Smoking a bong begins at the bowl-tip of a bong. However, the mechanics of a bong begin at the reverse side where the mouthpiece is. When you put the mouthpiece on your mouth and slowly and carefully begin to inhale, you’re creating a vacuum inside the bong between the water and your mouth. It works like you’re trying to draw the water over the straw.
After that, once you add flame to the weed inside the bowl, the smoke produced out of it will flow over the downstem and go to the base of your bong. That is where the bong does the magic. Here, the water is quite heavy compared to the smoke. Hence, the smoke will elevate while the water will stay the way it is.
You will see yourself attempting to suck and absorb the contents of the bong over the tube. The smoke rises, going through where you’re trying to suck up. The separation between the smoke and water comes with a 2-fold effect: it cools and filters the cannabis smoke.
While the smoke is passing over the water within the base, so the water is acting as the filter or net that traps and eliminates the unwanted particles like tar and ash.