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Big Mouth™ Modular Keg 5 Gallon


SKU# 42500

The first-ever expandable keg!

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Introducing the first keg purpose-designed for homebrewers. The Big Mouth™ keg packs the power of a draft system—and then some—into a revolutionary serving system. A 5 gallon keg that can be completely broken down for deep cleaning. If you need a portable solution, take out the Expansion sleeve for a compact and portable 1 gallon keg. Slide it in your fridge. Pop it in a cooler. Share, anywhere.

  • 5-Gallon size
  • Withstands up to 40 psi of internal pressure
  • Completely breaks down for easy cleaning
  • Collapses into a portable 1 gallon size when needed
  • Crafted from heavy duty 304 Stainless Steel to last a lifetime

Modular Keg Instructions

Modular Keg Expansion Kit Instructions

Also available in a 1 Gallon size!

Availability: In stock

Big Mouth™ Modular Keg and Expansion Pack Kit

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  • Big Mouth™ Modular Keg and Expansion Pack Kit
  • Big Mouth™ Modular Keg and Expansion Pack Kit
  • Big Mouth™ Modular Keg and Expansion Pack Kit - Mini Keg
  • Big Mouth™ Modular Keg and Expansion Pack Kit - Mini Keg
  • Big Mouth™ Modular Keg and Expansion Pack Kit - Expansion Piece
Product Details
When the party is over, Big Mouth™ completely disassembles to fit in a dishwasher. Effortlessly clean every nook and cranny.

Modularity means more than just a cleaner, more sanitary keg. It’s versatile; offering both 5 gallon and 1 gallon sizes in one keg. Start with the 5 gallon keg when you’re kegging on normal brew days, or collapse back to 1 gallon for keeping it in your fridge or party-ready portability.

Equipped with a revolutionary access port for easy flavor additions. Hang a hop bag or oak spiral from the included hook to customize any batch. Plus, the smaller port means easier sealing and less chance of oxidation.

Collapse it. Clean it. Customize it. The Big Mouth™ Modular Keg is designed for sharing premium homebrew at its prime, from the first batch to the five-hundredth.

Kit Includes:

  • Modular Keg - Keg Top & Base
  • 2 V-Band Clamps
  • 2 Silicone Center Gaskets
  • 5-gallon Expansion sleeve
  • 2 Dip Tubes: Long for 5 Gallon, Short for 1 Gallon

Needed, but not included, is a CO2 cylinderRegulator, and Ball Lock Gas (KX03) and Beverage (KX05) lines.

We recommend a 7/16" wrench or deep socket for tightening the V-Band Clamp.


Full 5 Gallon Keg with Extension: W: 11" with V-band; H: 26"
1 Gallon Mini-Keg Only: W: 11" with V-band; H:11"
Extension Only: W: 11" with V-band; H:15"

Also available in a 1 Gallon size!.
Additional Information
3.6 / 5.0
9 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Great idea, poor execution
The overall quality of construction seemed good except for the V-band clamps. Despite following the directions supplied with the kegs I could never get the kegs to seal properly without stripping, and thus irreparably damaging, the V-band clamps. I actually had NB send me a couple of replacement V-band clamps which also became stripped after the first use. I eventually abandoned the modular kegs and fell back on my old ball lock corny kegs for my kegging needs.

