I’m using a blow off tube for my primary fermenter (glass carboy). I checked it Saurday, the 2nd day of fermentation and water is backing up the tube from the 1 gallon jug I’m using. Water did not enter the carboy, but I did remove the tube from the carboy stopper to allow the water to return to the jug. Am I at risk for contamination? Also, it does not seem to be producing any bubbles into the jug, any advice would be appreciated.
A change in temperature will create negative pressure. You shouldn’t have a problem with contamination.
In the future, leave it be as long as there is plenty of hose between the fermenter and blowoff bucket. One the pressure evens out; replace the hose with a sanitized airlock.