Having used a Sodastream for a few years now, one of my main gripes was the need to swap out the gas canisters every month or two, which involved swapping at a store for what seemed like a fairly high cost.

To address this, I thought I’d go ahead and buy a bigger general food-safe CO2 tank.

Purchasing & Economics

The nearest place I could find, being in East Hampshire, was a place in Aldershot called “Rent Free Gas”. The guy there was super helpful. Technically the bottle stays under their ownership (seems to be the standard for gas tanks, at least here in the UK), so they helped me set up an account with them, and let me see the different sizes available.

I landed on a tank providing 3.15kg of CO2, which was on the smaller end of what they had in stock. I would have liked to get more, but this size of tank is already 10kg overall, and this is something I need to store in my flat.

There’s a refundable deposit for the bottle of £55, with the CO2 itself costing £31.26 for the entire 3.15kg (inc. VAT). This totalled £86.26 for this first trip, but future refills will just be the gas cost. For comparison, a standard Sodastream bottle contains just 425g of CO2, and that was costing £15 each time (when swapped for an existing bottle). Normalising those values:

• Sodastream bottle: £3.52/100g
• Big bottle (including deposit cost): £2.74/100g
• Big bottle (just the gas): £0.99/100g

So it’s cheaper even if you consider the bottle deposit as a loss, and then refills are way way cheaper. Definitely seems worth doing. While I have to travel a little further than normal for the big bottle, it should be equivalent to ~7.4 standard Sodastream bottles, so probably less overall travelling and time spent at the shops.

There was another one-off cost though, which was £10 for the adapter used as per the setup below.

The Setup

Warning: The following may be unsafe. This should not be considered expert information or guidance at all. Use this information at your own risk, and handle pressurised gas with care.

For actual use with my Sodastream, I landed on a setup where I simply refill the existing two official bottles I had, and use those in my Sodastream like normal. There are options to connect larger bottles directly to a Sodastream, but using the original bottles feels a little safer to me, while keeping the fill station placement more portable and not tied to where I’m storing the large bottle.

There are various bottle-to-bottle adapters available, but I went with a fairly basic straight adapter:

Looking at the original eBay listing I ordered from, it depicts a much better finished fitting with a silver thumbscrew and better markings, so I think I ended up with a cheap imitation of a better product. It seems to work though. Don’t get a basic thread adapter without a valve; you need a way to controllably release pressure in the adapter itself to avoid any bottles being launched!

Here’s the setup in use:

Before I plan to re-fill, I freeze the empty Sodastream bottle. This eases being able to back-fill more gas into the Sodastream bottle by keeping it in a more liquid state rather than an expanded gas state, especially as the Sodastream bottle will be getting naturally heated by the compression of gas into the bottle during the filling process.

I have a towel to handle the frozen Sodastream bottle, and to handle the release valve (to lower the risk of my fingers being frozen by compressed CO2!).

The process generally is:

• Weigh the Sodastream bottle to get a known empty weight.
• Screw the adapter onto the large bottle, then the Sodastream bottle into the other end of the adapter.
• Ensure the relief valve (adapter thumbscrew) is closed.
• Very, very slowly open the valve of the large bottle until you hear it filling with a screeching noise.
  • There seems to be a knack to this, in terms of speed and how much you open it. Going too fast causes the Sodastream bottle valve to close up, in which case you have to release the pressure and start again.
• After a while, close the large bottle valve.
• Open up the relief valve on the adapter (using gloves or a towel). I find this lets a little pressure out but then the o-ring inside freezes, so you have to then unscrew it a fair bit more to actually release the held pressure.
• Then unscrew the Sodastream bottle from the adapter.
• Weigh the Sodastream bottle again to check fill amount.

I’m not sure if there’s danger in over-filling the Sodastream bottle, or if the pressure between the two bottles equalises out at safe levels. So far I’ve just been cautious and trying to learn the process, stopping early to check the fill amount. In my two re-fills so far I’ve only filled the Sodastream bottles by about 110g or so, which is about a quarter of their capacity, which I plan to improve upon and increase fill amounts but I’m just being overly cautious so far.