PoolSupplyWorld has a retail store in Rocklin, CA. I bought a good amount of 12.5% chlorine from them because they have great prices at $3 per gallon. This is my first pool season, so I am still learning. I couldn't figure out why the Pool Calculator wasn't working well for me and my FC wasn't raising as high as I expected when I added the 12.5%. So I bought some Clorox and added that. To my surprise, the 6% Clorox was raising my FC about the same as the 12.5% from PoolSupplyWorld. Hmmmm...... So I tested the Chlorine content... the Clorox tested at 6.5% and the 12.5% tested at 6%. WOW. The 12.5% is manufactured by Sierra.
I called PoolSupplyWorld and shared my results. They are in the process of changing suppliers, and apparently this is one of the reasons. I was told I would get a call back the next morning with an ETA for Chlorine from their new supplier. This was several days ago, and I am still waiting for that phone call. I was also a little disappointed that they didn't offer any kind of compensation, considering what they sold me was less than 1/2 the strength it was supposed to be.
So, I just wanted to share my experience in case anyone else buys liquid chlorine from PoolSupplyWorld, beware the 12.5% from Sierra!