CYA increasing on its own?

Stacerp

New member
May 19, 2020
4
Sioux Falls, SD
My CYA is at 90 today, maybe closer to 100. A few days ago at 70. The week before, 60. I haven’t added any stabilizer for a few weeks. I thought it would only increase with the addition of stabilizer? I’m using the Taylor DPD test kit. Have an above ground 10,000 gallon pool with an Intex 2150 GPH pump & SWG with glass media. Run the pump 24/7.
FC 7.5
CC 0
PH 7.8
TA 80
CH 200
Salt 3250
Temp 70° (at 8am, has been around 80° until 2 days ago)
 

Brett S

Well-known member
Mar 15, 2019
703
Orlando
What are you using to chlorinate your pool? If you use tablets (which are likely trichlor) then that will add CYA to your water. If you use granular shock then that could be trichlor as well and that will also add CYA.
 

Stacerp

New member
May 19, 2020
4
Sioux Falls, SD
It’s a SWG. Intex 2150 GPH pump & SWG with glass media. Run the pump 24/7. I’ve never shocked it. The only thing I’ve ever added has been the salt, of course, stabilizer, and 31.45% muriatic acid (5 days ago and 19 days ago).
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,529
Laughlin, NV
Then there is a testing error.

How much stabilizer did you add? Since this a fresh fill, your CYA level can be calculated based on how much stabilizer you added and the volume of the pool.
 
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Stacerp

New member
May 19, 2020
4
Sioux Falls, SD
I added 2 lbs Clorox dry Chlorine Stabilizer two months ago and the same a month ago, based on what this app suggested. Only time I’ve added it Should it be going up this many days later? What do you mean by fresh fill? Pool was first filled/opened the end of May. I have tested almost daily so I feel like I have a pretty good handle on the testing, but maybe I’m doing something wrong? I rinse the bottle a few times after each testing but maybe some residual is etching into the plastic & screwing up the results - could that be possible? Thanks for your help, by the way!
 

Brett S

Well-known member
Mar 15, 2019
703
Orlando
Yeah, it does seem like it must be testing error. If this is new water and you have literally only added 4 pounds of stabilizer to it, then your CYA can’t be any higher than 48. (According to poolmath, 4 pounds of stabilizer in 10,000 gallons of water will raise CYA by 48). And I would expect it to even be slightly less than that, due to splash out and such.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
1,158
Hernando, Ms
It changes the 4lb addition from 48 to about 55. On a fresh fill . Meaning u had no cya to begin with.
be sure to to do the test in full sun w/your back to the sun. I also pour the mixture back in the little squirt bottle & read it again( I do this several times) & kinda average the results.
Try not to stare at the dot - fill to 30 then glance, 40 - glance etc