Bad practices or not?

[nasmeyer]

I have a couple of questions about possible contamination points during fermentation. I use plastic fermentation buckets placed in a large tub of water which I either heat or cool based on time of year, and can keep my fermentation within one degree of whatever set-point I shoot for. A possible drawback is that some batches I have done this way have similar off-flavors to others I have done the same way. I was wondering if it is possible over a four week fermentation that I could be drawing unsanitary water or organisms through the plastic from my heating water to my beer? I have read in the past that O2 can filter through plastics this way.
I also ferment some of my batches in my 90 year old basement and know that during fermentation the Co2 will off gas through the airlock and create pressure which wouldn’t allow any unwanted gasses to enter the bucket, but after the off-gassing stage, is it possible I am getting unwanted gasses, odor, or O2 into my bucket through the plastic? Since the basement can have a slight mildew odor I was wondering if that could transfer through plastic too.
Are my concerns valid or not possible at all?

 

[TrainSafe]

I have a couple of questions about possible contamination points during fermentation. I use plastic fermentation buckets placed in a large tub of water which I either heat or cool based on time of year, and can keep my fermentation within one degree of whatever set-point I shoot for. A possible drawback is that some batches I have done this way have similar off-flavors to others I have done the same way. I was wondering if it is possible over a four week fermentation that I could be drawing unsanitary water or organisms through the plastic from my heating water to my beer? I have read in the past that O2 can filter through plastics this way.

Nope. While it may be possible for a minute amount of gas to pass through the plastic over a very extended time (months and months, or years) you aren't going to get off flavors from your plastic fermenter or the water bath.

There is no way that any organisms can move through the plastic into the beer.

A more likely cause would be your water that you are using for brewing. The mineral content may be contributing to your flavor issues. What types of flavors are you detecting? What is the quality of your water? Do you filter?

I also ferment some of my batches in my 90 year old basement and know that during fermentation the Co2 will off gas through the airlock and create pressure which wouldn’t allow any unwanted gasses to enter the bucket, but after the off-gassing stage, is it possible I am getting unwanted gasses, odor, or O2 into my bucket through the plastic? Since the basement can have a slight mildew odor I was wondering if that could transfer through plastic too.
Are my concerns valid or not possible at all?

While this is theoretically possible, it would require a vacuum to be created in the fermentation vessel. The CO2 moves out through the airlock because the pressure on the inside is greater than the environmental pressure. I suppose if you pressurized your house, then you could force O2 into the fermenter via the airlock. If you have a 90 year old house I'm going to wager that it is nearly impossible to pressurize it sufficiently to induce oxygen into your beer.