Need help getting pool chemistry back in order. CYA, TA, and pH are out of wack

mavrick6382

Member
Apr 14, 2017
14
Cave Creek, AZ
Hey all,

Historically I have been a tab user. However, in summer of 2018 I had a major algae bloom. Due to a hectic work travel schedule, vacations, etc. I failed to treat it properly (clean filter cartridges, SLAM, etc.) and instead kept feeding the pool tabs thinking more chlorine would do the trick (stupid and lazy on my part). This resulted in a spike in CYA which forced me to drain the pool, re-fill, and add stabilizer to get my CYA back in check. I got chemistry back to normal and I finally decided to make the switch to liquid chlorine. Had no issues from October 2018 until the last 2 months or so. Basically I started noticing my pH was always high and the pool seemed to be needing way too much chlorine; every day the pool was dropping from a FC of about 6 (tested in the morning before 7a) down to 1 or less within 12 hrs. At the height of the summer here in AZ (temps of 108-112) I assumed it was normal. But in the last 2 weeks the temps have dropped significantly (pool temp went from upper 80's to upper 77 degrees as of today) and I decided something was majorly off. The last couple of days I have been trying to drop the pH and it simply hasn't been dropping. Did a full chemical test today and here is where I am at:

FC = 1.0
pH = 8.0+
TA = 230
CYA = <30 (My Taylor K-2006 test kit only measures the CYA to 30. Basically I had the vile completely topped off and I could still clearly see the black dot. The CYA could very well be close to zero)

The high TA has kept a high pH, high pH is eating up chlorine. But what has caused the substantial drop in CYA? Had a recent rainstorm dump which visibly raised the water level, but that's it. Nobody has gone swimming in a couple of weeks. I thought by switching to liquid chlorine I'd avoid any big changes in CYA. What would you guys recommend I do as a next step? I have a 4lb bottle of granular Clorox stabilizer on hand. Should I add that to get my CYA in check first? According to Pool Math I need 71oz (4lbs) to get the CYA from 0 up to 30. Any help is appreciated. Hopefully I offered up the necessary info.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,404
Laughlin, NV
CYA degrades naturally. In normal temperature water in normal UV areas, it is usually 5ppm per month or so. In Arizona, you have elevated pool water temperatures and above normal UV impact. Both accelerate CYA degradation. I see 10-15 ppm CYA loss per month from May through August. So your CYA drop is not unexpected.

Test your CYA monthly. Use either granular CYA or a few pucks when you need to raise your CYA back to 50 ppm or so.

High pH does not eat chlorine. Low CYA does.
 

mavrick6382

Member
Apr 14, 2017
14
Cave Creek, AZ
Thanks Marty!! Probably ignorant of me to think CYA would stay level, clearly it does not. I'll be sure to do a full chem check at least monthly.

If I am trying to go from zero to 30 CYA (I am opting for 30 to start since I don't know the exact CYA level right now), based on Pool Math I need to add 68 oz by weight. A 3" tab is 8 oz, which equates to 8.5 tabs. Is that correct?