Chasing a ghost?


Well-known member
Jun 29, 2009
Vero Beach, FL
I've had my pool FC up at or above FC=25 (CYA=60) all week and still get overnight loss. When it was at 25, the next morning I measured 23.5. Then I brought it to 30 and the next morning it was down to 28. Yesterday I had it at 35 (by accident) and this morning it is 32. Seems like the more I add, the more it drops.

There are no indications of algae and the pool is sparkling clear. I only decided to shock when we got a ton of rain and I suspect fertilizer may have gotten in the pool from the lawn guy, and my FC dropped to 1.

I'm getting a lot of pressure from wife and kids wanting to swim. So I'm thinking of letting it drop to 10 and just leaving it there until November and shocking it again then if I need to.


LifeTime Supporter
Apr 2, 2008
Acton Maine
I suppose if you have dropped in fertilizer the cl would be consuming it as it is technically an organic. But my concern would be that if the organic was unsanitizing the water and you start swimming before you have no fc loss, you may be posing issues to your kids. I'm no expert, but I would keep shocking for a few more days to be safe, it looks like you aren't far from your no fc loss anyway. I'm sure those who are more in the know will weigh in. Good luck.


TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
SWSuburban Chicago, IL
It simply means you'll go thru more chlorine trying to maintain normal levels - cuz something in the water is consuming the chlorine more rapidly than normal. You have to be diligent on your testing and maintaining so that you don't drop below your "min" - that would be when you risk unsanitary conditions.


TFP Expert
LifeTime Supporter
Apr 4, 2009
Lborne...can you post a full set of results?


Curious why you are bringing FC up so high? I understand the overnight FC loss test...but the more FC, the higher FC loss the fact that you lost more FC when you mistakenly raised it to 35ppm...makes some sense

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