NB customer service was excellent, as always, but this product had some serious issues.
January 2, 2018
1 year ago
Great keg.
Great for experiment batches or 5 gal. Works like a charm.
March 1, 2017
over 2 years ago
I hated this system. NB customer service was great and tried to help me to get it to work, but I had to send back multiple sets of this product because it would simply not seal and hold CO2. I eventually went with cannonball kegs, which are working out great.
January 22, 2017
over 2 years ago
Modular Keg
Very good quality. Excellent versatility and easy to change from 5 gallon to 1 gallon.
June 23, 2016
I may have just gotten a bad run of bands but I've had two where one of the nuts on each galls up about 1/3 down and cannot be removed. Received a new one from Northern Brewer and their great customer service, but am worried it will just happen again. Plan to just stick to regular kegs to avoid the hassle.
June 9, 2016
Keg lube
Lube should be added to every keg order. Assembly and cleaning are a snap
June 6, 2016
Great product and very easy to clean. The overall fit and finish is very nice. I am very happy with my purchase.
March 3, 2016
New idea for ways to bring our beer to get togethers
It is slightly awkward to set up. Recommend getting deep sockets that match the side clamp and the dip tubes to help make a tight fit. Once you are good and sealed, it is an awesome way to share homebrew away from home base with that quality draft experience.
December 23, 2015
Beautifully made
I'm amazed at the craftsmanship on the Big Mouth Modular Keg . The fit and finish is second to none. You will not be disappointed
December 19, 2015
Start typing your question and we'll check if it was already asked and answered. Learn More
Browse 29 questions Browse 29 questions and 39 answers
I have a True kegerator installed undercounter in my kitchen that only has 26.25" of interior clearance. I'm wondering if this keg in the 5 gallon format will fit along with the necessary couplers. As it stands currently, when I use a standard Sankey 1/6 keg I need to use the low profile perlick coupler. Anyone know if this would work for me?
A shopper on Dec 22, 2017
BEST ANSWER: My name is Donny been home brewing since grad school in 1995, I have this big mouth modular keg 5 gal and it will fit in that kegerator, I have 4 of these keg fridges it fit fine with the couplers on it! GOOD Choice good luck!
Cheers DOC
Can you convert from 5 gal to 1 gal with the same batch. For example, I brew a 5 gal batch and keg it in the modular keg and then want to take 1 gal to a party, can I keep the rest of the 4 gal in the keg and take off with the desired 1 gal top?
D A on Dec 28, 2015
BEST ANSWER: No. The top and bottom of the keg are the same, in other words there's only one top and bottom. It's just the middle that you can extend to make a taller 5 gallon keg.
What size wrench do you need for the v band
E L on Aug 2, 2016
BEST ANSWER: A 7/16" socket will do the job!
Does it come with two different size dip tubes, one for 1 gal and one for 5 gal?
R A on Feb 18, 2016
BEST ANSWER: Yes, it comes with both.
I'm new to kegging since my wife got me a kegerator for Christmas. I have a question on connecting the gas and beer lines to this keg. My kegerator has a sankey d coupler. Do I need a ball lock conversion or something else? Thanks.
M O on Feb 15, 2016
BEST ANSWER: That keg has ball lock posts on it, so the only way to connect the keg is to use ball lock disconnects. Here are items to swap out on the tubing to hook up the keg:
SKU# K013 Ball Lock Disconnect- 1/4" Barb Liquid
SKU# K012 Ball Lock Disconnect- 1/4" Barb Gas

There is also an option to go with 1/4" MFL threaded disconnects, then you use barbed swivel nut to attach the tubing. The benefit there is that you can put the barbed swivel nuts on the tubing, and get adapaters to make it easier to switch back and forth between sanke and ball lock couplers.
Can i buy this and the expansion kit, and make a 10 gallon corney? I tire of always splitting my 10 gal batches. Thanks
M E on Feb 9, 2016

Thank you for choosing Northern Brewer! Though it might be theoretically possible, I am not sure that I would recommend it. That would be a pretty tall keg for one (basically two corny kegs tall), and like most things that deal with pressure, the more seal points you have, the more likely that you can have a leak. This is not something that we have tested, so we cannot tell you to do it or not to do it, but it would be physically possible! I hope that this helps, let me know if you have any further questions!
Any chance of offering other expansion sizes such as a center piece to make a 2 or 3 gallon batch?
V I on Jan 22, 2016
BEST ANSWER: I just bought this and waiting to use the modular keg w/ the five gallon expansion kit. That would be a good idea for other sizes available. Maybe even four gallon so you could fill a couple growlers.
What type of stainless steel is used for the cylinder?
Richard B. on Dec 24, 2015
BEST ANSWER: Documentation doesn't specify SS type for expansion sleeve. Keg is food grade 304SS. Based on visual/weight/machining comparison, it appears expansion sleeve is same material.
Bought this keg and filled with water for a test. Worked fine, but when I tried to open it back up 3 of the 4 nuts only loosened a few turns then froze on the threads. I had to shear the studs to get it open. Can I buy new clamps or threaded studs?
D O on May 7, 2016
BEST ANSWER: We do have the clamps for these kegs, if needed. If under warranty ( very likely ) we could replace those for you. Contact us with the purchase info and we'll see what can be done to get you fixed up! Your name and email don't bring up an account, so let us know the name on the order, or order number, and we can look it up. -Mike W, Northern Brewer
Where are these kegs manufactured.
G O on Nov 27, 2015
BEST ANSWER: This is manufactured in China
Does it come with two different dip tubes? Or is there something new inside?
Jerry U. on Nov 23, 2015
BEST ANSWER: Hello Jerry

There are two different dip tubes for the 1 and 5 gallon sizes.
Will there be other expansion sizes available? 5 gallon isn't much different than a standard keg (other than the hop port), and 1 gallon is just too small for my purposes. 2.5 or 3 gallon expansions would make this great.
Wendell R on Nov 19, 2015
BEST ANSWER: Thanks for the request! I'll happily pass that along as I would like to see that as well! Cheers! James J.
can you double stack the 5 gal. kits to create a 10 gal. keg?
D A on Nov 18, 2015

