Converting a Threaded SodaStream/Drinkmate to a 5 lb CO2 Tank

Swapping the tiny 14.5 oz cylinder that ships with a threaded (screw-in) SodaStream or Drinkmate for an external 5 lb tank — same carbonation, without buying $15–20 exchange cylinders every 60 liters.

This only applies to screw-in machines. The connection depends on the TR21-4 thread — the “blue label” screw-in cylinder standard shared by classic SodaStream machines and Drinkmate. SodaStream Terra and Art use a push-in quick-connect cylinder and are not compatible with this approach — they need a different adapter, if one exists at all. Confirm your machine actually screws the cylinder in before buying anything.

The core idea: no regulator

The stock 14.5 oz cylinder feeds the machine unregulated, at something like 850 psi (CO2 tank pressure is a function of temperature, not fill level, until the tank runs dry — so a “full” 5 lb tank and an almost-empty one both sit around the same pressure at a given room temperature). The machine’s own trigger valve is what meters gas into the bottle in short bursts; it’s designed for that pressure already.

That means the standard approach is a direct adapter hose — CGA320 (the tank’s valve standard) on one end, TR21-4 (the machine’s cylinder thread) on the other — with no separate pressure regulator in between. Adding a regulator dialed down to, say, 130 psi would just give weaker carbonation than stock, not a safety improvement; the machine already expects full cylinder pressure.

Parts

• 5 lb aluminum CO2 cylinder, CGA320 valve. Aluminum over steel — lighter, won’t rust internally. Buy new, not refurbished, DOT-approved with a current hydro-test date (5 lb aluminum cylinders in the US are DOT-3AL, hydro-tested every 5 years; the date’s stamped on the collar and a gas supplier will check it before filling or exchanging). VEVOR and Beverage Elements both make commonly-recommended 5 lb aluminum CGA320 cylinders.
• CGA320 → TR21-4 direct adapter hose, 36–60 in, braided stainless or reinforced food-grade hose, rated well above tank pressure (most listings claim 4500–5000+ psi, which is the hose/fitting rating, not an indication you need that much pressure). Get one with a gauge and bleed valve — the bleed valve lets you depressurize the line before disconnecting, which matters (see below). Grab spare nylon washers/o-rings while you’re at it.
• Tank strap or wall bracket. A pressurized 5 lb cylinder becomes a genuine projectile hazard if the valve gets sheared off in a fall — secure it upright, always. Upright also isn’t optional for a different reason: these adapters pass gaseous CO2 only. A tipped tank can send liquid CO2 into the machine, which the setup isn’t built for.

Tools/consumables: adjustable wrench, a spray bottle of soapy water for leak-checking every threaded joint, spare washers.

Where to buy

Cylinder — buy local if you can. A welding or beverage-gas supplier will sell a 5 lb aluminum cylinder and fill it on the spot with beverage-grade CO2, and you skip shipping a pressure vessel entirely. If ordering online, the VEVOR 5 lb aluminum CGA320 cylinder is the commonly-recommended budget option; homebrew retailers like MoreBeer and Williams Brewing carry better-vetted tanks and are reputable for this whole category.

Adapter hose:

Other reputable non-Amazon sources for the hardware in general: MoreBeer, Williams Brewing, Soda Dispenser Depot, or a local welding/gas supply shop for the tank itself.

Gas purity

An in-line filter is not the real control here, and a cheap one won’t reliably catch what actually matters: industrial and welding-grade CO2 can carry compressor oil and hydrocarbon residue that a basic filter doesn’t remove. Two things that do the real work:

1. Specify beverage-grade / food-grade CO2 at the fill counter, every time — not the general-purpose industrial tank.
2. Buy a new cylinder, so you’re not inheriting rust or residue from whatever the tank held in a past life.

An activated-carbon in-line gas filter from a homebrew supplier is a reasonable belt-and-suspenders addition, but largely redundant if the gas source is clean — and check its pressure rating before adding it to this unregulated, full-tank-pressure line, since most are speced for regulated low-pressure use downstream of a proper regulator.

Safety notes

• The cylinder is the real hazard, not the gas connection. Standing, strapped, away from heat and direct sun. A cylinder is not a countertop decoration — treat it like the pressure vessel it is.
• CO2 displaces oxygen. It’s heavier than air and pools low in a room. This is a real risk for any large-volume leak, not just a slow one — don’t store or operate the tank in a small closed cabinet with no airflow, and if you ever smell/hear a active leak, ventilate before troubleshooting.
• Bleed the line before disconnecting. The gauge/bleed-valve hose exists specifically for this — open it to vent residual line pressure before you unscrew anything, rather than cracking a pressurized fitting open by hand.
• Leak-test every threaded joint with soapy water after assembly — bubbles mean it’s not sealed.
• Don’t overtighten the TR21-4 end. The washer does the sealing, not torque.
• Drinkmate’s own warranty generally doesn’t cover damage from third-party CO2 sources — know that going in.

Before you order

• Confirmed the machine is screw-in (TR21-4), not the push-in quick-connect used on SodaStream Terra/Art
• Cylinder ordered/sourced: new, aluminum, CGA320, current hydro-test date, filled with beverage-grade CO2
• Adapter hose ordered: CGA320 → TR21-4, with gauge and bleed valve if available
• Tank strap or bracket sourced and installed before the tank goes anywhere near the counter
• Every joint leak-tested with soapy water on first hookup