How do I measure my pipe’s downstem?
What size downstem do I need for my pipe, you might ask? Downstems are sold with two dimensions in mind: the length of the downstem, and the size of the joint in which the downstem will fit.
To find out the best length of your downstem (aside from buying multiple downstems of different sizes and trying them out), you can use a pencil or pen. Stick the pencil inside your bong through the joint until the tip (where all the diffusion holes would be) are completely submerged in water. The downstem is likely around one inch above the bottom of the bong. At this point, mark where the pencil leaves the joint. Take the pencil out, and measure how many inches from the mark to the pencil tip, in half inch increments--that’s how long of a downstem your bong needs!
Additionally, you’ll need to know the joint diameter of your bong, of which there are three main sizes for bong joints: 10mm, 14mm and 18mm. 10mm are uncommon and are usually for mini rigs. The joint sizes refer to the width or diameter of the joint, so these are pretty easy to measure compared to a downstem’s length--just grab a ruler and see how many millimeters across the joint is. Once you have this info, you’re ready to get the right downstem for your bong.
If you’re considering buying a new bong and are looking into downstem choices, do consider that while mini rigs are more portable and take up less space, 10mm joints don’t have as many accessories available as do the more common 14mm and 18mm. Also, the smaller the joint, the faster the downstem will clog. 18mm joints mean a slightly wider downstem that won’t fill up with resin as quickly as a smaller jointed downstem.