This is an update of a post I made over on Medium several years ago. All the numbers, maths and links have been updated and corrected where needed.

I am an unabashed soda-holic. So much so, my soda consumption was making a serious dent in my monthly food budget. Back in 2005, I was buying 12 pack cans of club soda at $3 a pack ($1.42 per litre), 2 litre bottles at $1.99 ($1 per litre) plus it all had a big carbon footprint with all the travel, storage, packaging and more involved in just getting carbonated water with a tiny bit of minerals in it.

In the mid 2000s, I discovered a company called Sodastream, part of the (now defunct) SodaClub mail order service (this was long before Sodastream showed up in Walmarts and London Drugs). When they first launched in Canada, it wasn’t actually too bad a system – they had both 120l CO₂ tanks and the now familiar paintball gun sized tanks you see on store shelves, and they delivered. I was a very early sign up for the service.

Even back then when the tanks and their refills were a lot better priced, it wasn’t cheap. I’ll detail the costs later on, but I worked it out that a typical litre of Sodastream soda water was $0.65/l in the first year, and $0.40/l in the second year onward. And the real problem with Sodastream is the very low amount of actual carbonation: the system is designed to max out at 20 psi carbonation levels. Most store bought club soda is around 45psi carbonated.

Then I discovered I could make my own soda, using a commercial 20 or 30lb CO₂ tank, a standard keg pressure regulator, a ball lock cap and hose system, and something called a carbonator cap. An initial $200 investment (about double the cost of a Sodastream initial setup), that would deliver me soda water at $0.12/l in the first year, and less than $0.02/l every year after that. And I’m going to tell you how to do the same exact thing.

Yes, you can get soda water made in the home for as little as 2 pennies per litre.

A Short Soda Water History

Why is carbonated water often called “soda water”?

Before the modern day efficient use of CO₂ gas in “charging” or infusing water to become carbonated, people could carbonate water by using sodium bicarbonate (baking soda) and some kind of acid (like citric acid); these two elements combined would release CO₂! This is why soda water took off as the descriptor.

There is a dark side to this as well. Back when people didn’t know that things like cocaine and radium were bad for you, some soda shops in the 1800s would use sulphuric acid and chalk instead of baking soda and citric acid to create bubbly water – dangerous stuff!

In this article, I really should be using “carbonated water” to describe what I’m writing about, but please excuse me if I call it soda water instead.

For decades now, bars and restaurants have offered soft drinks (sodas, pop, whatever you want to call it) in bulk by using two things – a canister full of concentrated syrups (from brand names like Coca Cola or Pepsi or Dr. Pepper), and pressurized tanks of carbon dioxide (CO₂). Complex systems introducing the CO₂ gas to ice cold water through a regulated feed tube, and that instantly created soda water would mix with preset amounts of the syrup to produce soft drinks on the fly, on demand.

These systems aren’t practical for home use, because of the expense of the equipment used, the space they took up, and the need to high-chill water on demand. Why chilled water? The colder water is, the better CO₂ incorporates and infuses into the water. If you try to carbonate room temperature water, it will contain less than half the carbonation that 3C water will.

Right up until the mid-late 1990s, this was your only option for instant water carbonation, if you wanted to use a bulk gas tank. And it wasn’t practical for most home use.

So right up through the mid-late 1990s, if you wanted soda water in the home, you had to rely on siphon bottles and CO₂ cartridges, or buy from the declining number of siphon bottle delivery services that existed up until that time.

Enter the Carbonator Cap

In the mid 1990s, a fellow patented an invention that would turn the home carbonating game on its head, as far as water is concerned. That patent is for the carbonator cap. It’s entire purpose was to turn commonly used CO₂ tank / regulator rigs used for beer serving (a much simpler system than soft drink delivery systems) into a carbonation system for water, using standard 2l PET bottles (those high pressure plastic bottles all soft drinks are sold in).

It’s taken a long time for this patented idea to become a product, but it started showing up in the late 1990s with limited production runs. Today, other similar devices have come out, including steel ones, but you can still buy the original Carbonator Cap. You can also build your own filling system using ball lock filling caps and tire inflation valves (though they can make everything smell like rubber).

