home carbonation

I love seltzer, but I don’t love spending money on bottled seltzer and carrying 50lbs of it home at a time. I recently bought a CO2 tank and regulator for the keg at Crushtoberfest, and I’ve been looking for other uses for it ever since.

It turns out that making seltzer at home is very easy, and once you have the basic equipment the cost-per-bottle is extremely low. Here’s how I set it up:

home-made seltzer

The tank and regulator kit are from Micromatic. The rest is just a handful of fittings from McMaster-Carr, screwed into a hole drilled into a seltzer bottle cap. Here’s the parts list:

part #
part source
1 1 5lb. aluminum CO2 tank, empty
2 1 tank filling
local welding supply store
about $10-15
1 double gauge CO2 primary regulator
3′ red vinyl gas hose – 5/16″ ID
2 hose clamps (pack of 10) – part #5388K14 McMaster-Carr
6 1 Brass Barbed Hose Fitting Adapter for 3/8″ Hose ID X 1/8″ NPTF Female Pipe (pack of 10) – part #5346K34 McMaster-Carr
1 Lincoln-Shape Hose Coupling Plug, 1/8″ NPT Male, 1/4 Coupling Size – part #91455K51 McMaster-Carr


1 Lincoln-Shape Hose Coupling Socket, 1/8″ NPT Male, 1/4 Coupling Size – part #91455K52 McMaster-Carr


9 1 Electric Panel Hex Nut 18-8 Stainless Steel, 1/8″-27 Nps – part #91862A306 McMaster-Carr
1 bottle cap
your recycling bin
several empty one, two, or three liter bottles
” ”


* you may need to turn this in for a full tank, although some places will fill your tank while you wait
** I bought a good one, you can get these cheaper
*** unfortunately you sometimes have to buy 10 packs (or more) from McMaster. You can get individual hose clamps from your local hardware store.

Here’s how it goes together:

I drilled a hole in the cap (#10) that was just big enough for the threaded end of the coupling socket (#8) and assembled them together with the nut (#9). I used teflon tape in between parts 6 and 7. I also use my CO2 bottle for a keg when necessary, so I got a second set of part 6 and 8 and attached it to the hose coming from the keg tap. This way I can connect and disconnect from one system to the other.

One thing I learned, and this is VERY IMPORTANT: Apparently there is a chemical reaction between the CO2 dissolved in water and copper (or copper alloys like brass) that creates a toxic substance that will make you sick. Never use brass or other copper-based fittings with seltzer! All of these fittings (or at least the ones that will be in contact with the seltzer for any length of time) are either zinc-plated steel or stainless.

The carbonating process is simple. Fill an empty bottle with the liquid of your choice and refrigerate it. Replace the cap with the special one you made and attach the quick-disconnect hose to it. Make sure the shutoff valve on the regulator is closed, then slowly open the main valve on the tank until the regulator shows pressure. Adjust the output pressure to about 45psi and open the shutoff valve, pressurizing the bottle. Now loosen the cap on the bottle just slightly while squeezing any air space out of the neck of the bottle, then tighten the cap. This will purge any air from the bottle and replace it with CO2. Now shake the bottle vigorously for about 20-30 seconds; this will help dissolve the CO2 into the liquid faster. Shut off the CO2 at the regulator and disconnect the hose from the quick-disconnect fitting. You can now remove the special cap (slowly, the contents are now carbonated!) and replace it with a regular cap.

So on the first day I made seltzer water. On the second day I carbonated apple juice, grape juice, and Gatorade, and ended the evening with a carbonated vodka martini (nice!). What else can I carbonate?

16 Responses to “home carbonation”

  1. Noah Ramon writes:

    Honestly, while it’s using premade parts, I’d recommend replacing parts 6 through 10 with a standard Carbonator cap from Liquid Bread and a ball-lock quick-disconnect – you don’t have to worry about carbonic acid/brass corrosion and you can use the same standard fittings on the hose that you’d use for a corny keg. Otherwise, it’s the same procedure down the line.

  2. joel writes:

    Hi Noah- Thanks for the tip!

    Agreed about the brass issue, that’s a big concern for me. But I’m not sure how the ball-lock QD will attach to my (non-Corny) keg tap?

    Here’s a link to the Carbonator cap, and the ball-lock fitting too, from More Beer. Looks like a great solution, especially if you’re only using it for plastic bottles, or also with a corny keg.

  3. Alan S. Blue writes:

    I keep thinking it should be possible to skip the CO2 tank and regulator (the two priciest parts) and work from dry ice.

    You end up with more ad hoc pressure regulation, and you’d want to actually perform your carbonation on larger batches (or more bottles). But the price-per-bottle-carbonated should be reasonable if there’s dry ice to be had. (It’s $1/pound near me).

  4. Neil writes:

    Nice writeup! I have a similar system based on one over at Instructables.com, I use a tire valve stem on the bottle cap. I find that if I can get a 1 liter bottle with a wide mouth (the size used for the old 3 liter bottles) I can get ice cubes in more easily, and more CO2 dissolves in cold water.

  5. Alex writes:

    Why build this? Sodastream is a ready made machine that does just this.

  6. joel writes:

    Alex- If that’s how you feel then you’re in the wrong place 🙂

  7. Pencilneck writes:

    I just used a bottle cap with a 1/2″ hole drilled into it, then pulled an automotive tire valve stem though. Then I use a locking tire chuck on the end of the hose, so the bottle end of my arrangement cost me under $10. The valve stem caps never failed, I was pushing upwards of 80psi.

