Blow off tubing diameter
 

Just a quick question. Been looking around trying to figure the standard diameter of a carboy bung so I know what OD blow off tubing I need to get. I'm assuming 3/8" but we all know what happens when we assume.

yes - and do you just stick it in there or do you seal it somehow?

What kind of bung are you using? The solid rubber ones you can fit a 3/8ths tube into, and yes, just make sure everythings wet with sanitizer and stick it right in there. I'll leave any teenage innuendo out this ;-)

If you have one of the universal ones like this:
http://www.homebrewing.org/Universal-Carboy-Bung-Drilled_p_1387.html

get a 1/2" tube and slide it over the nipple in the middle.

Same deal, just push it on there. Both hoses will seal. There won't be a ton of pressure in your fermenter unless the blowoff tube gets clogged, which CAN happen in a solid bung and 3/8" tube in my experience, but the 1/2" tube on the universal bung has never steered me wrong.

Lastly, if you have a hood, you can use either size, just stick it on the nipple of the appropriate diameter.

I use 1" inside diameter tubing for my carboys

And just shove it into the neck right? This only works for glass carboys. I don't know what OP is using, but this is a good reminder to qualify that my advice above applies to better bottles/plastic carboys.

Yes I use this for my glass carboys. You never have to worry about overloading the tube. I have seen some serious flow coming out of the tube in vigorous top-fermenting yeast. Not sure how a tiny tube would handle that, probably OK for most beers though.

I have a BetterBeer carboy. Plastic, obviously. Still learning my kit. Just got it in the mail today.

I measured my carboy . Looks like a 1.25" OD tube would fit for a fat blow off tube.

I use a 6.5 gal carboy and a 1" diameter blow off tube for the first week. It hasn't been necessary till my last batch-a hefeweizen-it went all the way through the tube to the other end dipped in star san.

If you use a better bottle and want to go big with the blow-off tube.

http://www.homebrewit.com/aisle/p/BB24