I’m hoping to do a secondary fermentation for two batches that are currently fermenting in carboys and am curious if I can siphon the beer into a bottling bucket, clean and sanitize each respective carboy, and then transfer the beer back into that same carboy it’s currently fermenting in? My concerns are:
Contamination from the potential of germs around the bottling bucket nozzle
Contamination from increased exposure to air by transferring the beer twice
Contamination from exposure to 1.5 gallons of empty space at the top of the carboy (though that won’t really be much different than just leaving it in the carboy it’s currently sitting in).
Contamination is not the biggest risk. You will be heavily oxidizing your beer. There is no benefit to racking the beer for what old homebrew books called “secondary fermentation.” Just leave it in the carboy until it is ready to bottle. The “empty space” in the carboy is currently filled with CO2.
You didn’t mention anything about the beer that seems to necessitate racking the beer to secondary. If you don’t need to rack it unnecessarily then you shouldn’t to avoid needless oxidation opportunities. As Robert points out, contamination is far less of a risk than oxidation.
This seems to be the common theme I’m hearing about the old tradition of transferring to secondary after initial fermentation. The fears were oxidation if beer left in a plastic bucket more than 3 weeks or so, and that too much time in contact with the trub can lead to off-flavors. Now it seems like everyone leaves in glass or stainless from primary to packaging with no perceivable change to the beer from the trub.
I think my beer got better when I started skipping the secondary. I use plastic, glass, and SS with no real noticeable difference other than the damn sexiness of the SS. At this point I do a purged transfer from fermenter to keg. I have had oxidation problems and they are noticeable and disappointing.