Draught Equipment and System Configuarations > Essential Draught System Components > Coupler

Gas flows in and beer flows out of a keg through the coupler.  While this device has many casual names in beer cellars around the country, the industry adopted the term “coupler” as the standard term for the device.

When you attach a coupler to a keg to tap it, a probe on the bottom depresses the keg valve (or ball) and allows CO₂ to enter the keg and apply pressure to the beer.  This forces the beer to travel up the down tube (spear) and drive the beer to the faucet.

Couplers include two types of one-way valves:

• Thomas valve – This valve allows CO₂ to flow into the keg but prevents the beer from backing up into the gas line if gas pressure drops.  This protects the gas regulators from damage. 

• Check valve – When the coupler is disconnected from the keg, this valve prevents beer from the beer line flowing out through the coupler. This prevents beer spillage in keg tapping areas.

A keg coupler should also contain an integral pressure relief valve. If excessive gas pressure were applied to a keg, this valve would open to prevent damage to the keg and coupler.  The valve can also be opened manually and this should be done periodically to test the safety relief valve. The manual release usually looks like a small metal pin fitted with a wire ring.  To test the valve, pull on the ring to slide the pin a short distance out of the coupler and release a small amount of gas.

The diagram below shows all the features of a coupler.

At the time of this writing, most breweries worldwide use one of six variations of the Sankey-brand coupler (see pictures below).  Most U.S. breweries use the Sankey “D” coupler, unless otherwise noted.

While not exhaustive, the following list shows the coupler used by various breweries or brands as of this writing. If in doubt, contact the brand’s distributor to verify the proper coupler types before tapping.

Cut-away of Sankey "D" Coupler

How Coupler Interacts with Keg to Draw Beer

Next topic: Beer Line >