just an idea: not all bongs are dishwasher safe, dishwasher water can get really hot, and many bongs are works of hand, not certified Pyrex

also depending on size of the bong and design of your dishwasher, the rotating blades may break your bong or screw up your dishwasher

but using the right dishwashing liquid/powder, i doubt u will have a problem with smell.

again generally speaking design of a bong is a in a way thats best cleaned by hand and using a long bottle brush or something similar