There are a few things you can do to clean a keg before you serve it.

  1. Remove the top of the keg and unscrew it so that the beer can flow freely. Pour some water into a pot and set it on the stove to boil. When the water boils, pour it over the keg and let it cool for about 10 minutes. Pour a layer of baking soda over the top of the boiling water. Let it sit for another 10 minutes, then screw on the top of the keg and put it back in place.
  2. Use a plunger to push out any liquid that has built up in the bottom of the keg over time. This will help to clean out any trapped air or gas bubbles.
  3. Use a vacuum cleaner with hose to suck out all of the dirt, dust, and other debris that has built up inside of your keg over time.