Beer taps are specially designed valves used to open a keg of beer and control the flow of beer from the keg to your cup. While all tap systems are comprised of a pump and hose dispenser, the tap coupler is the most important component in that it must match the hole on the top of the keg in order for the tap to work. The most common coupler systems are the American "D system" and the European "S system." With the right tap system, pump and tap handle, you can put together a homemade beer tap in a matter of minutes.
Call your local keg distributor before you purchase your tap coupler system to verify the coupler system type they use. The system types you can expect are: D, S, European U, G, M, A, and twin probe. Each system differs in the design of its valve connection. If you have the wrong coupler, you simply will not be able to connect the coupler to the keg or be able to open the flow of beer into the pump section of the tap.
Attach the manual or electric pump to the top of the coupler and hose distributor to the side port of the coupler. This set-up is ideal for free-standing kegs that need to be portable.
Carbon dioxide pumps are useful in fixed draft set-ups where the keg stays in one place and will deliver beer to a faucet or beer tower. If this is what you require, attach the carbon dioxide canister and regulator to the side port of the tap coupler with a plastic air line. Screw the beer line to the top of the coupler and run that line to the faucet or beer tower where it will be screwed onto that unit.
Attach the tap coupler, with pump and hoses attached, to the top of the keg by pressing down firmly while twisting the coupler until it locks into place. If you're using a draft system, screw your tap handle to the beer tower or faucet. You've now pieced together a homemade beer tap system to get your beer out of the keg and into your cup.