The Rest of the Tools Needed

Besides the enabling star of the show — the carbonator cap — you need a CO₂ tank. The good news is, most home brew stores stock them and will “rent” them out to you for a big deposit (in Vancouver, you could get 20lb tanks for $100 deposits which is less than paying $200 for a new one).

In the USA, new 20lb tanks can be bought for as little as $90 USD, but in most cases, you’ll pay between $150 and $200 for a new tank and probably even more in Canada. And you have to have them tested and re-certified every five or more years.

You can use any size CO₂ tank though, and the good news is, 5lb CO₂ tanks, which will contain 44 cubic feet of CO₂ gas (by comparison a standard sodastream canister holds 8 cubic feet of CO₂) can cost as little as $55 to buy new, and are very cheap to refill ($20 or less).

Next up, you need a draft keg pressure regulator (usually under $60) and a line and ball lock filling cap (usually under $15). That is all you need to start making soda at home, at any strength of bubbles you want.

All the prices above are for new; you should be able to find these things on your local Craigslist or Facebook Marketplace for even less.

There is one more thing you need: empty PET bottles. You know, those standard 500ml, 1l and 2l soda plastic bottles. You can refill these things hundreds of times, safely.

You should be able to find most of these things at any home-brew beer store as well. And of course, you also need some some empty PET soda bottles, 500ml to 2l in sizes.

I have this system, based around a 30lb tank. My initial investment was about $150 ($190 Cdn dollars), plus a $30 payment for the first tank of gas (though I will get $100 CAD back once I return the tank and not get another refill – as if that will happen lol!). That 30lb tank lasts me at least one full year, even when making up to 6l of soda per day (my current average is 2.5 2l PET bottles consumed a day).

Let’s Look at the Math

Before I even get into the math, let me state the prices I paid for all the parts I’ve got in my home soda making kit, because while I’m not going to be using these numbers for the Keg System pricing below, I wanted to show you can even be cheaper than the prices I’ll outline way down this page. Here goes:

• 20lb CO₂ tank: $100 deposit, which included a full tank (normally you would pay up to $200 for the tank, plus $45 for filling).
• Dual Valve Keg Regulator, $48
• Line and Ball Lock: $12
• Carbonation Cap: $22 (it was more expensive back then)
• 4 2l PET bottles (in the form of 2l bottles of soda water): $4 (bought on sale, full!)

Total initial investment of $186, including a full tank of gas, as they say. This is my first year costs on the setup.

Now let’s look at the current ways to get soda water into your home and how much they cost. I provide a percentage comparison to the home 20lb CO₂ tank system as well. We base it all on consuming 4 litres of fizzy water a day (or two 2l PET bottles worth), which a normal family of four would easily consume daily.

Buying Pre-made Club Soda

A 2 litre bottle of club soda in Victoria, BC costs on average $1.50 for a no name brand. Sometimes cheaper, sometimes more expensive. The CO₂ pressure is around 40PSI, making it fairly fizzy but not like European fizzy (which is ultra fizzy). The per litre cost is $0.75 and your four litre daily consumption will cost you $3 per day not including bottle deposit, or almost $1,100 a year.

This is 2345% higher than the Home Keg system mentioned below.

If you buy club soda in the cans, here, typically a 12 pack of 355ml cans of club soda will cost you $3.99 on sale, and $4.99 regular price, so I’m going with $4.50 a twelve pack. The per litre cost is $0.95 and your 4 litres a day will cost you $3.80, not including can deposit. Yearly that is $1,387.

This is a 2982% increase over the home keg system.

Using SodaStream

First, I do not recommend Sodastream. Massive carbon footprint, very high consumables cost, and very expensive per litre costs. Plus the company owes me over $300, which I won’t get into here (happened when they transitioned over from Sodaclub to their new multinational brand and wouldn’t refund my tank deposits).

Also, Sodastream doesn’t carbonate nearly as strong as the home system does, it doesn’t even carbonate as strongly as store bought bottles of club soda, or home siphon bottles using CO₂ cartridges. A Sodastream system maxes out at 20psi pressure, but if you go by their “3 squirts” recommendation for a 1l bottle, it’s even less than that – around 15psi. That’s barely fizzy.

