Keg Coupler Types: A, D, G, S and U Guide
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A keg coupler, also called a tapping head, connects a draught keg to the gas and beer lines. It allows gas to enter the keg and beer to leave it while keeping the system sealed and pressurised. The important part is compatibility: the coupler must match the valve fitted to the particular keg.
This guide explains how a keg coupler works and compares the A, D, G, S and U keg coupler types commonly encountered by home bars, venues and event operators in Ireland. You can also browse all available keg couplers and tapping heads from TheKegCru.
How Does a Keg Coupler Work?
The keg valve and coupler work like a lock and key. When the correct coupler is fitted and engaged, its probes open the keg valve. One connection allows dispense gas to enter the keg; the other lets beer travel through the beer line towards the cooler and tap.
The gas does not simply create bubbles. It supplies the pressure needed to move the beer while helping to maintain the beer's intended condition. Standard lagers, ales and ciders are commonly dispensed with CO₂, while Guinness Draught and other nitrogenated stouts require the gas and equipment specified for that product. Read our beer gas versus CO₂ guide before connecting a new system.
Keg Coupler Types and Compatibility
The table below gives useful Irish-market examples, but it is not a guarantee for every keg carrying a particular brand name. Breweries can use different valves for different products, keg formats or markets. Always confirm the required coupler on the individual keg listing or with the keg supplier before ordering equipment.
| Coupler type | Common examples | What to check |
|---|---|---|
| A type | Used by some German and European keg formats, including compatible Paulaner kegs | Confirm that the specific keg uses an A-system valve; do not choose it from the country or beer style alone |
| D type | Used by compatible D-system kegs, including the Budweiser keg format supplied for the matching TheKegCru coupler | Often associated with American Sankey systems, but compatibility still needs to be checked for the exact keg |
| G type | Used by compatible G-system kegs, including Grolsch formats | The head profile differs from A, D, S and U systems, so a similar appearance does not make them interchangeable |
| S type | Used by many European keg formats, including compatible Heineken and Carlsberg kegs | Where Type 1 and Type 2 versions are listed, match the precise specification required by your equipment and keg |
| U type | Guinness Draught and other compatible U-system kegs | For the Guinness kegs supplied by TheKegCru, use the specified U-type connection |
A Type Keg Coupler
The A-system is used on selected European keg valves. The TheKegCru A-type product is associated with compatible Paulaner formats, but that does not mean every German beer or every Paulaner package automatically uses the same valve. Check the keg description first and view the current selection in our tapping-head collection.
D Type Keg Coupler
The D-system is frequently called an American Sankey connection. The D-type keg coupler sold by TheKegCru is intended for compatible D-system kegs. Never try to make an S or D coupler fit the other valve by applying extra force; although the systems can look similar, their probe dimensions differ.
G Type Keg Coupler
A G-system coupler connects to compatible G-style keg valves. Our G-type keg coupler is associated with compatible Grolsch keg formats. Confirm the valve before purchasing, particularly when a keg was sourced outside Ireland.
S Type Keg Coupler
The S-system is widely used for European draught beer. The active S-type keg coupler listing covers compatible S-system formats including Heineken and Carlsberg. Some equipment listings distinguish between Type 1 and Type 2 versions, so match the exact product specification rather than relying only on the letter S.
U Type Coupler for Guinness
The Guinness Draught kegs supplied by TheKegCru use a U-system connection. Choose the U-type Guinness keg coupler and combine it with the correct stout tap, regulator and 75% nitrogen/25% CO₂ mixed gas. Our Guinness keg setup guide explains the complete Irish home system, including the correct 35–38 PSI setting.
How to Connect a Keg Coupler
- Confirm the coupler type against the exact keg.
- Secure the gas cylinder upright and make sure the gas supply is closed before connecting equipment.
- Connect the gas line to the coupler's gas inlet and the beer line to its beer outlet.
- Check that the washer, seals and fittings are clean, present and undamaged.
- With the coupler handle raised, align the coupler with the keg valve and lock it into position as directed for that coupler type.
- Engage the handle, open the gas supply slowly and check every connection for leaks.
- Set the pressure recommended for the beer and dispense system rather than copying a setting from a different product.
Use food-grade line and suitable connectors from our beer-line fittings and beer and gas line ranges. Never disconnect or dismantle fittings while the system is pressurised.
Which Side Is Gas and Which Side Is Beer?
On a typical keg coupler, the vertical top outlet carries beer and the side inlet receives gas. However, follow the markings and instructions supplied with the actual coupler. Reversing the lines can stop the system working correctly and may force beer into equipment intended only for gas.
Coupler Cleaning and Maintenance
Beer-contact surfaces need regular cleaning. Disconnect and depressurise the system safely, then clean the coupler, beer line and tap using approved draught-line cleaning products. Inspect washers and seals for wear, keep the pressure-relief mechanism free of residue and replace damaged parts.
A dirty coupler can affect flavour, restrict flow and contaminate freshly tapped beer. Cleaning the tap alone is not enough because the coupler is part of the same product path.
How to Choose the Right Keg Coupler
Start with the keg, not the beer style. Find the exact product in the large-keg collection, check its listed coupler requirement and then select the matching tapping head. If the information is unclear, contact TheKegCru with the full keg name and size before ordering. This is safer and cheaper than guessing from the brand logo.