Kegging is great for soda, seeing that the kegs a brewer uses for beer used to contain soda. We will point out that it is a good idea to dedicate a keg solely for soda as the soda flavor does tend to work itself into the plastic o-rings inside the keg. If you do want to switch back to beer, just take the keg apart and soak everything, or buy new o-rings. We are going to assume that you are making 4-5 gallons of soda at a time. Smaller amounts will take less time to carbonate. Now onto the process:
Keg Carbonation Process
1) Clean Keg
2) Sanitize keg
3) Fill keg with soda
4) Turn pressure gauge up to 25-30 p.s.i. (25 p.s.i. for Sprecher, 30 p.s.i. for any Extract Soda), and leave gas on.
5) After 3-5 days, turn pressure down to 15 p.s.i., and taste the soda. If the soda is still flat, turn the pressure back up to 25 p.s.i. for 24 hours and try again
Soda takes longer than beer to carbonate due to how heavy the liquid is. It takes the CO2 longer to infuse with the soda due to the weight. Once you carbonate one in the keg, the soda should stay pretty consistent as to the amount of time it takes to carbonate, so just pay attention to how many days it took so you will know for next time. Like beer, soda will carbonate quicker in the refrigerator than at room temperature. The colder temp allows the CO2 to absorb quicker. Soda is also dispensed at a higher p.s.i. than beer. You want your pressure set at 5-10 p.s.i. for best results.