It's imperative that you dump that motherfucker each and every time. Sometimes, you may need to take a break during a session to freshen-up your piece. For example, saturday night, about 6 of my friends came over, and we were all smoking out of the same bong, an old glass standby I bought at a flea market when I was in Portland a few years ago.

Anyway, after about 5 grams, the water was fucked-up, and the inside of the bong smelled terrible. It was so bad that I felt physically sick from the stench, so I just walked it into the kitchen, gave it a quick scrub and rinse, then refilled it. Problem solved.

Sometimes, I like to put a few drops of mint oil in the water to give it a smooth finish.