I have a bong with a 10mm downstem/bowl combo (the downstem and the bowl are not separate), but unfortunately, it's broken. The downstem part is still intact, but the bowl part of it is broken. I have been trying really hard to figure out a solution, but I haven't been able to. I live in Tamale, Ghana, and they actually don't have head shops around here, so it's impossible to buy a replacement downstem. I've posted this a couple of times, and it seems that every time people ignore my post, and they say, "Just go out and buy a new downstem" when I made it clear that it is just not possible to do so. So is there no way to use something in place of a downstem? The only other way to smoke here in Ghana is joints, but I'm terrible at rolling, and it's a pain in the ass anyway. Vaporizers are unattainable as well, so it seems that I am out of luck.
Head off to the local hardware store or junkyard if that is your options. You'll need to fabricate a new downstem and bowl. Brass or steel fittings will do it. Something like a 3/8th to 1/2 inch bell adaptor for the bowl. A short threaded section of pipe. For the taper I'd carve a wooden plug that fits the taper and drill it for the pipe . Wind up with something shaped like this. BNW
