PH keeps rising during my SLAM?

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
I was over 8.2 in PH prior to my slam, so I added a gallon of MA, and it dropped to 7.2. I loaded 4 gals of CL (13.5 HDX from HD), and I was about 34 CL. Took my readings this am, and got the following:
22 CL
0 CC
400 CH
130 TA
50 CYA
PH 8.2 +
2600 salt

Per pool math, I just added 1/2 gal of MA. I'll bump my CL back up to 34 again as well (there is some mustard in the corners and stairs), but I'm pretty surprised the PH when up so much overnight. Am I missing something? Water looks nice and clear, and but for a little yellowness, the pool looks otherwise good.
 

proavia

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Feb 6, 2015
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Chandler AZ
pH test will read falsely high with CL above 10. If you lowered pH to 7.2 before starting your SLAM, don't bothering test it again until after your SLAM is complete and/or your CL drops below 10.
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
Ah, OK, thanks, I did not know that. So no need to add MA during the slam? I didn't do an OCLT last night, but I've obviously lost CL, so I'll try to test more today, but I"m going to bump it back up to 30 or so first.
 

proavia

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Feb 6, 2015
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No need to add MA during SLAM - as you really have no way of accurately measuring it with CL above 10. No real need to do an OCLT until the water is crystal clear, CC is 0.5 or less and your CL loss between tests gets to a low number (probably <3 CL loss between tests).

You stated CC is 0, but didn't mention water clarity. Do your best to keep CL at SLAM levels by testing . And brush the entire pool surface 1 or 2 times a day as well.

I'm sure you reviewed the SLAM procedure ... Pool School - SLAM - Shock Level And Maintain
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
Thanks, the water is clear, CC is zero, and there is some residual mustard on the steps and corners, I'll try to keep the CL at the recommended 34 and see how quickly I drop. I have a midnight blue quartzscape with abalone, so I'm a bit nervous about "bleaching" out the color by keeping the CL high for extended periods, but I want to get the H20 dialed in and keep it that way ;-)
 

domct203

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Jun 3, 2015
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Thanks, the water is clear, CC is zero, and there is some residual mustard on the steps and corners, I'll try to keep the CL at the recommended 34 and see how quickly I drop. I have a midnight blue quartzscape with abalone, so I'm a bit nervous about "bleaching" out the color by keeping the CL high for extended periods, but I want to get the H20 dialed in and keep it that way ;-)
If there is visible algae, the water is not clear.

I was over 8.2 in PH prior to my slam, so I added a gallon of MA, and it dropped to 7.2. I loaded 4 gals of CL (13.5 HDX from HD), and I was about 34 CL. Took my readings this am, and got the following:
22 CL
0 CC
400 CH
130 TA
50 CYA
PH 8.2 +
2600 salt
If your CYA is 50, your SLAM FC level is 20ppm. Where did you get 34ppm from?
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
OK, thanks. The water itself is clear, there is just yellowing on the steps, but I guess thats attributable to the water, so I'll keep SLAMing til its gone. I got the 34 CL number from the Pool Math chart for mustard algae. I did note the difference with the SWG #'s and normal bleach #'s too. When I re-tested my CYA this morning, it was between 40-50. I realize its a subjective test, but should I try to increase my CYA level during the SLAM, or leave it for now?
 

domct203

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OK, thanks. The water itself is clear, there is just yellowing on the steps, but I guess thats attributable to the water, so I'll keep SLAMing til its gone. I got the 34 CL number from the Pool Math chart for mustard algae. I did note the difference with the SWG #'s and normal bleach #'s too. When I re-tested my CYA this morning, it was between 40-50. I realize its a subjective test, but should I try to increase my CYA level during the SLAM, or leave it for now?
Could you post a link to this chart that shows 34ppm FC for 50ppm CYA with mustard algae? When I put your numbers into pool math, I get a FC of 29ppm for mustard algae, and chem geek's data agrees:
http://www.troublefreepool.com/threads/2177-Chlorine-CYA-Chart

Also, you do not raise the FC to mustard level until after you complete a SLAM, and only for 24 hours. More here:
https://www.troublefreepool.com/content/148-mustard-algae

Standard shock FC level is 40% of CYA, mustard shock FC is 60% of CYA.

Leave your CYA where it is. When we get a CYA result 'between' numbers, always round up, so your 'between 40-50' would be recorded as 50ppm.
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
Thanks. here https://www.troublefreepool.com/calc.html is where it shows 34 CL for mustard algae, but I think thats just the generic info inserted? I know its lower with the SLAM link.
Ok, so after adding the gal. of CL this am, I am at 30. I'll leave it and check tonight and tomorrow to see what I get, unless you think I need to lower it. Water temp is low 60
s and my SWG is not turned on.
 

domct203

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Thanks. here https://www.troublefreepool.com/calc.html is where it shows 34 CL for mustard algae, but I think thats just the generic info inserted? I know its lower with the SLAM link.
Ok, so after adding the gal. of CL this am, I am at 30. I'll leave it and check tonight and tomorrow to see what I get, unless you think I need to lower it. Water temp is low 60
s and my SWG is not turned on.
Pool Math shows mustard shock as 29 with a CYA of 50:

poolmath2.jpg

I would let FC come down a bit & maintain FC at 20-22ppm. Once you finish the SLAM, raise FC to 30ppm for 24 hours only, then let it drift down to target levels.
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
OK, my CL dropped to 22 again (?), and I had just some pink clouding, so 1 drop of reagent gave me .5 CC. 130 TA and holding. Is it usual to see that much of a drop in CL overnight, without a lot of organic matter in the pool? The visible mustard is almost completely gone, and i'll give it another good brushing before work, but in a way I'm relieved my CL came down, as I was concerned it would "bleach out" my midnight quartzscapes. I will likely increase the CYA after the slam to try to maintain my CL better. Thanks for the input,
Joel
 

duraleigh

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Don't worry about bleaching anything. These numbers have been well thought out over a long number of years and they are perfectly safe. Focus on your FC and keep it right until your SLAM is complete
 

jbailey895

Well-known member
Apr 25, 2016
107
Carlsbad, CA
OK, thanks, had 22 FC and 0 CC today, I think I'm outta the woods, no visible mustard anymore either, I'll keep an eye on but expect to let the FC drift down now. . .
 

domct203

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OK, thanks, had 22 FC and 0 CC today, I think I'm outta the woods, no visible mustard anymore either, I'll keep an eye on but expect to let the FC drift down now. . .
Have you passed the OCLT?