Looks like a plastic cooler mash tun in your picture. Are you not worried about that leeching? 
how are you airlocking these vessels? do they have textured or smooth sides? I assume they are food grade if they are made for holding drinking water. I am intrigued by this idea. How is the cleaning? do you feel you can get them clean even in the square corners? do they hold up to hot PBW?[/quote]
I usually just use foil over it. But I also made some adapter pieces so I can use an airlock if desired. Basically, the bottle has a cap with a screwed-in spout. I unscrewed the spout and installed a plumbing piece from Home Depot. I then just stick a stopper and airlock into the plumbing piece. Sorry, no pictures handy.
Yes they are food grade. Mine are#1 PETE, but I’ve also used #2 food grade plastic as well. The insides are smooth and I’ve had no problem soaking or cleaning them. No harder to clean than BB.
Here is an example of one of the containers I use:
http://www.amazon.com/Reliance-Products-Aqua-Tainer-Gallon-Container/dp/B001QC31G6/ref=sr_1_1?s=sporting-goods&ie=UTF8&qid=1349284078&sr=1-1&keywords=reliance+water+containers+7
. I’ve got a couple different shapes and sizes.
