CYA still present after complete drain and refill

cbj_atx

New member
Mar 31, 2021
4
Austin, TX
CYA was so high that the black dot in my test kit disappeared after 1 drop so who knows.... 500+? We've only had the pool for 7 months. Was previously serviced by the past owners who exclusively used dichlor products since the pool was installed in 2011. I do not know if the water has ever been fully replaced.

Sooo I drained and refilled over the last 24 hours. Was able to remove about 95% of the water with a gas powered pump and took the opportunity to also clean tiles, filter cartridges and hose down and scrub the entire pool surface. Just got everything up and running and here's my result:

FC: 8.6
CC: 0
pH: 7.8
TA: 90
CH: 200
CYA: 65 (ugh!)
Water Temp: 73
CSI: -0.12

Is the 65 CYA still problematic? It's obviously a significant improvement over the before number but curious to get some additional thoughts here. Not super interested in draining/refilling again anytime soon.

TIA!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
cbj, you can live with that new CYA. Seeing as how we're about to get lit-up with temps in the 100s this week, it should help. Now just be sure to use liquid chlorine only and keep the FC balanced to that CYA as noted on the FC/CYA Chart. Other than that, I think you have a good handle on things. Good job! :goodjob:
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,077
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
CYA does not leach out of the plaster. What is in the water is what was left in the pool.
 

JamesW

TFP Expert
Mar 2, 2011
24,016
Possibly some cyanuric acid left on the walls if the walls were not rinsed off.

I have heard that cyanuric acid/cyanurate can form scale on plaster walls, but I don't know if it's true.

Most likely, it's just what was in the water that wasn't drained out.
 

cbj_atx

New member
Mar 31, 2021
4
Austin, TX
Yeah, I rinsed all the equipment and the walls and all equipment and filters. Also scrubbed tiles then rinsed again and kept draining. I only had about 18 inches left in deep end of pool so it's WILD to think that CYA was that high. I'll tell you, it was a pain in the arse but the pool has never looked better than it does today. I've been reading more on the subject and since I'm in such a hot, sunny climate, seems like my 65 CYA is acceptable. Just need to be cautious to stick to liquid chlorine only.

Thanks all!
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,077
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Since you just refilled, I would suggest testing CYA again after several days. Complete mixing can take some time.
 
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red-beard

Gold Supporter
May 27, 2019
937
Houston, TX
Pool Size
25000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
Yeah, I rinsed all the equipment and the walls and all equipment and filters. Also scrubbed tiles then rinsed again and kept draining. I only had about 18 inches left in deep end of pool so it's WILD to think that CYA was that high. I'll tell you, it was a pain in the arse but the pool has never looked better than it does today. I've been reading more on the subject and since I'm in such a hot, sunny climate, seems like my 65 CYA is acceptable. Just need to be cautious to stick to liquid chlorine only.

Thanks all!
Yes, your CYA was that high. I used Trichlor tablets for almost 10 years without a drain. I expect my CYA was 750-1000 ppm.