  8. whizbo writes:

    Have you tried carbonating fruit?

    It works best if you build a wide mouth water bottle rig similar to what you show above. That way it’s easy to get the fruit in and out.

  9. Ryan writes:

    This is amazing…how many liters of liquid can you carbonate using one 5lb tank of CO2?

  10. Roman writes:

    I just purchased a very similar setup, and I have the carbonater cap with ball-lock quick disconnect. It works, but not perfectly. There are two issues. One, I’d love to make a cap that would let a 1/4″ hose through it with a carbonation stone at the bottom. I think the carbonation would be much faster, with less shaking and finer bubbles. Second, is I hate that the water goes flat pretty quick after opening, unless you keep re-filling it with co2 after very glass. So I’ve seen some people make a tap for 2 and 3 liter bottles that allows to both carbonate and dispense from the bottle without having to open it. Man it’d be cool to combine those ideas. But at the very leas, can anyone here help me make a cap that would let the 1/4″ hose through so I can carbonate using the .5 micron diffusion stone?

  11. Mr. Fizz writes:

    You really should look at this video: http://www.youtube.com/watch?v=lRgfsa8zOio. Its a “How To” demo that really drives home the points you all make here (except for the dude that thinks everyone should buy SodaStreams). It’s pretty straightforward, really, and it demonstrates the quick ‘n easy use of cheap valve caps.

    In response to Ryan’s 4/21 question – beverage industry standard level of carbonation is 8g/L. 5# is 2268g. You can chop that up into 283 little 8-gram chunks & carbonat 283 one-liter bottles. Me, I like to serve my guests SUPERcarbonated beverages like this Coca Cola Classic: http://www.youtube.com/watch?v=nTWgOq6MHOs ‘cuz they’re more fun.

  12. Robby DeNicola writes:

    You guys are WRONG about using brass for CO2 beverages.

    The following is quoted from Page 1004 of Volume 1 of the ASM Metals Handbook Eighth Edition (3).

    “All copper alloys are deemed to be suitable under most conditions of use with dry carbon dioxide, moist carbon dioxide and carbonated beverages.”

  13. joel writes:

    Hi Robby- I think your handbook may be a bit dated… looks like the 8th edition of vol. 1 is from the 60s? In any case, a quick Google search turns up numerous sources & studies which link copper poisoning (from ingesting carbonated water that contacted brass or copper plumbing) to gastrointestinal illness.

  14. Mister Fizz writes:

    Actually, Joel, it has been known at the very least since the 1800’s that seltzer water reacts with copper to create copper carbonate. The poisonous effects of that substance has also been well understood for a long time. An article by R. Ogden Doremus, M.D. appeared in the NY Times on July 7, 1854 (reprinted from the American Medical Monthly) describing illness in some patients occurring shortly after drinking tainted soda water led to vomiting, colic, pains, etc. In St. Louis, some believed that consuming the poison led to the onset of cholera in patients predisposed to the disease. At the time, a number of copper pressure vessels were used in the city to house carbonated water. A copy of the old article has been posted courtesy of the NY Times here: http://query.nytimes.com/mem/archive-free/pdf?res=FA0B15F93859157493C5A9178CD85F408584F9

    The Old Croton Aqueduct brought water to the City of New York from the Croton River 41 miles away. The 5-year project ended in 1842. The small amount of naturally occuring dissolved co2 in that Croton water was known to act upon lead pipes causing lead to leach into the water being consumed by the Manhattan residents.

  15. Patricia Lutz writes:

    This is great! I’m currently in the process of acquiring all the pieces to build one myself (going to get the CO2 tank from a gas supplier today). The only variation is that I have the Carbonator Cap (as previous commenters have mentioned), which attaches to a ball-lock quick-disconnect. So far, I find it tricky to attach these two parts, so if anyone has any tips on that, I’d be happy to hear them.

    As for the SodaStream machine, I feel the 2 primary reasons for not getting one are: 1) you can only carbonate water (no juice, fruit, etc.); and 2) you must use SodaStream’s proprietary CO2 canisters because they have a “special” (i.e., not the standard CGA-320 valve) valve. So, they are limiting and more expensive. Plus, it’s a lot more fun and rewarding to assemble your own custom device!

    Lastly, in terms of the brass fittings, I understood that the issue was that brass fixtures contain trace amounts of lead, which is know to be a health hazard. Even the recent California Lead Free Law (effective January 1, 2010) allows for 0.25% lead content in plumbing fixtures.

    Happy carbonating!

  16. neil writes:

    I’ve seen setups like this all over the place, but I’m looking for cheaper yet!

    I found this rather silly gadget: http://www.thinkgeek.com/geektoys/science/c908/, which let’s you carbonate the really old fashioned way: vinegar and baking soda in one bottle and the liquid in the other. I got it to work just once. The problem isn’t the amount of pressure, there’s plenty of that. The problem is that the gadget itself is poorly made out of cheap plastic parts and leaks.

    Although I haven’t tried it, it should be possible to use a two ended version of this project (parts 5-10 at both ends of the hose) to create a better version of that device. This would save a bit of money on the tank, regulator, etc. Any suggestions?

    Anyone know how much pressure is needed to get the gas through one of those carbonator caps at MoreBeer?