carbonation nation: a step-by-step guide to home carbonation
the goal?       fully carbonated water (or other beverages)
the cost?       about $300 up-front, and pennies per bottle,
the process(1) freeze about 1/5 of a (plastic!) bottle's worth of water ahead of time. for the freezing, use a normal bottle cap (not shown). (there is no need to be concerned about the bottle breaking in the freezer, since the volume of water is so much smaller than the bottle's volume.)   the goal of this step is to allow for the water that will be added to the bottle to be rapidly cooled to near-zero degrees celcius.
(2) fill the bottle nearly to the top with tap water, leaving a couple inches of airspace so that the contents of the bottle can be easily mixed.   attach the carbonator.   to remove all air from the bottle, squeeze the bottle while using a fingernail to press the silver release valve on the top of the carbonator.   once water starts coming out, release the valve.   this step eliminates air from the bottle, creating space for CO2.
a bottle after screwing on the carbonator                    the same bottle after expelling the air
(3) open the main valve on the tank.   (this is the big, obvious handle; turn counter-clockwise to open.)
note the pressure.   when the main valve is open, the gauge at left shows the pressure of the tank itself, serving as an indicator of the remaining gas in the tank.   the gauge at right shows the pressure outside of the regulator's main control valve (but inside the red-handled valve). this latter gauge (on the right), in other words, is telling you what the pressure inside your bottle will be once connected.   for strong carbonation, 45 psi is more than enough.
some regulators (such as the one pictured) do not allow the pressure to be set above 50 psi or so. this is a safety mechanism. with higher pressures, you will run the risk of your bottle exploding (which has never been a problem for me at 45-50 psi).
(4) open the auxiliary valve, if your regulator has one. (this is the red-handled valve.)
valve closed                                                                         valve open
(5) attach the beverage adapter to the carbonator. (this can be tricky your first time, although it's a cinch once you know how.)
first, hang the adapter on the carbonator as shown at left. then, with the bottle on a counter top, use the base of one palm to push the adapter down onto the carbonator until you hear a soft "pop" as the bottle expands from the pressure of the injected gas (as shown at right).
as you are pushing down with one palm, use your other hand to pull down on the movable base of the beverage adapter. the goal here is to lock the adapter onto the carbonator. (you can confirm that you have locked on the adapter because if you shake the bottle, the bottle will maintain it's internal pressure.)
with the adapter stably attached, turn the bottle on its side (so that it's long axis is parallel with the floor). shake vigorously for 10-20 seconds.
the beverage adapter, not quite on                             the beverage adapter, fully on
(note that the base of the adapter has moved!)
(4) remove the beverage adapter (but not the carbonator). the bottle may now be stored in a refrigerator, and it will maintain it's pressure. to enjoy, just remove the carbonator.
notably, if you are going to be storing the bottle in the fridge, there is an important additional consideration. you ideally want to start with enough ice so that just as you have finished the carbonation process, all the ice has melted.   the more ice that remains, the lower the pressure will be inside the bottle when the ice inevitably melts.   once you've figured out empirically how much ice this is, you can draw a fill line on your bottles to make the process really easy.
the initial investment
i purchased the following items online from northern brewer:
5 carbonators (#k026)
2 beverage adapters (Ball Disc 1/4 Barb Gas) (#k012)
2 feet of tubing (Bev Tubing, 1/4 x 1/2) (#k025)
2 screw-on clamps (S/S Worm Gear Clamp #1 1/8" - 1/2" OD) (#k124)
1 CO2 regulator (#k003)
the total cost of the above items was about $160.   in addition, a 20 lb tank set me back $150 from airgas, but i'm sure you can find a better deal. the tanks are heavy (20 lbs refers to the weight of the gas in a full tank, and the tank itself is even heavier), so the shipping can kill you.   on the other hand, if you don't have a brewery supply store, welding supply store, or industrial gas store in town, ebay is a definite option.
these six items (tank, plus five items listed above) are all you'll need, beyond a screwdriver, some plastic bottles, and a freezer.
you could certainly make-do with fewer carbonators, but i find it much more convenient to have enough so that i can always have several bottles in my fridge.
admittedly, $300 is a big up-front cost, but keep in mind that once the system is in place, the marginal cost of each carbonated bottle is on the order of pennies.   this is because tank refills/exchanges are cheap ($20-$30), and each fill of the tank can fill thousands of bottles.   drink a couple hundred bottles, and you're even.
safetyawareness of safety issues is important.
tanks can become missiles if a regulator is wrested loose (after being dropped or knocked over). in addition, if a (small, poorly ventilated) space were to fill with CO2, it would be lethal, although i do not know of such an accident ever happening.
the act of using the methods described here on this page does not make me responsible for your safety. you must be responsible for your own safety!
if you've never used a gas regulator, have someone show you the basics before you take a tank home. if you follow some simple, basic rules, you'll likely be fine.   for example:
(1) introduce yourself to basic gas tank safety.
(2) transport or move a tank only with the regulator off and with a protective cap screwed on over the main valve.
(3) be sure the tank is secured in position so that if the tank suddenly releases gas, it won't go flying across a room. typically chains are used for this purpose.
(4) take care in installing or removing a regulator.   make sure the regulator is on tightly before opening the tank's main valve.   before removing a regulator, make sure the tank's main valve is closed.   never transport or move a tank with the regulator attached.
summary and linksin summary, there is a big up-front cost, but the cost of each carbonated bottle, excluding the original investment, is on the order of a few pennies.     this homemade system works extremely well and is far cheaper in the long run than the commercial systems or buying bottled water.
my goal in making this guide was to provide a more illustrated and how-to-oriented description of a solution i cobbled together by combining information from the following two links. the first link concisely lays out the concept:
cool tools home carbonation system
this second link has more details, including some of the science required to understand the process, which is pretty informative. one specific point about this site: i found it difficult to understand from this page alone exactly how the clamp-in tire valve kit would work as a means of attaching the hose to a bottle. the carbonator, on the other hand, is very simple, albeit perhaps pricier. in my view simplicity is worth the extra tens of dollars up-front
richard j. kinch's carbonating at home
feedback of any kind is much-appreciated: jmgray [at] foo dot net.