These connect directly. Inline gas check valve mates with MFL male flare (1/4") without an adapter. Sealing method, the real-world trap, and the exact part to buy.
Updated 05 September 2026.
Connect Inline gas check valve to MFL male flare (1/4")
How to join 1/4" FFL x 1/4" MFL and 1/4" MFL (7/16"-20 UNF), and what stops it leaking.
These connect directly. Inline gas check valve mates with MFL male flare (1/4") without an adapter.
The two ends
- End A
- Inline gas check valve (1/4" FFL x 1/4" MFL)
- End B
- MFL male flare (1/4") (1/4" MFL (7/16"-20 UNF))
- A seals on
- flare faces at each flare end; barb under a clamp on barb versions
- B seals on
- metal 45 degree flare face, never PTFE tape
- Part needed
- none, direct fit
A common inline gas check valve has a 1/4 FFL inlet and a 1/4 MFL outlet, so it drops into a flare gas line between the regulator and the keg: the FFL takes the upstream male flare, the MFL feeds the downstream FFL swivel.
The check valve is directional, so fit it facing the keg or it blocks the CO2 you are adding. Both ends seal on their flare faces, so keep them clean and tape free, and put it on the gas line only, never the beer line where it would stop the pour.
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Questions and answers
Connect Inline gas check valve to MFL male flare (1/4")?
These connect directly. Inline gas check valve mates with MFL male flare (1/4") without an adapter.