pH & CYA increasing without intervention

[claryd]

Howdy!

Newbie to the site and to pool ownership here. I just want to understand the chemistry happening here. Back story: pool start-up yesterday at about 5p with MA, CA, and chlorine. Test results:

7/2 @ 2235:
FC 6.5, CC 0.5, pH <7.0, TA 90, CA 240, water temp 80

7/3 0800:
FC 6.0, CC <0.5, pH 7.0, TA 90, CA 240, CYA 62, water temp 78, SI -0.58

7/3 1545:
FC 4.5, CC (not checked), pH 7.2, CYA 66, water temp 82, SI -0.28

7/3 2020:
FC 4, CC <0.5, pH 7.4, TA 90, CA 240, CYA 68, water temp 82, SI -0.12

Now, I understand that the pH is going to increase particularly because it's a new pool, per Pool School's The ABC's of Pool Water Chemistry. What I'm trying to wrap my head around is the increasing CYA level. I'm not adding CYA. I didn't even think that the PB used chlorine w/ CYA yesterday but there it is! It came from somewhere. The pool has been used today for a couple of hours. I'm not understanding why my CYA levels are increasing without adding any. Can someone help guide me, please?

 

[mknauss]

Welcome to the forum!

It is not possible to measure CYA at the resolution you show. The test vial is logarithmic. All the values you show for CYA are rounded up to 70.

Why do you want that high of CYA for a non-SWCG pool?

 

[frustratedpoolmom]

So CYA isn't really tested in such a specific number, a range of 10 or so is good enough... I'm not thinking there is anything there to worry about.

Your Calcium, alkalinity and ph levels will all change on their own as the surface cures. There's an article in pool school about startup of new plaster. I would just call the PB and ask him what product was used (the active ingredient).

And then have some POP (pool owner patience) and a beverage and enjoy your pool.

EDIT: Is it possible you are doing the CYA test incorrectly? Hold off on testing it again for now, save your reagent.

Here is a link on performing the test correctly: https://www.troublefreepool.com/images/global/CYA%20EndPoint.png

And In Pool School - go to the Extended Kit Directions to read more about it.

 

[Richard320]

CYA is slow-dissolving. I suspect the PB did what the packaging says and poured the stuff down the skimmer. Now the granules are inside the filter dissolving, which is why the CYA keeps rising. It's probably close to done, now.

I also wouldn;t be alarmed if the CYA goes down. Right now it's coming out the returns and circulating through the skimmers. As it spreads to the further corners of the pool, it may go down.

 

[claryd]

mknauss, Thanks for your welcome and reply. See? Newbie! I didn't know to round up or down. Good to know. I don't want the CYA levels that high, hence my question.

frustratedpoolmom, lol; thanks! I'll definitely read the article on the pool startup. I'll also contact the PB to as what he used. Thanks!!

Richard320, PB did just that; or at least, he put SOMETHING in the skimmer. I didn't do good to ask what products he was using. Your info was super helpful! Thank you. Your response was the ah-ha moment. =) Thanks!

 

[claryd]

frustratedpoolmom, thank you for your edit. Yes, I'd been doing my test wrong; well, I'd been reading my levels wrong. Still elevated but reading wrong. Thank you. Richard320 nailed it and the next test was already a lower level.

Thanks, guys, for your help!!