A downpipe or downstem is an essential part of a bong or water pipe. It is often called a chillum. A glass chillum is a downstem with a bowl. The use of a screen or pipe gauze is recommended. A metal downpipe is often used in ceramic and acrylic bongs and usually the bowl can be unscrewed.
Buying a Downpipe for a Bong / Water Pipe
Take into account the dimensions regarding the connections of your bong, downpipe, adapter and bowl. The most common sizes are 14.5MM and 18.8MM, also referred to as joint size (SG14) and (SG19).