What is their function and how does it work? I'm actually asking for my friend and he already ordered a bong with a percolator, so I don't really need the pros/cons because the decision has been made but we both want to know the purpose of it.
there's a central arm that allows the smoke to pass from the bottom chamber (where the diffy/downstem is) into the second chamber. if your buddy got a tree perc, the smoke will then be distributed from that central arm into x amount of arms coming off the central arm. there are slits cut on each arm that allow the smoke to exit the small arms and interact with the water. the smoke then goes up into your mouth/into next perc chamber. if he got a dome perc then the smoke comes up the central arm like in a tree, but then rather than getting distributed it just comes out of the arm and into the dome where there are slits cut on the bottom. smoke exits the dome from the bottom slits (interacting with the water) and then rises. the interction with the water allows the smoke to be cooled down