post is here FWIW: cya-and-fc-problem-t7443.html

Please let us know if you happen to find a answer.

 

[chem geek]

I don't have any explanation for the dropping CYA either, but you are right that using Dichlor will be both net acidic (when accounting for chlorine usage) and for every 10 ppm FC that it adds it will increase CYA by 9 ppm. So be careful with how much you use, but that's what BBB is all about -- knowing how to maintain your pool regardless of which chemicals you choose to use.

 

[duraleigh]

Hi, Dave,

Why not switch for a while to tri-chlor pucks? Di-chlor really dumps a lot of CYA....I think you'd be in more control with pucks..

T/A reduction, or 1 year old CYA should have no affect on the amount of CYA in your pool......I'm at a loss to explain that but tri-chlor sounds like it might fit your situation well.