Currently in Canada, Sodastream systems cost from $100 to $160 or more, not including taxes. That gets you the machine, one paintball gun sized 14.5oz (not even 1 pound!) CO₂ tank and one bottles. You’ll need more bottles so that will run you another $20 for a few of them. You also definitely need to have at least two of their 14.5oz tanks – one running while the other you’re taking back to a store (hence bigger carbon footprint) to exchange. New full tanks are $40. We’re establishing the start up costs for Sodastream at $200 (which includes a basic model, extra bottles, extra tank, and taxes).

Sodastream likes to call their tanks “60l tanks” indicating it does 60l of soda. That’s straight out bullshit. Even if you do their recommended “3 squirts” you’ll be lucky to get 50l. If you want the max carbonation (20psi), you’ll be hard pressed to get 40 litres. We’ll settle on it being 50 litres per tank for low-level fizz.

Exchanging tanks is how you do this. In Canada, most places charge at least $20 for an exchange Sodastream tank (you leave the empty one). I’ve seen it as high as $30, and I believe more recently, there’s some kind of special environment tax on it as well. I’ve settled in on a price of $22.50 for the refill price. $22.50 to get you 50 litres of tepid, not too fizzy soda water.

With all that in mind, your first year costs for a Sodastream, getting 4 litres a day (1,460 litres a year), amortizing your initial equipment investment is a whopping $812.50 ($0.56/l) if you want the sad slightly fizzy water, and if you want the full 20psi soda water, it’s $995 ($0.68/l)! That’s right, one year of still under-carbonated water with a massive carbon footprint costs you $995 with a Sodastream system in the first year. And in year two? $670 ($0.46/l) for the sad fizzy water, and $821 ($0.56/l) if you want the slightly less sad 20psi fizzy water!

That’s right: even after you’ve amortized and covered the initial setup costs for your Sodastream system in the first year, in the second year, you’ll be paying as much as $1.12 for 2 litres of soda from your countertop soda maker.

This is a 1741% increase in cost over the Home Keg system detailed below.

I mean, holy crap. And I only barely touched on the carbon footprint. It’s massive with the Sodastream “system”. All these CO₂ tanks transporting back and forth! You transporting back and forth! It’s worse than buying the PET bottles!

Seriously, Sodastream is the Nespresso of the soft drink world. Stop using and supporting it!

Using Siphon Bottles

I love siphon bottles. I have a small collection of them, including some vintage ones from the 1930s that still work great. But they have three big problems. First they can provide even less carbonation than SodaStream does. Second, the cartridges used aren’t cheap. Even if you buy CO₂ cartridges (needed for the siphon to do its thing) in bulk, you can get them for about $0.35 per. but you’ll have to buy over 500 of them to get anything near this price.

Third, there’s a lot of waste to deal with: all that metal in the one-time use cartridges; if you can find a place to recycle them, it’s a pain to collect and transport them. Also, siphon bottles typically can hold up to a litre of cold water, but again, if you carbonate a full litre with just one cartridge, it will be extremely weak carbonation, on par with the “3 squirts” thing from the Sodastream; so as a result, I was only carbonating about 750ml of water.

I’ve done the math, and without boring you with the detailed breakdown, a siphon bottle system in the first year will cost you $820 to do 4 litres a day (1460 total litres, $0.56/l), and in year two, will cost $760 for the same volume ($0.52/l), all for the same level of carbonation as the “3 squirts” from the Sodastream. What’s ironic is, it’s still cheaper by the litre than the Sodastream!

Using siphon bottles is 1590% higher in price annually than the home keg system.

Using a Home Keg CO₂ system

Back up several paragraphs I showed how my own initial investment in equipment for doing this setup was $186. I’m going to be generous to the competition and say the initial setup cost is $250. For that $250, you get a filled 20lb CO₂ tank, a regulator, the line and ball capping system, the carbonator cap, and 4 starting 2 litre PET bottles.

That’s it, your cost for the first year is $250. Because a 20lb tank will take a year to do 4l of carbonation a day. In fact, it should do 1,800 litres easily before needing to be refilled. And that’s not at the paltry 15psi “three squirts” level Sodastream recommends. It’s not even at the maxed out 20psi level Sodastream can reach. Nor is it at the 40-45psi levels store-bought club soda has in PET bottles.

