A beer keg is a large pressurised steel container for holding beer. Many home brewers purchase used kegs to put their own brew into, saving them the trouble of washing and sterilising bottles every time they wish to brew some beer. If you have purchased a used keg, the first thing you will want to do before washing and sterilising the keg is to depressurise it. Depressurising a keg is quite simple, it is the same process as tapping a fresh keg.
Check to ensure that you have the right tap for your keg. If you are unsure, ask what tap the keg takes while purchasing it, or call on an experienced home brewer friend to come over and have a look.
Press the end of the tap into the round opening located on top of the keg. Line up the notches that are on the keg opening with those on the tap.
Turn the tap clockwise until you feel it lock into position.
Push down the lever on the tap.
Hold down the small lever on the nozzle exactly as if you were filling a beer. Do this until no air comes out, this indicates that the tank is now depressurised.
If you simply want to depressurise a keg for drinking, follow the instructions above, but stop once beer starts to come out. After this pump the keg until beer comes out the nozzle at the desired pressure.
Do not push down the lever until the tap is locked into place.