My Rubber Stopper Won’t Stay In My Glass Carboy

Rubber Stopper With Air-LockDear Adventures in Homebrewing,
I hope you can help me out. I am having a problem with my 5 gallon glass carboy fermenter. I started a wine from raspberries a few days ago in my bucket fermenter. Now its time to put the wine in the carboy but the rubber stopper will not stay in the opening. It keeps coming out/coming loose. I ordered the size your company suggest. Any ideas?
Seth A.
Dear Seth,
This issue can arise if there is moisture on either the stopper or your 5 gallon glass carboy. Both the side wall of the stopper and the inside of the carboy’s opening is very smooth. This smoothness is what allows the stopper to seal the carboy air-tight, but just a little bit of moisture can cause slippage, allowing the stopper to back out of the opening. This is what you are experiencing.
My suggestion is to get a paper towel and dry the stopper off completely. Then dry the inside of the carboy’s opening. Once you eliminate the moisture in these two areas, you should be able to obtain a permanent, snug fit.
If this does not solve you problem, you can try going to the next size smaller stopper, but this should not be necessary. You can also use a wire to strap down the rubber stopper. Just wrap the wire around the neck of the carboy then across the top of the stopper. Bailing wire seems to work the best for this.
I hope this helps you out.
Best Wishes,
Customer Service at E. C. Kraus
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

3 thoughts on “My Rubber Stopper Won’t Stay In My Glass Carboy

  1. Thank you so much, I was having the same issue.. even after wiping the bung and inside with a paper towel (which I was a little leary of doing as I am sure some paper towel dust gets in the fermenter). I was looking for some sort of ‘carboy stopper clamp’ to keep it in place, but the wire is a good idea!

  2. For anyone out there that is still experiencing the bung slipping loose. Try this.. Find a plastic cap that will sit loosely on the top of the bung (I use caps from fruit juice bottles) Drill a hole through the top to accommodate an airlock. Around the side of the cap drill three evenly spaced holes. insert a small zip tie through each hole and fasten each one so that the loops will reach down to just below the ridge of the bottle neck. Then all you need to do is wrap another zip tie through each loop below the ridge and adjust your ties to pull the bung down snugly. when ready to open your bottles just cut the zip tie around the neck leaving your 3 loops intact for the next time. Another alternative for the horizontal zip tie around the neck is a strong piece of string or wire tie.. Cheers,

  3. Mine was having the same issue and I was concerned about contamination if I were to dry it off. I used plastic wrap to seal tightly around the cork. It seems to be holding the cork in place and keeping any potential air out!

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