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.
In short: you'll probably be fine.
To explain, the primary danger is oxygen leaching through the plastic and oxidizing your beer. This is a real risk however you can minimize it. I believe it will take months at the rate of diffusion. Your beer will come out tasting like stale crackers or wet cardboard.
The reason chemicals in the plastic may leech into your beer and not the water is because beer is acidic while water is fairly neutral in pH. A few hours in the sun may drive off those chemicals. There is probably some food-safety regulation governing water jug composition guarding you from harmful chemicals.
Try it out. If you don't have a problem, relax & don't worry.
I often used plastic jugs when first starting out, probably because they were cheaper and available. One thing I recall is the relative difficulty in removing krausen scum from the inside - perhaps the plastic isn't as smooth as glass; I'm not sure. But this was also years ago and I'm not sure I tried as hard as I would now. So perhaps with a good soak in the right chemicals - Oxyclean, bleach, what have you - it would be no problem.
I don't think you can taste bpa, but certainly microwaving food and eating it from bpa plastic will raise bpa levels in your blood stream. However, it appears that ceasing the behavior also drops the levels back down, so I'm not convinced it's a great health risk and unless you put hot wort into the jug, it shouldn't cause this effect.
The other issue with any plastic is the permeability; they simply let more air in than glass. PET seems to be much better than polycarb, but glass is 0. Having said that, I've switched over to plastic Big Mouth Bubblers for my primaries, but more for the convenience and price than anything else.
I use a #7 five gallon jug to transport brewing water from the RO machine in front of the market to my house... but I ferment in glass carboys. I had two batches spoiled by a hairline crack on the bottom of a better bottle. When I moved it, I smelled sour spoiled beer, and when I tasted it, it was awful. I noticed it just after I had brewed a batch, and the local homebrew shop had closed 10 minutes earlier. I put the new batch on top of a platter filled with starsan, but the bugs in the scratch ruined both batches.
I ran out of bottles and threw some of the last beer into a Poland spring bottle with a screw cap. It blew up like a bomb and became highly pressurized. I did it more for an experiment to find a secondary fermentation potential. I added priming sugar and maple syrup to the full batch and for this experiment I added a lot more extra maple syrup, maybe table spoon for about one beers worth, so it explains the high pressure bottle bomb. I degassed it and tasted a drop. It's amazing. I feel as though I need to pour it down the drain. I wonder if it is safe to do a natural carbonation in a plastic bottle like that. Any input would be appreciated. The main batch is all in glass bottles but this plastic test bottle came out incredible.
What about the alcohol in the beer?
It's a solvent so might it leech chemicals from the plastic?
Lots of studies show that #1 and #2 are okay with water but has anyone studied if it is good with alcohol?
Since PH and Alcohol each provide the possibility of leeching, and since cleaning and micro-cracks are an issue with plastic, personally, I will stick to glass.
As one is only fermenting for 14 days in a pre-used plastic container I would argue that it is safe to ferment in a plastic food grade container. In fact one might argue that the more one used it for fermenting the safer it would be as there is only a limited and very small amount of "objectionable" chemicals in the plastic to begin with. I presume the original water was consumed without complaint so one might wonder why any beer brewed in it would be "bad". Yes there may be better things to use but I don't think it would be deleterious per se to use this item.