I'm planning on building a simple CO2 rig for carbonating water and any other drink/fruit. It will be similar in cost to getting an off the shelf soda maker like sodastream, but more powerful, more flexible, and with lower operating cost. Components: 5 lb CO2 tank, 2-gauge pressure regulator, tubing, and a keg-style ball-lock connector. Using a cheap cap called "The Carbonator," I can hook it up to PET bottles, but I mostly plan to use a gas-side ball-lock connector from "The Kegging Part" to attach the rig to a whipping siphon (still for making drinks).
After a while, when I have more spending money, I plan to get a nitrogen tank + a valve adapter so that I can use a similar, nitrogen-based setup to make foams. It's more expensive up front, but I would never have to deal with those tiny gas canisters.
I've been surprised that I have found almost nothing online about adapting whipping siphons to run off of a tank instead of cartridges. Has anyone done this? It seems very useful for a high volume kitchen. From my understanding, the 2-gauge pressure regulator will eliminate safety concerns about over pressurizing the siphon.
A picture of this type of CO2 rig, from popscience, is shown below.
