How fast does FC level peak during SLAM?

apv

Active member
Apr 30, 2019
30
Austin, TX
Hi there,

Just started my first (and hopefully only) SLAM process.

Before I started,

FC = ~0
pH = 8.0
CYA = ~40

with target of 16 for FC.

I added muriatic acid to lower pH (about 30 oz), waited a few hours and added 3 gallons of liquid chlorine (@10%). It has been about four hours since I added the liquid chlorine and I just tested,

FC is ~6.0 (using Taylor SpeedStir)
pH is ~7.6.

Question: How long does the liquid chlorine concentration take to dissipate and peak? I am trying to figure out if I need to add more liquid chlorine now (ie we have peaked and are far from our goal of 16) or wait until tomorrow to remeasure FC.

Thanks in advance.
 

justinc

Gold Supporter
Apr 3, 2019
460
Texas
If the pump is running, you can measure again in 30 minutes after adding. Your level is likely less than what you added because some of it was consumed by algae in the water or other organics. What's your combined chlorine?
 
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mknauss

Mod Squad
TFP Expert
May 3, 2014
17,835
Laughlin, NV
During a SLAM, especially at the start, you need to test your FC and add liquid chlorine back to your SLAM level every couple hours. That should slow down after the first day or two.
 
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YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
10,210
Evans, Georgia
If you have organics in the pool, the FC you add via that 10% liquid you added, will start oxydizing the organics almost immediately. The FC will drop as it gets chewed up... which can be quick.

You can re-test your FC an hour later and re-dose as needed to keep you up at SLAM level.

Maddie :flower:
 
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Teald024

TFP Guide
The chlorine is well mixed within 30 minutes after you add it to the pool. It would likely peak in uniform concentration at 15 minutes after you add it and then degrade from there. So at 4 hours after the addition, you should definitely add more chlorine and keep as close to SLAM levels as possible. For the first couple of days, the more you can test and add the better.
 
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apv

Active member
Apr 30, 2019
30
Austin, TX
Thanks everyone.

I added two more gallons of liquid chlorine at around 5pm. It is almost 10pm here in Austin and I just checked.

FC = 10.5

I will add another gallon or so to try to get to FC of 16 (before turning in for the night).

I am doing the Chlorine Drop Test using the SpeedStir --- one thing that is weird, after I have tested for FC, I proceed and try for CC but with the introduction of DPD-reagent #3, the solution doesn't turn back pink. I suppose that means my CC = 0 ---- if so, is that a potential issue?
 

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