DIY Carbonated Water Rig: Is All CO2 Created Equal?
January 13, 2021 2:34 PM   Subscribe

I hate Sodastream for various reasons, but I love fizzy water for all the regular reasons, so I'm thinking of making my own home carbonation rig. If I get a tank of CO2 from a welder's supply store or any other industrial source, will it be safe for consumption?

I'm looking into some kind of setup like the example at this link.

I assume the Popular Science website wouldn't just tell someone to go buy a bunch of poison CO2, I mean hell, their masthead lists an actual lawyer who would presumably tell them not to. But various other DIY pages caution that industrial CO2 "might" be toxic and you should just ask whether it's safe for human consumption. I assume an atom is an atom is an atom, but maybe the tank could be toxic or something?

Anyone have thoughts/knowledge on this?
posted by kensington314 to Food & Drink (13 answers total) 20 users marked this as a favorite
I occasionally need to buy dry ice. The same place that supplies the dry ice also sells CO2 tanks that are explicitly aimed at soda fountains. I believe that you have to pay for the actual tank the first time you get it. But after that, you can just exchange the empty tank for another full tank (though you still have to pay a fee for the actual CO2 inside it).
posted by JD Sockinger at 2:48 PM on January 13, 2021 [2 favorites]

Best answer: I get my CO2 from a welding supply company. I told them it was for home brewing and made sure it had an eductor tube and haven't had any issues. I don't think it has killed me yet.
posted by cmm at 2:49 PM on January 13, 2021 [3 favorites]

While there is technically a difference between "industrial grade" (99.5%) and "food grade" (99.9%) all of the N. American suppliers I've ever used (Airgas, AirLiquide, etc.) simply produce "food grade" and then sell that to industrial users rather than deal with the hassle of a separate supply chain for lower-profit gas.

...I mean, they'll still sell me Electronic Grade 1 (99.995%) for large dollars, but the baseline ends up being 99.9% and then things go up from there. For example, the lowest grade Airgas supplies is "bone dry" which is 99.9%.

However, if you want to be sure, just ask for the purity -- they should know (I mean, unless it's Bob's Random Gases or something).
posted by aramaic at 2:50 PM on January 13, 2021 [6 favorites]

(I should also mention that the purity percentages aren't the only things some folks care about -- when gas people say "contaminants" they mostly mean things like how much H2O, or how much O2 is allowed. If you need anaerobic gas, you want O2 to be below 10ppm, for example. For semiconductor uses, might want halocarbons to be held at or below 1ppb, with C1-C6 hydrocarbons less than 0.5ppm and so on and on. Any CO2 you'll get in N. America should be purer than the FDA requires unless something criminal is going on or you're buying some weird-ass import from god knows where.)
posted by aramaic at 3:12 PM on January 13, 2021 [1 favorite]

Best answer: If you wanna go down the rabbit hole of home carbonation, you gotta at least give a dive into Dave Arnold’s work:

Firm agree with folks that most gas is food grade, but it should at least be mentioned that the brass in food safe fittings is lead free. The brass in most non food grade fittings contains (minimal level of) lead, which is what marks it as not suitable for food grade status. But, really, this isn’t a problem because gas doesn’t leach the lead out of the metal in this application. Liquids can, but those don’t really interact with lead bits in a diy co2 system.
posted by furnace.heart at 4:07 PM on January 13, 2021 [1 favorite]

The New York Times had a step by step on how to build one, about a month ago.
posted by kestrel251 at 4:56 PM on January 13, 2021

A common concern I've read about, similar to filling SCUBA tanks with air, is ensuring that the air and machinery going into the tanks is clean. But if you're getting tanks from a reputable source then I wouldn't worry - it's the person who has a compressor behind their garage that I'd be worried about. And for CO2, it's unlikely someone has the equipment behind their garage :)
posted by jpeacock at 5:20 PM on January 13, 2021 [1 favorite]

Best answer: I get my kegerator CO2 from a welding supply place. Been doing it for years and I'm still alive. As far as I know, there's no difference between beverage CO2 and welding CO2 (and paintball CO2 etc.). The only thing I know is different is nitrous oxide; they put some sort of bitterant in the nitrous that you buy for automotive use, so you can't have any fun with it (jerks).
posted by Kadin2048 at 5:28 PM on January 13, 2021

The components I use, with Amazon links (yeah, I know, we're trying to cut Amazon out of our lives too, but I had the blog entry to cut and paste): And, of course, I use 1.5L carbonated water bottles. Chill the water first. About a hundred shakes (determined by closing the valve at the canister, shaking, watching for the secondary pressure to not drop; that seems to occur after about 80 shakes, the extra 20 are for good luck). You don't need the internal tube and the stone, but it seems to make it take fewer shakes (office-mate did a similar setup without the stone).

And, yeah, I went to my local welding/carbonation/oxygen supply place, told 'em what I was doing, and they sold me a canister that I swap out for refills. It's the same canisters they sell for soda fountains. I think I've got a 10lb container. Careful not to drop it/knock it over on the regulator, my primary gauge is all beat up now and doesn't register. I should take it apart and see if I can un-bend the internals. But it still carbonates.
posted by straw at 7:45 PM on January 13, 2021

Officially speaking, FDA's requirement for "food-grade CO2 is 99.9 % pure", whereas regular industrial CO2 is only required to be 99% pure CO2. Food-grade simply means "safe to come into contact with food" (no cross-contamination). Food-grade transportation is kept cleaner. Industrial grade has no such restrictions.

Please keep in mind there's also "medical-grade" and "beverage-grade".

Officially, restaurants use beverage-grade CO2, which is the same grade used in breweries and soft drink makers.

You may want to read this seriouseats link:
posted by kschang at 9:25 PM on January 13, 2021

The Serious Eats page is good. One minor nit:
Before charging the bottle, squeeze out as much air from the headspace as possible. Air competes with carbon dioxide for room in water.
Yes it does, but the easiest way to deal with that is just to blow a quick phoof of CO2 into the carbonating bottle with the carbonating cap loose, then tighten it down and carbonate properly. You can run quite a large headspace inside the carbonation chamber without any risk of creasing the walls this way.
posted by flabdablet at 10:01 PM on January 13, 2021 [1 favorite]

Those creases seriously weaken the bottles, which are otherwise ridiculously strong.

I've reused creased bottles for a few years, so it's not the worst... But every bottle that has failed did so along a crease line from that same move.
(Note that this totals 2 bottles over about a decade)
posted by Acari at 6:57 AM on January 14, 2021 [1 favorite]

Best answer: I've been homebrewing for more than 20 years, and working from a home keg system for the last 13. I actually mostly stopped homebrewing a while ago, and mostly just use my kegs for carbonated water and cold brew coffee, with the occasional hard cider I've fermented.

I've never bought CO2 from anywhere but a welding supply shop, and have never had a problem. I've literally gone through hundreds of kegs off those tanks, and I can still type this and post it to Metafilter.
posted by rocketman at 9:26 AM on January 14, 2021 [1 favorite]

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