I’m talking 60psi, shave the hair off your tongue, bristle up your neck hair levels of carbonation.

In year two? That same level of carbonation, doing over 1,800 litres of soda water? Your cost is $45, plus one trip to the refill place (usually a fire-extinguisher refill service). And $45 is high (it’s what I pay in Victoria – in Vancouver, I was paying $32.

In year, one, doing not 1460 litres of soda water, but a whopping 1,800 litres, your cost per litre is $0.14.

In year two, doing another 1,800 litres over the course of the year, your cost per litre drops to $0.025. 2.5 pennies per litre. And it’s triple fizzy stuff, with the lowest carbon footprint of all methods of getting fizzy soda water in the home!

TL:DR

The above too much maths? Here’s the short and sweet in year two and beyond of ownership of these systems:

• Home Keg 20lb CO₂ tank Soda Water: 1,800 litres for $45, $0.025 per litre cost.
• Sodastream, yearly cost for 1,460 litres: $821, $0.56 per litre, 1741% higher than Home Keg System
• Buying cans of club soda yearly cost for 1,460 litres: $1,387, $0.95 per litre, 2982% higher than Home Keg System
• Siphon Bottle, yearly cost for 1,460 litres, $760, $0.52 per litre, 1590% higher than Home Keg System.

Now that I’ve convinced you a home keg system is the way to go, for the environment, for cost savings, and for making the hair on the back of your neck stick up from the amount of fizz in the water, let’s get into how to actually do it!

Becoming a Home Carbonated Water Manufacturer

So you bought, or leased, or borrowed a nice CO₂ tank. It could be a mega-sized paintball gun tank (some people claim they can get the tanks refilled for free at paintball gun places!), a 5lb, 10lb, 20lb or even a 30lb tank.

Full, these tanks can hold CO₂ at 850PSI or even higher. Because your PET bottle would explode anywhere near that pressure, you also bought a keg system regulator for the tank and have it sucurely attached to the tank. The purpose of the regulator is to take a gas, stored at a crazy high pressure (850psi) and let you deliver the gas at a lower pressure you set mechanically on the regulator. Regulators also have safety features built in so nothing explodes.

If you want grocery store levels of fizzy soda water, set the regulator at 45psi. If you want Euro-strength, set your hair bristling levels of fizz, set it as high as 60psi on the regulator. Your manual should explain how to adjust the regulator (its usually a flathead screw up front, or a dial with a plus and minus on it).

On the output end of the regulator assembly, you’ve attached the pressure line with it’s pre-connected ball lock valve securely to the regulator output using a screw tight bracket. So your setup looks like a tank with some gauges up top, and a stiff reinforced plastic hose coming from the thing with gauges, having a plastic knobby thing on the end of it.

And you have your trusty carbonator cap, which makes this all possible.

So how do you get soda water?

First, you fill a 2l PET plastic bottle with water, leaving about 7–8cm of headspace (just fill water until the bottle starts curving towards its top). Why the headspace? You need to have enough surface space for the CO₂ to saturate into your water. Next, make sure the bottles are chilled. We leave at least 2 filled bottles in the fridge overnight to get to around 3C (35–38F).

Once you’re ready with cold water in your PET bottles, here’s the next steps:

