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Connect W21.8 CO2 cylinder valve to G5/8 regulator inlet

How to join W21.8-14 (DIN 477 / BS 341 No.8) and G5/8 (BSP parallel), and what stops it leaking.

End AW21.8 CO2 cylinder valve (W21.8-14 (DIN 477 / BS 341 No.8))Needs an adapterEnd BG5/8 regulator inlet (G5/8 (BSP parallel))

Not a direct fit. Joining W21.8 CO2 cylinder valve to G5/8 regulator inlet needs a W21.8 to G5/8 regulator inlet adapter.

The two ends

End A
W21.8 CO2 cylinder valve (W21.8-14 (DIN 477 / BS 341 No.8))
End B
G5/8 regulator inlet (G5/8 (BSP parallel))
A seals on
captive O-ring or washer in the nut against the valve outlet
B seals on
flat washer on the face of the inlet
Part needed
W21.8 to G5/8 regulator inlet adapter

The part to buy

The European counterpart: a W21.8 to G5/8 adapter puts a G5/8-inlet regulator onto a W21.8 (DIN 477 / BS 341) CO2 cylinder. The W21.8 nut lands on the cylinder outlet and the G5/8 face seals to the regulator.

W21.8 is 22mm at 14 TPI and will not start on a CGA-320 tank, so confirm your cylinder is genuinely W21.8 before buying this adapter. Force never makes a cross-standard thread start; it just damages the outlet.

Related connections

W21.8 CO2 cylinder valveW21.8-14 (DIN 477 / BS 341 No.8)G5/8 regulator inletG5/8 (BSP parallel)CGA-320 CO2 cylinder valve to W21.8 CO2 cylinder valveadapterCGA-320 CO2 cylinder valve to G5/8 regulator inletadapterTR21-4 soda cylinder valve to W21.8 CO2 cylinder valveadapterCGA-580 nitrogen / beer-gas cylinder valve to W21.8 CO2 cylinder valvenot compatible

Sources: CO2Art guide to cylinder connections (CGA320, W21.8, DIN477, BS341, G5/8, TR21-4) ยท ISO 228-1 (G / BSP parallel pipe threads)