Downstem

A downstem is the straight glass tube that runs vertically to connect a bong or dab rig's main bowl or nail attachment to the base water chamber below. It pulls air through the heated material in the bowl down into the water to create suction, diffusion and filtration effects. Downstems are commonly either fixed permanently to the piece or made removable for easy cleaning and replacement. The downstem enables smooth, cooled hits from water pipes. Smoke initially travels from the freshly ignited material in the heated bowl down through the downstem, where it percolates through the water in bubbles before traveling up the main chamber to the mouthpiece for inhalation. The length of the downstem impacts the level of diffusion, filtration and draw resistance. Removable downstems allow for simplified cleaning and substituting in new styles, but it's critical to get an airtight fit with no leaks. Proper airflow relies on the downstem forming a snug, sealed connection between the base and the bowl or nail. A quality downstem diffuses smoke optimally while avoiding excess drag.