1. take the bottle, attach the carbonator cap to the bottle, squeezing out all the air in the PET bottle before making the cap air tight.
2. Check your CO₂ rig, you want the regulator to be set at around 35–60psi (depending how strong you want the fizz — start at 35psi and adjust after sampling your beverage).
3. Make sure your CO₂’s tank main valve is off, and your safety release lever on the regulator is in the off position
4. Attach the ball lock cap to the carbonator cap. Some residual CO₂ will make its way into the bottle, but it won’t be full, or pressurized yet.
5. Unscrew the tank’s main pressure valve to open the flow of pressurized gas, then slowly move the regulator’s safety release lever to the on position to fill and pressurize your PET bottle of water (key word: slowly).
6. Once the PET bottle is filled with pressurized CO₂, start shaking the bottle rapidly. CO₂ will only dissolve into water that the gas is actually touching; if you don’t shake the bottle, it will take an hour to fully dissolve into water; shaking rapidly will constantly expose new water to the CO₂ “gas”, speeding up the CO₂’s incorporation into the H20.
7. Shake the bottle for about 20–30 seconds. If you listen carefully, at some point, you’ll stop hearing the “hiss” of the pressurized CO₂ moving from the tank to the PET bottle — at this point, your water is nearly fully saturated with all the CO₂ it can handle — but not quite. There’s still some oxygen and other elements of “air” in there.
8. Optionally, you can do a second CO₂ introduction; flip the regulator valve’s safety latch to off, and remove the ball cap from the carbonator cap on your bottle. Slowly unscrew the carbonator cap, and you’ll release all the pressure in the PET bottle (careful, it will bubble up and can spray you if you do it too fast). Let the bubbles settle for 10 seconds, then put the Carbonator cap back on, squeezing the bottle again to remove all (most) of the air inside as you tighten it. The bottle will continue to fill with gas (CO₂ at this point) once the cap is on securely. Reattach the ball lock cap from your tank, and flip the safety lever on the regulator back to “on” to re-pressurize the PET bottle. Shake like crazy again for 5–10 seconds. All of this optional secondary amount will remove remaining oxygen etc from the bottle and just keep it a full H₂O/CO₂ environment, making the water even more fizzy.

I don’t really do step 8 any longer. It doesn’t make that much a difference to the final fizz. And besides, leaving the filled PET bottle, uncapped, in the fridge before turning it into soda water helps evacuate residual oxygen anyways. But there you go — that’s the full steps to making soda water at home from a commercial CO₂ tank.

Here’s a video of the process.

Some Considerations

PET Bottles are built to withstand well over 125psi (failure rate is rated at 150psi), and they are a wonder of modern engineering, but they do not last forever. Count on replacing yours every 250–500 uses. (sidenote: isn’t it amazing this product people normally use once and dispose of / recycle has such a long lifespan of usefulness?) You can prolong the life of your PET bottles by controlling how fast you pressurize them: don’t just jam the regulator’s safety lever open, but slowly do it. Ditto with releasing pressure. I’ve used bottles for as long as 500 refills, but I get a bit nervous by that point. The super safe will replace bottles every six months or so (but I’ve heard of people using the same PET bottles for years). If they fail, the worst that can happen is you’ll get a high pressurized soak of ice cold water.

Tanks are big and ugly, so keeping one in the middle of your kitchen might turn off some people. You should keep it in a cool, dark place, never in sunlight. We keep it next to a credenza in our dining room, in a shady corner. It can’t be seen from most angles in the dining room.

Make sure your regulator is 100% working and attached – you are dealing with something with incredibly high pressure (the CO₂ tank holds the gas at up to 900psi!!! and this can be explosive). If you’ve never done this before, find a friendly, hands on beer brewing place and ask them to show you the ropes, set up your tank properly, and check the connections and fittings. That in mind, all my advice above and below is at you own risk.

Keep your main tank valve off when not filling your PET bottles. This serves two purposes: first it’s an extra safety precaution to keep your CO₂ tank safe and sealed, and second, it prevents any gas leaks through the regulator system when you’re not filling bottles. Even the best regulators can lead a bit of gas (think a dripping faucet effect); a slight leak could empty your tank over a period of weeks.

It’s not just for water! That’s right, you can carbonate almost any liquid with your new system. Just keep this in mind: sugar = foam and bubbles = a huge mess. You can avoid huge bubbles and a mess by being patient – do the carbonating thing (including shaking the bottle), but then set it aside for up to 10 minutes or more. When you go to finally unscrew the carbonator cap, do it slowly and methodically in stages. I’ve carbonated wine, re-carbonated beer (awesome use btw, if you buy beer in growler bottles!), even carbonated mixed cocktails like negronis (mmmmm tasty!).

Conclusion

And there you have it. My longest blog post, like, ever, and it’s so long, I am shaving off the end of it and putting that bit up as an accessory post to it. The topic is “become your own fancy mineral water manufacturer!”, and that will be coming soon!