How quickly does Chlorine lose its punch?

dunginhawk

Bronze Supporter
Jul 10, 2018
471
CLIVE/IA
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