Connect TR21-4 soda cylinder valve to W21.8 CO2 cylinder valve
How to join TR21x4 (soda / SodaStream-style) and W21.8-14 (DIN 477 / BS 341 No.8), and what stops it leaking.
Not a direct fit. Joining TR21-4 soda cylinder valve to W21.8 CO2 cylinder valve needs a TR21-4 to W21.8 soda cylinder adapter.
The two ends
- End A
- TR21-4 soda cylinder valve (TR21x4 (soda / SodaStream-style))
- End B
- W21.8 CO2 cylinder valve (W21.8-14 (DIN 477 / BS 341 No.8))
- A seals on
- O-ring on the valve stem
- B seals on
- captive O-ring or washer in the nut against the valve outlet
- Part needed
- TR21-4 to W21.8 soda cylinder adapter
The part to buy
The European version: a TR21-4 to W21.8 adapter takes a soda-maker CO2 cylinder onto a W21.8-inlet regulator. It converts the small trapezoidal soda valve to the standard European cylinder connection.
As with the CGA-320 version, a SodaStream-specific valve can sit on top of the TR21-4 thread and defeat a plain adapter. Confirm the cylinder is standard TR21-4 before buying, and never leave a small soda cylinder pressurising a regulator unattended.
Related connections
Sources: CO2Art guide to cylinder connections (CGA320, W21.8, DIN477, BS341, G5/8, TR21-4)