First, yes I realize this thread is nearly 6 months old, so I hope the originator might be still watching. I carbonate water one liter at a time. All I use is a 10 pound cylinder of carbon dioxide with the valve set at about 28 pounds, and a hose about 18 inches log to a cap that fits my bottles, which are simply empty soda bottles. I chill the water so there is a small amount of ice inside. Carbonation takes about 3 or 4 minutes. The key, in my view, is that I shake the bottle during the carbonation process. Obviously one cannot do that with a significantly large container, but one liter is about my daily consumption.
As a little add on information, the last time I had the gas tank filled it cost about $40.00. Since that time I have kept a tally of bottles carbonated. As of yesterday I am up to 358. About 6 more and the cost per bottle will be down to 11 cents. I hope, and expect, to drop that to under 7 cents by the time the tank is empty.