The standard cylinder with 425 grams of CO2 carbonates about 60 litres. Where to swap it, what a swap costs, whether refilling is allowed and why cylinders from different brands usually fit.
In short
- 425 g of CO2 is enough for about 60 litres at medium fizz, and for 40 to 50 at strong fizz.
- Swapping in a shop: 7 to 10 euros per cylinder; buying new with a deposit: 25 to 35 euros.
- Almost all cylinders have the same thread, so swapping across brands is possible.
- Refilling it yourself is possible, but only with an adapter and food-grade CO2, never with fire extinguisher gas.
What is in the cylinder
A standard cylinder for soda makers holds 425 grams of food-grade carbon dioxide (E 290), liquid under about 60 bar of pressure. When you carbonate, it escapes as gas into the water. The figure “up to 60 litres” applies to medium fizz. If you like it strong, you get 40 to 50 litres; if you like it gentle, 70 to 80. There are also larger cylinders of 1.3 kilograms for about 180 litres, which only work with special machines or adapters.
Swapping in a shop
In Germany you hand in the empty cylinder for a full one and pay only for the filling: 7 to 10 euros, depending on the retailer and brand. Formally the cylinder itself belongs to the manufacturer, which is why it works like a deposit. The first time you buy, you pay 25 to 35 euros, of which 15 to 20 euros is the value of the cylinder. Swap points are supermarkets, drugstores, DIY stores and electrical retailers, many with swap machines at the entrance.
Does every cylinder fit every machine?
Most cylinders have a screw thread to the same standard, so cylinders from different brands fit each other. Some newer machines use a quick-release system (“Quick Connect”) that only works with matching cylinders. Adapters between the two systems start at 10 euros. When you swap, make sure you get the same system back.
Refilling it yourself
Possible, but with restrictions. You need a large food-grade CO2 bottle (about 6 or 10 kilograms, from a gas supplier or the drinks industry), a filling adapter with a scale and a bit of practice. The filling then costs about 1 to 2 euros per cylinder. Important: food-grade CO2 only, never gas from fire extinguishers or industrial bottles, and do not overfill (425 grams plus the empty weight stamped on the cylinder). Manufacturers exclude refilled third-party cylinders from the warranty, and cylinders have to be tested every ten years, which happens automatically when you swap in a shop. More on safety in the article Safety.
When is the cylinder empty?
When the fizzing gets quieter and the water stays flat despite several presses. A full cylinder weighs about 1.2 kilograms, an empty one about 0.75 (the empty weight is stamped on the cylinder). A kitchen scale tells you how much is left. What a litre finally costs is worked out by the soda maker cost calculator.
Frequently asked questions
Can I order cylinders by post?
Yes, mail-order retailers send full cylinders as dangerous goods in suitable packaging. Empty ones go back in the same box. Swapping in a shop is usually cheaper.
How long does an unused cylinder keep?
Practically indefinitely, the valve is sealed. Store it cool and upright, out of the sun.
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