SodaStream adapter for a 2 kg CO2 cylinder: setup, fit and savings

A SodaStream adapter lets you run your sparkling water maker from a large refillable CO2 cylinder instead of the 425 g exchange cylinders. For the Terra, DUO and Art (the machines with the pink Quick Connect cylinder) you need a kit with a 1.5 m hose, a pressure gauge, a release valve and a Quick Connect plug, plus a 2 kg food-grade CO2 cylinder. One 2 kg filling makes about 280 litres of sparkling water, against about 60 litres from a 425 g cylinder. Below: which machines fit, what to buy, what a litre costs, how to set it up safely and how to get the cylinder refilled.

Which machines take a SodaStream adapter

SodaStream uses two cylinder systems, and the adapter has to match the machine, not the cylinder.

The Quick Connect machines are the simplest case. The plug at the end of the adapter hose goes into the slot where the original cylinder sits, so nothing on the machine is cut, drilled or modified. The hose then runs out of the back or side of the machine to the cylinder standing next to it.

For the screw-in machines (Classic, Source, Crystal and older models) you need an adapter for the TR21-4 thread. We do not list a TR21-4 adapter in the shop at the moment; it is available on request, so ask us before you order. Our accessories category shows the adapters that are in stock. Check which cylinder your machine takes first: the pink cylinder clicks in, the blue one screws in.

What you need: CO2 cylinder for SodaStream plus adapter kit

All Intergases refillable CO2 cylinders have the same valve outlet, W21.8 × 1/14″ (DIN 477 No. 6). That is the thread the adapter kit screws onto. You have three ways to put a setup together:

The 2 kg CO2 set with Terra/DUO/Art adapter is the same hardware as buying the two parts separately, for 4.99 € less (79.98 € − 74.99 € = 4.99 €).

The 2 kg cylinder is refillable steel, TÜV-approved, delivered filled with food-grade CO2 (E290), and it is yours: no rent and no deposit. It travels as an ordinary parcel, so it arrives like any other online order, on average within 2–5 business days across the EU.

The 615 g disposable set uses the M11×1 adapter kit, because disposable cylinders have an M11 × 1 thread instead of W21.8. It suits you if you want to try an external cylinder without committing to the larger size, or if space next to the machine is tight.

What a litre of sparkling water costs

The comparison rests on two figures: about 60 litres from a 425 g exchange cylinder (the figure SodaStream states for its cylinders) and about 280 litres from a 2 kg Intergases cylinder. 280 ÷ 60 = 4.7, so one 2 kg filling replaces roughly 4.7 exchange cylinders.

Exchange prices in German shops vary with the retailer and with promotions. In supermarket leaflets the regular price is often 7.99 € per 425 g cylinder, and promotions bring it down to about 4.50–7 €. The table rounds the regular price to 8 €.

In the first filling you pay for the hardware, so that litre is more expensive. The saving starts with the first refill: 4.7 exchanges cost 4.7 × 8.00 € = 37.60 €, a 2 kg refill costs 19.99 €, so each refill saves about 17.61 €. If you only ever buy exchange cylinders on promotion at 4.49 €, the same 4.7 exchanges cost 4.7 × 4.49 € = 21.10 €, and the refill saves only about 1 €.

A worked example for a household that empties two exchange cylinders a month: 24 cylinders × 60 L = 1,440 L a year, which costs 24 × 8.00 € = 192.00 €. The same water from 2 kg fillings: 1,440 ÷ 280 = 5.1, so about five fillings. Year one is the set plus four refills, 74.99 € + 4 × 19.99 € = 154.95 €. From year two it is five refills, 5 × 19.99 € = 99.95 €, roughly half the exchange cost. The refill price includes the prepaid return label for sending the empty cylinder back; any shipping charge shown at checkout is not included in these figures.

Setting up the SodaStream adapter in five steps

The kit is hand-tightened, but a wrench is recommended for the cylinder connection. Plan ten minutes for the first setup.

