Connect TR21-4 soda cylinder valve to CGA-320 CO2 cylinder valve
How to join TR21x4 (soda / SodaStream-style) and 0.825"-14 NGO RH, and what stops it leaking.
Not a direct fit. Joining TR21-4 soda cylinder valve to CGA-320 CO2 cylinder valve needs a TR21-4 to CGA-320 soda cylinder adapter.
The two ends
- End A
- TR21-4 soda cylinder valve (TR21x4 (soda / SodaStream-style))
- End B
- CGA-320 CO2 cylinder valve (0.825"-14 NGO RH)
- A seals on
- O-ring on the valve stem
- B seals on
- nylon or fibre washer inside the nut against the valve outlet
- Part needed
- TR21-4 to CGA-320 soda cylinder adapter
The part to buy
A small soda-maker cylinder ends in a TR21-4 trapezoidal valve, not a normal gas outlet. A TR21-4 to CGA-320 adapter presents a standard CGA-320 nut so a keg regulator can run off a repurposed soda cylinder.
Genuine SodaStream cylinders often add a proprietary valve on top of the TR21-4 thread and can need their own adapter, so a plain TR21-4 adapter may not fit every soda bottle. Check whether your cylinder is a standard TR21-4 or a SodaStream-locked one first.
Related connections
Sources: CO2Art guide to cylinder connections (CGA320, W21.8, DIN477, BS341, G5/8, TR21-4) ยท CGA-320 CO2 cylinder valve outlet thread reference (0.825in-14 NGO, RH)