How do you maintain your FC level (with SWCG)?

BowserB

Silver Supporter
Jul 29, 2018
657
"Old" Katy, TX
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I've had an IC40 only since June 1, and I've yet to find a combination of run time and % that hold FC constant. It seems I get it creeping up at .5-1.0 per day or dropping at a similar rate. My pump runs on IntelliConnect, currently 9:15am to 7:45pm at 1650 RPM and the same speed from 2-4am. The IC40 is on a mechanical timer that I use to have the IC40 only power on and off while the pump is running already, while also striving to have it run when the sun is up.

At present, the IC40 runs from 11am to 5:30pm at 20%. If you look at my logs the last was 4 days ago an 6ppm, and that was my target, but three days earlier it was 7, so I adjusted my schedule to what it is currently. Today FC came up as 5.5ppm, so it seems I'm losing .5ppm every two or three days. This is the most stable it's been, as previously any change results in a rise or fall of 1ppm a day. Yes, I admit I'm trying to micro manage the free chlorine. I'd like to not worry about it dropping, but I'd also prefer to not have it eventually climb to SLAM levels! Frankly, I wish the IC40 had a setting between 20% and 40%, since at 20% FC drops and at 40% in rises. For some reason, my tinkering with run time hasn't yet for certain held it where I want. Today, I'm going to add some 10% liquid chlorine to get back to 6ppm and see if my settings will hold it.

Oh, in case it's relevant, I get my water samples in the morning before the pump is running, which is typically 12 hours or more since the IC40 shut off. Sample is collected from about 3ft down in the 6 foot deep end of the pool.

What do other people do? Any other micro managers out there? I'll save Total Alkalinity for another day. :)
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,845
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'd like to not worry about it dropping, but I'd also prefer to not have it eventually climb to SLAM levels!
It will not. Set it so that your FC does not drop, if the FC rises, the UV or birds or whatever will drop it back. At this time of year however, you will have lessening FC loss pretty rapidly as the sun angle changes.
 

BowserB

Silver Supporter
Jul 29, 2018
657
"Old" Katy, TX
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
It will not. Set it so that your FC does not drop, if the FC rises, the UV or birds or whatever will drop it back. At this time of year however, you will have lessening FC loss pretty rapidly as the sun angle changes.
Good point Marty, about the sun. Most people don't realize that the sun's winter angle is actually lower in the sky than it appears. Diffraction by the atmosphere acts like a lens, so there is a lot more UV lost to the ozone layer than in summer. I learned that from a book called "Fun With Astronomy" given to me in the 4th grade (1955). Our family did not have a swimming pool, but we did get an 8' by 20" wading pool from Sears one year. I had no knowledge of the importance of free chlorine at the time.
 
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