How quickly does Chlorine lose its punch?

[dunginhawk]

So I have been fighting FC for the last few weeks and I may have finally figured out why.
Bottles of 12.5% i bought from menards this spring are WOEFULLY underperforming.
For instance, I was at FC1, wanting to get to 12 to SLAM and I put in 5 oz as per pool math, and the immediate test showed up at 4.5ppm.
So that only added 3.5-4ppm. about 1/3 of what it should have.
Does chlorine go badly that quickly?
Just curious
thanks

 

[mknauss]

Breakdown of bleach over time by storage temperature

I found a nice web page that will predict the loss of strength of stored bleach over time based on the storage temperature. Take a look here.

www.troublefreepool.com

Liquid chlorine degrades. See the above thread for specifics. Yours sounds very normal.