It is in theory possible. It isn't however super practical. You'd need to manufacture you're own dip tube

since we do not sell one long enough to get to the bottom of a 10 gallon expanded keg.
So I see 2 ball lock posts, a vent, and some kind of knob thing? What is it?
J W on Nov 18, 2015
BEST ANSWER: That is the lid for the fill port
So the expansion pack also includes the longer dip tube?Also, what has been your experience with the kegs ability to completely seal since you now have a greater number of possible sites for leakage. Beer leakage would be pretty easy to see , but what about the C02?
S K on Nov 16, 2015
BEST ANSWER: The trick there is tightening the V band clamp down correctly. This is all explained in the instructions. When not too tight or too loose

the gasket forms a perfect seal. A iquid or CO2 leak would be evident. I would pressure test before filling. Then the keg will not hold one set pressure you are shooting for and any liquid at the seals would bubble and hiss. This can be how you purge oxygen out of the keg before filling so works nicely in the normal use of the keg. I hope this helps explain! Cheers! James J.
What pressure is this keg rated for? Can you go up to 30psi for force carbing?
Tim D on Nov 16, 2015
BEST ANSWER: This keg is rated for up to 40 PSI. You can force carbonate at 30 PSI with it.
What are the dimensions of the keg (height and diameter) when fully assembled with the expansion pack?
A L on Nov 15, 2015
BEST ANSWER: H: 26" and D: 10"
I love the idea...always wondered if one could be produced!

What is the total volume of the expansion pack?

Can you ferment using it in the expansion mode?

love to see it in a 5.5 to 6 gallon.
S H on Nov 15, 2015

Thank you for choosing Northern Brewer! The total volume is 5 gallons with the expansion sleeve installed. I would assume that you could ferment in it

nothing tells me that you can

and nothing tells me that you can't. But looking at the access port... I don't see why one couldn't fit a drilled stopper and an airlock in there and ferment away!
Any plans for a 3-gallon "expansion"
Kent Erickson on Nov 14, 2015
BEST ANSWER: Not yet. Thanks for the suggestion. I have passed that along as it would not be hard at all to make it an option. Cheers! James J.
Could you use the 1 gal and 5 gal extension together to keg 6 gal.? ...or an extra 1 gal. extension to keg 2 gal?
T O on Nov 14, 2015

the keg itself without the extension holds a gallon

but the extension adds 4 gallons to make it 5 total.

Hope that helps! Let me know if it doesn't.
How often do the silicon gaskets need to be replaced?
S E on Nov 14, 2015
BEST ANSWER: The silicone gaskets are expected to last a very long time. The only need for replacement would be due to tears or cuts.
I love the idea of being able to get in side and clean, or to run through the dishwasher, but what is the size of the footprint. Space is tight when I have three 5 gallon containers on the floor of my keezer. Three of the carney kegs fit, but three of the sixthels from my favorite brewery wont. I'm wondering if I can fit three of these. I don't think that the straps and clamps will be an issue, because I can just face them away from each other. Thanks!
Kyle P on Nov 14, 2015

The keg has a diameter of 10" at the v ring and 9" at the top/bottom. The keg is 10.5" tall without the expansion

and 25.5" with the expansion sleeve installed. Have a wonderful day!
What are the dimensions for this keg?
R Z on Nov 14, 2015
BEST ANSWER: Height 26" and Diameter 10"
What are the dimensions?
D E on Nov 14, 2015
BEST ANSWER: Height 26" and Diameter 10"
What is the dip tube made of and how does it work?
D A on Nov 14, 2015

The dip tube is made of stainless and there is a different length dip tube for the 1 gallon keg

and a longer one for when you put in the modular sleeve. I hope this helps!
What are the dimensions of this keg?
T O on Nov 13, 2015
BEST ANSWER: aporx. 9" diameter

and either 12" or 25" tall
What's the max pressure this is rated for?
B R on Nov 13, 2015
BEST ANSWER: The max pressure is 60 psi.
What are the overall dimensions of the completed 5 gallon keg? Tall and Diameter at widest point?
Wayne M on Nov 13, 2015
BEST ANSWER: The 5 gallon keg is 9 3/4" at its widest. It is 26" tall and that is how much clearance it needs.
What does this include? The keg top. keg base, expansion, 2 V-band clamps, 2 silicon center gaskets, and dip tube? Do I have to purchase anything else to start kegging my beer?
T O on Nov 13, 2015
BEST ANSWER: That is what this product includes. To start kegging you would also need a CO2 regulator

CO2 tank

gas hookups from the keg to the regulator

and serving faucet with tubing and liquid disconnect.

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