Overnight FC Test is close, should I shock?


Active member
Jun 7, 2010
Huntsville, AL
Finally, I have a night where I actually took the sample about 10:15 PM, and was up at 5 AM and got the next sample.

My measurements last night using the TF-100
FC - 3.5 - 4.0 (just a touch of pink before going clear on the 8th drop)
CC - 0
pH - 7.6
TA - 80
CH - 220
CYA - 85

FC 2.5-3.0 - again much closer to 2.5
CC - 0

It has been hovering around 100 degrees for the last week here in Huntsville, AL, no cloud cover or shade for the pool at all, and it was still pretty hot when I was out at 5 AM. Pool School says 1 is about the threshold, but I am wondering if the high temps are having an impact and may have me loosing more Cl than might be normal. Should I shock? The water looks good, but have never been convinced I have been keeping enough CL in there. I know I should at least get it to around 6 by adding bleach, but wanted to see how my new generator was holding it.

Thanks for any help/suggestions.


LifeTime Supporter
Apr 27, 2010
Fleming Island, FL
I would say with your water looking good and no CCs that you should be fine. However, your FC level is running low for your CYA level of 85. You should be keeping the FC above 4 ppm at the minimum. You need to bump up the percentage or time on your SWG to keep you above 4 ppm FC at all times.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
If it's been that hot, I'm guessing the pool's been getting a lot of use. Lots of sweaty bodies cooling off. That could sap your FC.

Try running FC a bit higher and check overnight loss again in a few days. If it's clean and clear I doubt there's anything to worry about.