measuring shock level


Jul 15, 2009
I want to shock my pool because, yesterday, the TC was at zero after a huge storm and two days away from home. I added chlorine (bleach) last evening, and this morning here are my quick numbers:

FC 3.0
CC 0
TC 3.0
pH 7.4
TA 70
CH 300
CYA 50

Tha chlorine/CYA chart gives me a shock FC between 16 and 20.
The Pool Calculator tells me how much bleach to add to reach FC 16 to 20.

So, I pour that much bleach in, all at once? And then when do I measure FC again? And how do I measure up to 20?

And, do you think I need to shock?

Thanks for your help.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
The FAS/DPD Chlorine test is the only test that will measure high levels of FC....up to 50+

What type test do you have?


Jul 15, 2009
I have the TF-100. So, how do I know I've gotten the FC to shock level? Just by the amount of bleach I add?


Platinum Supporter
LifeTime Supporter
Apr 14, 2010
Stephens City, VA
You add the bleach to get to the target amount. If your gallons, etc are correct, what the calc tells you should get you there. But, if you have organics some of that will get consumed right away soooo....
Add to the target shock.
Wait 30-60 minutes for it to circulate and retest.
Enter that number as now, your target number in the target column, and calculate.
Add that amount.
Wait another 30-60, retest, add if necessary.


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