1. Connect the hose to the cylinder. With the cylinder valve closed, screw the adapter’s W21.8 nut onto the valve outlet. Tighten by hand, then a little further with a wrench. Do not force it.
2. Fit the plug into the machine. Remove the original cylinder from your Terra, DUO or Art and place the Quick Connect plug where the cylinder sat. Route the 1.5 m hose out of the machine without kinking it.
3. Stand the cylinder upright. CO2 is stored as a liquid; the cylinder must stand upright so that only gas reaches the hose. Secure it so it cannot tip over, for example against a wall or in a cupboard corner.
4. Open slowly and check for leaks. Open the cylinder valve slowly and read the pressure gauge. Brush soapy water on every joint: bubbles mean a leak. Close the valve, use the release valve to vent the hose, tighten the joint and test again.
5. Carbonate as usual. The machine works exactly as before. When you will not use it for a few days, close the cylinder valve.

Safety rules that apply to every CO2 cylinder:

• Never heat the cylinder, and keep it away from radiators, ovens and direct sun. Pressure rises with temperature.
• Keep the cylinder and hose away from the machine’s electronics and power cable.
• Close the valve and vent the hose with the release valve before you disconnect anything.
• Keep the room normally ventilated; CO2 is heavier than air and collects low down if a joint leaks.

If you want to know more about regulators, threads and gaskets in general, our guide to regulators and adapters covers them, and the updated gas accessories guide goes into the current kits.

When the cylinder is empty

The gauge on the adapter shows when pressure drops. You then have two routes to a full cylinder:

• Intergases parcel refill. Order the CO2 cylinder refill (19.99 € – 29.99 € for 2 kg and 3.75 kg cylinders). You get a prepaid return label, send the empty cylinder by parcel, and you get a filled cylinder back, safety-checked and filled with fresh food-grade CO2 at our own filling facility in Poland. If you bought the cylinder from us, you can choose exchange instead and receive a full cylinder of the same size; you need the order number of the original purchase.
• A local filling station. Many gas suppliers fill CO2 cylinders with a W21.8 valve. Ask for food-grade CO2 (E290); technical CO2 is not meant for drinks.

Any cylinder you refill must carry a valid test date. If you are weighing up refill against exchange or a new cylinder in more detail, read our comparison of refill, exchange or buy new.

FAQ

Is an external CO2 cylinder on a SodaStream safe, and does it void the warranty?

The setup is as safe as the original cylinder when the cylinder stands upright, the joints are leak-checked with soapy water and the cylinder is kept away from heat. Whether the warranty is affected depends on the manufacturer’s terms for your machine and country, so read those before you connect anything. The adapter does not modify the machine; it sits where the original cylinder sits and can be removed.

How many litres of sparkling water does a 2 kg CO2 cylinder make?

About 280 litres per filling. A 425 g exchange cylinder makes about 60 litres, so one 2 kg filling replaces roughly 4.7 of them. The exact figure depends on how strongly you carbonate.

Can I use the 3.75 kg CO2 cylinder with my SodaStream?

Yes. The 3.75 kg cylinder (119.99 €) has the same W21.8 valve and connects through the same adapter kit. It holds nearly twice the gas of the 2 kg cylinder; at the 2 kg rate that is about 280 × 3.75 ÷ 2 = 525 litres. It is taller and heavier, so check that you have room next to the machine.

How do I refill the 2 kg cylinder?

Order the CO2 cylinder refill, send the empty cylinder with the prepaid return label, and you get a filled cylinder of food-grade CO2 back. Alternatively, a local gas supplier with food-grade CO2 can fill it, provided the cylinder’s test date is valid.

Related products

• 2 kg CO2 set with Terra/DUO/Art adapter, 74.99 €
• 2 kg CO2 cylinder, 49.99 €
• W21.8 adapter kit for Terra, DUO and Art, 29.99 €
• M11×1 adapter kit for disposable cylinders, 29.99 €
• CO2 cylinder refill
• All CO2 cylinders