If you've ever rented a keg and found that the tap won't connect, you already know why keg coupler types matter. There are several different valve standards used around the world, and the coupler—the fitting that locks your tap line onto the keg—has to match the valve on your specific keg. Get it wrong and you'll get nothing, or worse, a pressurized spray of beer the moment you try to disconnect it.
Here's a plain-language breakdown of the four coupler types you're most likely to encounter when ordering kegs in the Bay Area.
D System: The American Sankey
The D system, also called the American Sankey coupler, is the most common tap fitting in the United States. If you're serving a domestic craft beer or a major American brand, you're almost certainly using a D system. That includes most of the local breweries we carry with pride: Fort Point, Almanac, Anchor, Drake's, and Calicraft all keg their beers with a D system valve. So do the big nationals—Budweiser, Coors, Miller, PBR.
Most home kegerators sold in the US ship with a D system coupler by default, which makes sense: it covers the vast majority of kegs you'll ever order from a San Francisco shop.
S System: European Sankey
The S system looks almost identical to the D system at first glance, but the probe that inserts into the keg valve is slightly longer and narrower. It's used by most—not all—European imports: Stella Artois, Heineken, Amstel, Pilsner Urquell, Newcastle, Leffe, and St. Pauli Girl all use S system valves.
The key thing to remember: a D coupler will not properly connect to a European Sankey keg, and an S coupler on an American keg is just as problematic. If you're planning a party with a European lager on tap, confirm your setup has the right coupler before the keg arrives.
A System: German Slider
The A system—often called the German Slider—uses a sliding latch mechanism rather than the lever you'd find on a D or S coupler, which is the quickest way to tell them apart. It's the standard for most German beers and a number of Belgian brands: Paulaner, Warsteiner, Bitburger, Krombacher, Löwenbäu, Franziskaner, and Hoegaarden all use A system valves.
If you have a soft spot for Bavarian wheat beers or German pilsners on draft, this is the coupler to know about.
U System: The Guinness Coupler
The U system is used almost exclusively by Irish brands—Guinness, Harp Lager, Smithwick's, and Magners Cider among them. The valve design is distinctive and won't accept any other coupler type; likewise, a U system coupler won't connect to any other keg valve.
One more thing worth knowing about Guinness on draft: beyond the coupler, a proper pour also requires a nitrogen/CO2 blend gas rather than straight CO2. That's what gives Guinness its characteristic cascading pour and thick head. It's a separate piece of equipment from the coupler itself, but something to plan for if you're setting up a nitro tap.
Quick Reference: Which System for Which Beer?
| System | Also Known As | Common Brands |
|---|---|---|
| D | American Sankey | Budweiser, Coors, Miller, PBR, Anchor, Fort Point, Almanac, Drake's, most US craft |
| S | European Sankey | Heineken, Stella Artois, Amstel, Pilsner Urquell, Newcastle, Leffe |
| A | German Slider | Paulaner, Warsteiner, Bitburger, Hoegaarden, Franziskaner, Löwenbäu |
| U | Irish/Guinness | Guinness, Harp, Smithwick's, Magners Cider |
How We Handle It at Mike's
When you rent a keg from us, we match the right coupler to your keg before it leaves the store. You don't need to memorize the chart above—just tell us what you want to pour and we'll sort out the hardware. We've been doing this on Mission St since 1959, so we've matched a few couplers in our time.
If you're setting up a permanent home kegerator or a tap system at your office or restaurant, it helps to know your preferred beer's coupler type before you buy equipment. Take a look at our keg equipment and services page to see what we offer, and browse our full keg selection to plan your order.
Not sure where to start on the beer side? Our beer collection covers everything from local craft cans to major imports. Stop by the store on Mission St, give us a call, or place your order online—keg delivery across San Francisco is available for orders placed by 9 AM (same-day), with an $8 flat delivery fee and a $125 order minimum. We also deliver to the East Bay on Tuesdays and the South Bay on Wednesdays.
What happens if I use the wrong coupler on a keg?
In most cases the coupler simply won't seat properly and no beer will flow. If it partially connects under pressure, you risk a forceful spray of beer when you try to disconnect it. Always confirm the keg's valve type before attaching any coupler.
Do I need special equipment to pour Guinness on draft?
Yes—two things. First, a U system coupler to match Guinness's keg valve. Second, a nitrogen/CO2 blend gas (typically around 75% N2 / 25% CO2) rather than straight CO2. The mixed gas is what creates the characteristic cascading pour and dense head that Guinness is known for.
Can I rent a coupler along with my keg at Mike's?
Yes. Keg rentals from Mike's Liquors include the correct coupler for your beer—we'll confirm the right fit before your keg goes out the door. See our equipment and services page for details on keg rentals and deposit information.