Stocking up on pool shock for water purification

I'd been wondering how to store bleach long-term since it breaks down in just a couple years, and then I found some threads on Survivalblog about storing pool shock for water purification.
http://www.survivalblog.com/cgi-bin/mt4 ... 2&limit=20
It hadn't crossed my mind (I don't have a pool)
but tonight I just bought my first 15 pounds of pool shock from Wally World. Any of the rest of you stocking up on it? Now might be a good time before the summer ends and pool shock might not be as readily available.
http://www.survivalblog.com/cgi-bin/mt4 ... 2&limit=20
It hadn't crossed my mind (I don't have a pool)
