If your friends and family are anything like mine, you've observed that home beverage carbonation is experiencing a bit of a renaissance lately. Perhaps you've seen the increasingly ubiquitous Sodastream machine on a countertop near you—or, more likely, heard its syncopated honk and pop-fizz release from across the room, announcing another fresh liter of water made bubbly.
The Sodastream is a nice machine in a convenient package, but for the true fizz addict with a tinkerer's predilection, it's possible to build your own home carbonator that's cheaper, more flexible, and ultimately more satisfying. Here's why you might want to consider your own DIY rig, and most importantly, how to put it together. It's easy!
The Sodastream machine's Achilles heel is its tiny, proprietary CO2 tank. The company (formerly known as Soda Club) sells seven different home carbonation machines ranging from $80 to $200 (enhancements along the line are mostly cosmetic), but only offers CO2 canisters in 14.5 and 33-ounce sizes. (The measurements refer to the weight of the gas.) Sodastream claims somewhat optimistically that these are good to make a total of 60 and 130 liters of seltzer respectively. What's worse, these tanks have a proprietary cap which can only be filled by the company. My local kitchen supply store charges a hefty $15 to swap an empty 14.5-ounce tank for a new one. Compare that to the $15 charged by my friendly neighborhood welding supply shop to fill my new five pound tank, and the economics start to come into focus. With luck, my five-pounder won't need a refill until early 2013, and if you've got the room, you can go even bigger on the tank. Web carbonation guru Richard Kinch yields over 1,000 liters from his 20-pound tank—and he likes his seltzer extremely fizzy (more on that in a minute).
The Sodastream is an appealingly simple gadget. But once you develop a refined taste for on-demand seltzer, you may find it somewhat limiting. Sodastream's CO2 regulators come factory-set and aren't adjustable, meaning it's impossible to go beyond its pre-defined pressure limit. But with your home-built model's adjustable regulator, you can fine-tune the level of carbonation applied to your liquids. Mr. Kinch favors a tongue-blistering 45-50 psi fizz on his soda water, but if you want a milder 30 psi pop, you can adjust your gas regulator with the quick turn of a screwdriver or wrench. Adjustable pressure also allows you to apply the ideal amount of carbonation to different types of liquids. If you're charging up a batch of tasty gin fizzes (or starting your own modernist cocktail bar), you'll want to dial up the pressure to 45 psi, since alcohol can dissolve more carbon dioxide than plain water. I don't know the ideal pressurization level for cream gravy, but with your bountiful supply of cheap CO2, you're welcome to experiment (please report back with your findings).
With a home rig you can also ditch the Sodastream's proprietary one-liter plastic (or puny 620ml glass) bottles and use anything with a standard plastic soda bottle cap. One liter, two liters—even those cartoonishly obese three-liter bottles—all will work with your DIY carbonator. Just make sure it's plastic—a blown plastic bottle is much preferable to flying glass shrapnel in the unlikely case of rupture.
If you've gotten this far, I probably don't need to explain to you how satisfying it is to improve on a commercial product with a more economical machine of your own construction. But even if this isn't typically your thing (I'm by no means a handyman), a home carbonator is an exceedingly easy project that just about anyone can handle. So let's get started.
• 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 those $15 canister refills add up quickly. After a few months you'll be saving money (ultimately, the system produces seltzer at three or four cents per liter—not bad!). You can also lower your initial spend on the CO2 tank by shopping eBay.
Once you have all your parts, final assembly can be done in 10 minutes or less. Here are the connections you make:
Now, for the grand finale. There are three points of gas control in our system: the tank's main on/off knob, the regulator's cutoff switch (right above the barb end (some regulators don't have this)), and the valve on your keg coupler. Gas only flows through the system when the Carbonator cap is snapped into the keg coupler (you can also reach inside the coupler and depress the valve with your finger if you want to torment the cats with a gust of CO2). If you fill bottles frequently, you can leave the tank's main on/off valve open and use the regulator's cutoff switch to turn the gas on and off.
And that's it! May you enjoy a long life of flexible, thrifty carbonation with your own home rig.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.