Our DIY carbonator is going to be very simple. We just need a tank to store our carbonating target that is capable of being pressurized to about 100 PSI. Rich Faulhaber over at Evil Mad Scientist Labs was nice enough to share the idea of using a water filter housing. Check out www.evilmadscientist.com/article.php/co2inator to see how he did it. Follow on to the next steps to see my take on it.
Step 1: The CO2 Tank
The remote supply line makes this setup easy. One side screws onto the tank and the other usually has a quick connect system. I couldn't find fittings that would adapt the quick connect to the plumbing fittings on the water filter housing, so I just cut the paintball quick connect fastener off. With that out of the way, just use a barb fitting and a standard air compressor quick connect fitting to make things work with the water filter housing.
Be sure to use teflon tape on the threads of all connections to prevent leaks!
Step 2: The Pressure Vessel
Different filter housings have different connections, so this next part is going to be a bit vague. You need to find a way to plug one side of the filter housing and convert the other to the air compressor quick connect. For my filter housing it took the following fittings:
1 - 1" to 3/4" adapter
1 - 3/4" to 3/8" adapter
1 - 3/8" to 1/4" adapter
1 - air compressor quick connect recpticle
1 - 1" plug fitting
In the pictures you can see that I have some steel connectors and adapters, which is bad. You should only use brass fittings to prevent corrosion.
Another important addition to what you see in the pictures would be a pressure gauge. It would be easy to attach a pressure gauge to the plugged side of the water filter housing. Without the pressure gauge you don't know if you're over-pressurizing the housing, which is very dangerous. Be safe and get a pressure gauge!
Step 3: Using the Carbonator
If your pressure vessel is clear like mine you can see a lesson that every deep sea diver knows well. The bends, decompression sickness, divers' disease, caisson disease, whatever you want to call it, it's bad news. If you release the pressure from your system too fast the skin of your fruit will break open and bubbles will squirt out everywhere. The rapid release of pressure is more than the fruit can take. This is the same thing that happens to a diver's body if they surface from the bottom of the ocean too fast. The pressurized nitrogen in their body tries to escape any way it can, and that usually is through the blood vessels. Unlike a diver, your fruit will still be useful after suffering from the bends. It will just make a big mess inside the pressure vessel.
That's all there is to the DIY carbonator. I've filled my pressure vessel 5 times and still haven't ran out of CO2, so a 20 oz tank of CO2 can get you through lots of parties or curious children. Please be very careful when working with pressurized gasses and foods. Make sure your equipment is clean and free of oils, debris, metal shavings, and other harmful items. Use a pressure regulator or at least a pressure gauge to make sure you don't over-pressurize the water filter housing, 100 PSI is more than enough to carbonate anything this type of pressure vessel can handle. Be safe and have fun!