Corny Keg Sizes and Parts

Sizes

Dimensions, and the number that actually matters

The number that matters for a kegerator is not in that table. Fit posts and push ball lock disconnects onto them and a 5 gallon keg’s overall height reaches roughly 27 inches. That is the figure to check against a cabinet’s internal height. Low-profile or right-angle disconnects buy back an inch, which is sometimes the difference between fitting and not.

The 2.5 and 3 gallon sizes are genuinely useful for small batches, for splitting a batch across two yeasts, and for fitting a spare into a full kegerator. Pressure ratings are comparable across sizes.

Posts

Ball lock and pin lock

Two incompatible standards, inherited from the soft drink industry these kegs came from.

Ball lock

• Disconnects push on and lock with a sliding collar.
• Gas and liquid posts are different sizes so you cannot cross them -- gas posts take a 13/16 in socket, liquid posts 11/16 in on most kegs.
• The homebrew default. Nearly every kit sold is ball lock.

Pin lock

• Disconnects twist onto pins.
• Gas posts have two pins, liquid posts three.
• Kegs are slightly shorter and wider than ball lock equivalents, which occasionally helps with cabinet height.
• Turn up cheaply secondhand and are perfectly good -- they simply need pin lock disconnects.

Pick one standard and stay with it. Mixing means two sets of disconnects and a recurring source of confusion in a cold cabinet.

Lids and PRVs

Three variants worth knowing

• Pull-ring PRV. A pressure relief valve you can lift to vent the keg manually. The most useful variant: venting is needed for releasing excess carbonation, purging, and opening a pressurized keg safely.
• Fixed PRV. Relieves automatically at its set point but cannot be operated by hand. Workable; you vent through a gas disconnect instead.
• No PRV. Older lids. Replaceable, and worth replacing -- a keg with no relief path is a keg you cannot vent.

Lids are interchangeable within a keg family, so upgrading an old lid to a pull-ring PRV version is a cheap improvement.

Dip tubes

Three options and when each matters

• Standard liquid dip tube. Reaches almost to the bottom of the keg, so it draws every last drop -- and also all the sediment that settles there.
• Shortened dip tube. Cut down so it sits above the sediment line. Gives clearer early pours and permanently leaves beer behind at the end.
• Floating dip tube. A short tube with a float, so the pickup sits just below the beer surface regardless of level and always draws the clearest beer available. Close to mandatory if you ferment in the keg, and a genuine improvement for serving too.
• Gas dip tube. Very short -- it only needs to reach the headspace. If a keg pours nothing but gas, check that the gas and liquid tubes have not been swapped.

Seals

The complete set, and when to replace it

Five pieces of rubber, and all five are consumables:

1. Lid gasket -- the large O-ring around the oval lid.
2. Gas post O-ring -- under the post, sealing it to the keg.
3. Liquid post O-ring -- same, on the other post.
4. Gas dip tube O-ring -- inside the post, sealing the tube.
5. Liquid dip tube O-ring -- same, on the liquid side.

Replace the whole set on any used keg before first use, and replace individual pieces whenever a leak test shows bubbles. A complete seal kit is inexpensive and it is the single highest-value thing you can do to a secondhand keg.

Leak testing procedure is in homebrew kegging setup; why homebrewers use these rather than commercial kegs is in corny keg vs commercial keg.