Connect CGA-320 CO2 cylinder valve to 1/4" NPT

How to join 0.825"-14 NGO RH and 1/4-18 NPT, and what stops it leaking.

End ACGA-320 CO2 cylinder valve (0.825"-14 NGO RH)Needs an adapterEnd B1/4" NPT (1/4-18 NPT)

Not a direct fit. Joining CGA-320 CO2 cylinder valve to 1/4" NPT needs a CGA-320 inlet stem with a 1/4 male NPT tail.

The two ends

End A: CGA-320 CO2 cylinder valve (0.825"-14 NGO RH)
End B: 1/4" NPT (1/4-18 NPT)
A seals on: nylon or fibre washer inside the nut against the valve outlet
B seals on: on the thread flanks with PTFE tape or paste
Part needed: CGA-320 inlet stem with a 1/4 male NPT tail

The part to buy

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A regulator inlet stem is a CGA-320 nut on one end and a 1/4 male NPT on the other, so it screws a CGA-320 cylinder onto a regulator body that has a 1/4 NPT inlet. The CGA-320 nut seals on its washer against the tank; the 1/4 NPT is taped into the regulator.

Two opposite sealing rules on one stem. Tape the 1/4 NPT end because it is tapered and seals on the thread; never tape the CGA-320 nut, which seals on a captive washer. Mixing these up is the usual reason a rebuilt inlet hisses.

Related connections

CGA-320 CO2 cylinder valve0.825"-14 NGO RH 1/4" NPT1/4-18 NPT 1/4" NPT to MFL male flare (1/4")adapter CGA-320 CO2 cylinder valve to W21.8 CO2 cylinder valveadapter CGA-320 CO2 cylinder valve to G5/8 regulator inletadapter TR21-4 soda cylinder valve to CGA-320 CO2 cylinder valveadapter

Sources: CGA-320 CO2 cylinder valve outlet thread reference (0.825in-14 NGO, RH) · CO2Art guide to cylinder connections (CGA320, W21.8, DIN477, BS341, G5/8, TR21-4) · MoreFlavor thread types explained (MFL/FFL, NPT, BSP)