Seth - BS to your magic carbonator SODA has see DIY
• A CO2 tank of any size. Empties can be found on eBay and filled at welding shops, paintball facilities, homebrew hobby shops and elsewhere. My five-pound tank was $100 filled at McKinney Welding Supply in Manhattan and fits into a small cabinet in my kitchen.
• A gas regulator ($39.95, Amazon). The regulator tames the high-pressure inside the CO2 tank and outputs an even flow of gas at constant, adjustable pressure into whatever you connect to the other end. Nicer ones will have two gauges—one for the gas tank's pressure which will hit zero when empty, and one that measures the output pressure into whatever you're gassing up.
• A length of vinyl tubing (Five ft. with hose clamps, $5.49, Amazon). Tubing rated for pressurized applications is required—you'll want about a 1/4" thickness. You can also get braided vinyl line for a bit more durability. The barb fitting of a CO2 regulator typically has an outer diameter of 3/8 inch, so tubing with an inner diameter of 5/16 inch is what you want.
• A ball-lock keg coupler ($7.50, Amazon). This piece connects to the other end of your tubing and holds back gas flow until the little inner valve button is depressed by the tip your Carbonator bottle cap.
• The Carbonator bottle cap ($11.43, Amazon). This ingenious cap screws onto your soda bottle and provides a valve on the other end that engages with the keg coupler to connect your bottle to the gas supply without leaks.
• A standard soda bottle filled with cold liquid (warm water doesn't dissolve CO2 well). Any size bottle will work, so long as it has the common cap size found on a typical two-liter bottle of Coke. I can't resist quoting Kinch again here, who very admirably takes nothing in his system for granted: "If we could send a few back through time to the ancients, these bottles would be considered precious jewels reserved for the king's use."
Total cost: $163.94. It's a little more money up front than all but the most pricey Sodastream machines, but thos