It is more cost effective to go that route....IF it's actually 12% or more in strength. Depending on storage conditions and turnover rate, the 12% may or may not degrade. I'll have to find the link for it, but around here somewhere Carl (or maybe Waterbear?) concocted a way to test the percentage of chlorine actually in the jug. Let me search around some and see if I can find it, and will add it here.

Edit: Here it is... http://www.poolforum.com/pf2/archive...p/t-10167.html