FC demand

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rjb1211

Well-known member
Jul 29, 2017
216
Harrisburg,PA
Pool Size
37000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I found the SWG Run Time Calculator. One of the input fields is FC demand.

I know that is a moving target and has too many variables to predict but I need to start someplace. Can someone give me an idea of what to enter as an approximation for this time of year in Pennsylvania while I get it figured out based on my pool?
 
My pool, with a solar cover, heated, CYA around 70, in mid-Michigan (so not that much different climate-wise to you) is running almost exactly 2ppm right now.

If I set my SWG on 10% @ 24hours (1.5ppm/day), I notice a very slow decline in measured FC.
If I set my SWG on 15% @ 24hours (2.3ppm/day), I notice a very slow increase in measured FC.

Unfortunately, I don't have a 17.5% setting... :cool:
 
rjb,

It does not matter what number you pick because it will be wrong anyway... :mrgreen:

I'm with Gene, 2 ppm sounds about right to me..

Keep in mind the whole idea is to try and stay at your Target range or slightly higher.. You never want to try and stay between your minimum and your Target.. Unless of course you just want to get algae... :oops:

Thanks,

Jim R.
 
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Based on your suggestions I started with 2ppm and after monitoring I found that I was dialed in with my IC40 set at 37% which would indicate FC demand of 1.7. My CYA is currently 50 and I have been getting a FC reading at the end of the day of 7. I do intend to bump up the CYA some.

This has been for April with water temps in the mid 60's and daytime air temps mostly from 55 to 75, although the last few days have been much warmer. FC readings haven't changed with the higher temps. It is spring so there have been cloudy and rainy days.

What should I expect as we get into summer weather? Have I got it right that more intense sun is going to increase the FC demand? If so by how much?

BTW - when choosing equipment I was a little concerned that the IC40 wouldn't be up to the task but it appears that was unfounded.
 
rjb,

An IC40 in a pool in Texas or Arizona, would not work well in the middle of the summer..

Even in PA, your FC demand will increase as we move into the summer..

Kind of the whole point in testing is so you can adjust your FC up or down based on the amount of sun the pool is getting.

In my case, I adjust up about once or twice a month, as we get closer to summer, and then down as we move into winter.

As time goes on, you get a sense as to what is happening and can test less.

Thanks,

Jim R.
 
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