HIGH CYA=HIGH SLAM and high Ph. Help!

PhotoBug

Well-known member
May 25, 2017
117
Erial, NJ
Hi All! My DH decided he wanted to use pool store Crud this year……for the last 3 summers he was traveling and I followed all advice here and had a stunning crystal clear pool.

Needless to say, our CYA was over 100. after showing him this forum and some posts, he finally agreed to stop using that junk! So back at it I went. Pool developed algae and now is super cloudy. I drained about 1/3 of the pool and got CYA down to 70. We are approaching the end of the season so I thought that would be ok…….

Here are my numbers as of this morning…..

FC 15
CC .5
TA 110
PH 8.2
CH 25

For the last few days, I’ve been doing SLAM but worried that an FC of 28 based on CYA is too much and I think PH is high due to high FC NUMBERS

Im not sure what to do? I’d rather not dump more water. Should I continue SLAM or lower ph or both? I’m at a loss and he is less confident once again. Please advise!

julie
 
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BowserB

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At CYA of 70, SLAM free chlorine is 28ppm. See here:
Also, as I recall, pH measurement may not be accurate at high FC levels, so if you can find enough chlorine, SLAM probably is your first priority. Also keep in mind target chlorine at CYA of 70 is 8-10ppm, so you might decide to dump more water at some point. I normally lose CYA over the winter, but down here we don't close pools, so your experience may be different.
 

PhotoBug

Well-known member
May 25, 2017
117
Erial, NJ
At CYA of 70, SLAM free chlorine is 28ppm. See here:
Also, as I recall, pH measurement may not be accurate at high FC levels, so if you can find enough chlorine, SLAM probably is your first priority. Also keep in mind target chlorine at CYA of 70 is 8-10ppm, so you might decide to dump more water at some point. I normally lose CYA over the winter, but down here we don't close pools, so your experience may be different.
Thank you. Yes I’m aware of FC level for SLAM is 28. That just seems so high. In your opinion, is that ok and should I not worry abouT ph until slam is done?
 

mknauss

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May 3, 2014
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Im not sure what to do? I’d rather not dump more water. Should I continue SLAM or lower ph or both? I’m at a loss and he is less confident once again.
As Bill said, follow the SLAM Process. ph test is invalid above a FC of 10 ppm.

Your pH tested at 7.3 a couple weeks ago. I doubt it is very high.
 

Newdude

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Jun 16, 2019
10,833
NY
Yes I’m aware of FC level for SLAM is 28. That just seems so high
It’s only high if you don’t believe the CYA relationship.

But you understand the CYA buffers the FC so it’s all good.

You should get about 3ft of off season rain / melters snow so you can easily limp along for the rest of this year maintaining a higher (but *not* ‘high’) FC per the FC/CYA Chart

Come spring time the high CYA will have totally fixed itself. It also degrades about 4-5ppm a month so even with a solid cover and no rain added you’ll be down about 30ppm when you open.
 

cowboycasey

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It is safe to swim up to SLAM level as long as you can see the bottom of the pool.. :)
 

PhotoBug

Well-known member
May 25, 2017
117
Erial, NJ
Thank you? So an FC number that high consistently is ok? Also, is there anything else we can do to speed up the process?
 

cowboycasey

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I swam in my pool with friends at CYA of 80 and SLAM FC at 31, they did not even notice it was high.... Once you get the FC holding and the algae is dead you can help it along by adding DE into your sand filter :)

 

PhotoBug

Well-known member
May 25, 2017
117
Erial, NJ
It’s only high if you don’t believe the CYA relationship.

But you understand the CYA buffers the FC so it’s all good.

You should get about 3ft of off season rain / melters snow so you can easily limp along for the rest of this year maintaining a higher (but *not* ‘high’) FC per the FC/CYA Chart

Come spring time the high CYA will have totally fixed itself. It also degrades about 4-5ppm a month so even with a solid cover and no rain added you’ll be down about 30ppm when you open.
Got it!!!!!! I was slamming but got concerned about high FC……I understand now.

I will continue slamming and not worry about PH until my pool passes over night test.
 
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