If the downstem of your bong broke, it is not the end of the world. You will first want to look at where and how extensive the damage is. Once you have done this, you can decide how to move forward with repairs.
Assess the Damage
The type of material your bong is made from will play a role. Bongs can be made from glass, ceramic, or plastic. However, acrylic and glass are the two most common types. Acrylic is the easiest type of material for you to repair. If you have a borosilicate heat-resistant glass bong, it can be a lot harder to repair, even if you have a blowtorch on hand.
Sometimes the break will be extremely severe, and it may not be repairable. However, a clean break, chip, or crack can be taken care of using a bit of glue.
Using Duct Tape
If there are clean breaks in the downstem of your bong, you can try using duct tape. Remember that this will work better if there three or fewer pieces to put back together. You will want to clean everything well before starting so the tape will stick well. Then, make sure that it is dry.
Put the pieces together as seamlessly and tightly as possible. Take a piece of duct tape and wrap it tightly around each of the joints. This allows you to keep using your bong, but it is still only a quick fix. That is especially true if you use the piece in water. The downstem of the bong will be thicker where you have the tape. In some cases, you might need to take off the grommet so everything will fit properly. However, the junction will no longer be airless or seamless as it was before.
Use Bonding Agents
A step up from duct tape is to try one of the many bonding agents available. For example, you can look for food-grade epoxy or silicone. That is a longer-term solution than duct tape for the stem. This is also a better option if there are multiple breaks in the piece.
Food-grade silicone is waterproof and nontoxic. You can use it as a sealant, but it does not provide much structural support. You can easily peel it off to remove it. The best place to use it is where the base and the tube meet. You can use it to repair cracks or chips in your glass. But if you frequently handle the area, it might not be quite so useful. You can easily place it over a glue that is not waterproof.
To use food-grade silicone, you will want to clean everything well, making sure that you are careful with the cracks. Then, follow the instructions to prepare the silicone. Carefully spread it along each of the edges and pay attention to the cracks. Now, press the pieces together and wait for it to dry.
For food-grade epoxy, you should make sure that you have smooth, clean edges near the break. If there are jagged edges, you may want to smooth them using a file. Then, you can rub them against fine sandpaper to further smooth them down.
Wipe off any remaining dust from the stem. Then, place the epoxy all along the edges and press everything together. Make sure that you allow it to dry for long enough before you use it. Of course, these are just a few of the industrial-strength products you can use to fix your downstem. But you will want to use them carefully and in well-ventilated areas. They may be damaging to your health.
Other Types of Glue
You can use two-part epoxy, which is made using a mix of hardener and resin. Look for one that bonds to glass and is heat-resistant. This is a long-lasting fix, although you will want to avoid leaving the bonded area submerged. That can cause it to become waterlogged and allow it to leak. You can empty your bong after you use it. It is better to use this method to fix a bong that has a clean break. If there are very jagged edges, you may want to get a glass cutter to make the break cleaner.
Another product you can use is Loctite Glass Glue. It is similar to superglue and can bond to glass easily. It resists both heat and water.
Using a Blowtorch
If you have the right equipment on hand, then a nearly permanent way to fix your downstem is to use a blowtorch. One of the benefits of this method is that it also allows you to attach tiny pieces to the downstem of the bong. However, because of the fire hazard and the extreme temperatures, you may want to leave this to the professionals. If you do decide to do this yourself, it is vital to follow all of the right precautions.
First, you should inspect the parts of the broken stem. It might be necessary to file the edges so they will join cleanly. Next, place part of the stem in a clamp. You can use sturdy tongs for the other piece of the stem. By directing the blue flame to the edge of the piece, you can begin to heat it. Continue doing this until the glass is red.
Press the pieces together and keep torching until you can tell that the pieces are bonding. If you have a small piece, you can use the same method. Allow them to cool at room temperature.
Remember that this method can be dangerous, so take extreme care. You should only use the torch for a removable stem. Remember that the high temperature might make the water chamber crack.
The right method for fixing your stem will depend on the type of break. You could have a professional do it for you. But that can cost quite a bit of money. Depending on how badly damaged it is, you might want to get a new downstem. Of course, you can also save up and get a whole new bong, which might be less likely to break.