Which Keg Fittings Do You Need?
Most keg fittings jobs fall into one of a few categories: building a new system and needing the right keg connections, replacing a worn or leaking component, or adding something that makes the setup work better. Here’s where to look depending on what you’re after.
Ball Lock Disconnects
Ball lock disconnects are the liquid couplers that connect gas and beer lines to the keg posts — grey or red for gas in, black or yellow for liquid out. They’re available in plastic or stainless steel, from KegLand and CMB (Germany), and in standard, barbed, threaded and Duotight push-fit configurations.
The Keg Disconnect Set Inc. JG Fitting covers both gas and liquid connections with John Guest fittings already attached for 3/8″ line – a clean starting point for new builds. The Premium CMB Disconnect Set Inc. JG Fitting is the higher-spec version, manufactured in Germany with swivel action on the line connections to reduce kinking. For brewers running a Duotight dispense setup, the Duotight ball lock disconnects have push-fit outlets built in, keeping the system clean and tool-free throughout. For brewers needing to adapt between different line sizes or connect non-standard fittings to standard ball lock posts, the range also includes Cornelius keg adapters – covering the most common keg adapter configurations used in homebrew setups.
Keg Posts and Poppets
Keg posts are the threaded draft system components on top of the keg that disconnects attach to – gas in and liquid out, each containing a poppet valve that opens under pressure when the disconnect clicks on and seals when it’s removed. Posts wear over time, particularly on heavily used or older refurbished kegs.
AEB Corny Keg Posts are direct replacements for AEB kegs, available as gas in or product out separately. The Multi Post for Cornelius Kegs accepts both gas and liquid disconnects on a single post, which is useful for daisy-chaining kegs or pushing gas down the dip tube for faster force carbonation.
O-Rings, PRVs and Keg Spares
O-rings are the most commonly replaced keg part – lid seals, post O-rings and dip tube O-rings all degrade over time and are usually the first thing to check when a keg is losing pressure or not sealing. The Keg Repair Kit covers the full set of wearable brewery spares in one go: lid O-rings, PRVs, post O-rings, dip tube O-rings and poppets, all packed in a case – worth having on hand rather than hunting down individual parts when something goes wrong mid-session. Note: not suitable for AEB kegs.
Replacement pressure relief valves are available separately in 35psi, 65psi and 100psi ratings. These are safety-critical components; if the PRV on your keg lid is sticking, venting unexpectedly or showing signs of wear, replace it.
Spunding Valves and Carbonation Tools
A spunding valve fits to the gas post of a keg and lets you control internal pressure during active fermentation.
For anyone trying to ferment in a keg, a spunding valve allows pressure to build in a controlled way rather than simply venting off through a blow-off tube. This makes it useful for natural carbonation or capturing CO2 from the tail end of fermentation rather than venting it.
The BlowTie Spunding Valve Kit uses a diaphragm mechanism for more accurate pressure control than traditional spring-based valves, and comes as a complete kit ready to attach to the keg gas post. The Ball Lock Disconnect Spund Valve G2 is a more compact, low-profile option at 4.5cm height — useful where space is tight in a fermentation fridge or chamber.
The Stainless Carbonation and Line Cleaning Cap fits standard PET bottle caps and connects via a ball lock disconnect — handy for carbonating small amounts in PET bottles or as a line cleaning tool when connected to sanitiser.
Dip Tubes
The liquid dip tube runs from the liquid out post to the base of the keg, drawing beer from the bottom. Replacement stainless steel dip tubes are available for 19 litre Cornelius kegs and can be cut down to suit 9 litre kegs where needed – worth replacing on any used keg rebuild or where the existing tube is bent or damaged.
FAQs: Beer Keg Fittings & Keg Accessories
What keg fittings do I need for a corny keg setup?
At a minimum, a corny keg setup needs gas and liquid ball lock disconnects, gas and beer line, and a CO2 regulator. The disconnects are the keg connections and adapters that attach to the posts on top of the keg ( grey or red for gas in, black or yellow for liquid out) – and need to match the line size you’re running (3/8″ for most homebrew setups).
Beyond the basics, O-rings, pressure relief valves and poppet valves are the parts most likely to need replacing over time and worth keeping as spares. The Keg Disconnect Set Inc. JG Fitting is a practical starting point for new builds, covering both gas and liquid keg connections with John Guest fittings already attached.
How do I know if my keg O-rings need replacing?
The clearest sign is a keg that won’t hold pressure. If you’re losing CO2 overnight with no obvious leak at the disconnects or posts, the lid O-ring is usually the first place to check. A spray of no rinse sanitiser or washing-up liquid solution around the lid seal, posts and disconnects while the keg is pressurised will show up any leak as bubbles.
Post O-rings and dip tube O-rings can cause slower leaks that are harder to trace. O-rings are cheap and straightforward to replace – the Keg Repair Kit covers the full set of wearable corny keg fittings in one go, which is the most practical way to rebuild a leaking or used keg properly.
Are corny keg fittings universal across different keg brands?
Most ball lock keg fittings are broadly compatible across Cornelius-style kegs, but there are differences worth knowing about. AEB kegs use slightly different post threading to standard Cornelius posts, which means some generic replacement posts and repair kits are not suitable.
Ball lock disconnects are generally universal as they connect to the post rather than threading into the keg body. If you’re unsure about compatibility for a specific keg part, the product listings include compatibility notes – or drop The Malt Miller a message and the team will point you in the right direction.
Where can I buy keg fittings and beer keg accessories in the UK?
You can buy keg fittings and corny keg accessories at The Malt Miller — ball lock disconnects, keg posts, O-rings, PRVs, spunding valves, dip tubes and keg repair kits, all stocked for homebrew Cornelius and ball lock keg setups.
Alongside the beer keg fittings you’ll find CO2 regulators, gas line, push fit fittings and the rest of the draft system components needed to build or maintain a complete home keg setup.
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