I asked this on Twitter a while back, but I thought I might get some other thoughts on it. I have one of those 5g Poland Spring water jugs. If I get a bung that fits it, is there any reason I couldn't use it as a fermenter (either primary or secondary?). Some people have said it should be fine, others have said that "chemicals in the plastic" will leech into my beer and produce off-flavors. I find this latter argument difficult to accept given that those same chemicals don't leech into the water that the jugs held. Thoughts one way or the other?
The consensus answer is that the only thing safe to put food with non-neutral PH into is #1 Polyethylene terephthalate or #2 High-density polyethylene. The big blue jugs you get with water in them are made from #7 polycarbonate. Polycarbonate has some potential health issues as it can leach, even in water at room temperature, a substance known as Bisphenol A which can have detrimental health effects. There is a movement going on to discontinue use of #7 polycarbonate plastics in the bottled water industry and replace them with #1 or #2. It is my understanding that the company that makes Better Bottles is benefiting from this. I know people will argue up and down that they haven't seen any health effects, but I simply wouldn't bother risking it. Better bottles and bucket fermenters are cheap.
I have fermented in plastic carboys can I cannot recommend it. You CAN get them clean with Oxy-Clean, but they are a PITA. Glass fermenters where you can use a carboy brush or plastic bucket fermenters are superior, in my opinion.
As to the oxygen permeability issue, unless you are going to leave the product in the plastic for years, it should be a negligible effect. #1 or #2 plastics have a very low oxygen permeability.Tweet