What is an ash catcher and what does it do? The ash catcher is an adapter that functions by filtering the smoke and reducing the amount of tar that enters the main chamber of the water pipe. An ash catcher's purpose is to prevent debris from ending up in your water. A glass ash catcher is ideal as its transparency allows you to see exactly what is being kept out of the water. Ash catchers for bongs come in many different sizes, styles, and colors from which to choose. How do you use the ash catcher bowl? The ash catcher bowl goes on top and slides directly into the ash catcher. You will light up the weed in your bowl as usual, knowing that the ash catcher will keep everything clean and neat.