Overnight FC Loss Test

sb127

LifeTime Supporter
Jul 16, 2010
32
Dallas, TX
This might be a dumb question, but if my CC is measuring zero and pool water is sparkly clear...is there any reason I should do an overnight FC loss test? I assume there could be organics in my pool that the FC is wiping out as fast as it enters the pool and thus not building up CC. Or is that not a realistic thought?
 

duraleigh

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TFP Expert
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In The Industry
Apr 1, 2007
31,713
Sebring, Florida
It's a good question. We often use these criteria to describe a pool thats in really good condition....

1. Your pool water is sparkling
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

So, you've met two of the three and, theoretically, you need to meet the other one to eliminate the possibility you stated above.

You could ALMOST do the same thing by calculating your daily chlorine loss. Anything around 1.5 to maybe 3ppm loss would indicate that there are no organics. The overnight FC loss test, however, is the test that absolutely nails it down and leaves no doubt.
 

JasonLion

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May 7, 2007
37,880
Silver Spring, MD
If everything is going well, there isn't normally any reason to do an overnight FC loss test. It is normally only done when you think there might be something wrong, or you are shocking the pool.
 

sb127

LifeTime Supporter
Jul 16, 2010
32
Dallas, TX
Thanks for the advice. That's about what I figured. I may do it tonight just out of sheer curiosity. That and I'm a little test kit happy anyway. :mrgreen:

I'm just getting started, so I'm trying to get a handle on what the daily FC loss is anyway. Based on one day it appears to be 3 ppm. After another few days, I'll have a more solid idea. 3ppm doesn't seem too out of line especially since the pool gets about 8 hours of full Texas sun.
 

sb127

LifeTime Supporter
Jul 16, 2010
32
Dallas, TX
Bumped my FC up to 6.5 (CYA 50ish) yesterday evening and it held overnight....measured 6.5 FC again this AM. Thanks once again for the info guys. :goodjob:
 

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