Not compatible. EVABarrier 4mm ID x 8mm OD line and EVABarrier 5mm ID x 8mm OD line do not share a mating thread, so there is no adapter between them; fit the part that matches your hardware. Sealing method, the real-world trap, and the exact part to buy.

Updated 05 September 2026.

Bench / Fittings / Join

Connect EVABarrier 4mm ID x 8mm OD line to EVABarrier 5mm ID x 8mm OD line

How to join 4 mm ID / 8 mm OD and 5 mm ID / 8 mm OD, and what stops it leaking.

End AEVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)Will not connectEnd BEVABarrier 5mm ID x 8mm OD line (5 mm ID / 8 mm OD)

Not compatible. EVABarrier 4mm ID x 8mm OD line and EVABarrier 5mm ID x 8mm OD line do not share a mating thread, so there is no adapter between them; fit the part that matches your hardware.

The two ends

End A: EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)
End B: EVABarrier 5mm ID x 8mm OD line (5 mm ID / 8 mm OD)
A seals on: the 8mm OD is what a Duotight 8mm or John Guest 5/16 collet grips
B seals on: the 8mm OD is what a Duotight 8mm or John Guest 5/16 collet grips
Part needed: matched replacement, no adapter exists

The part to buy

Shop the bore that matches the line duty, both on 8mm fittings on Amazonaffiliate Find the bore that matches the line duty, both on 8mm fittings on eBayaffiliate

The 4mm ID and 5mm ID EVABarrier lines are both 8mm on the outside, so they use the same 8mm fittings, but you pick one or the other by duty rather than joining them: 4mm bore for gas, 5mm bore for beer.

Because both are 8mm OD they look identical once fitted, so label your gas and beer lines. Running a 4mm gas line as a long beer line pours slowly, and a 5mm beer line as a gas jumper is simply wider than it needs to be.

Related connections

EVABarrier 4mm ID x 8mm OD line4 mm ID / 8 mm OD EVABarrier 5mm ID x 8mm OD line5 mm ID / 8 mm OD EVABarrier 4mm ID x 8mm OD line to Duotight 8mm push-indirect EVABarrier 5mm ID x 8mm OD line to Duotight 8mm push-indirect Duotight ball-lock gas QD (8mm) to EVABarrier 4mm ID x 8mm OD linedirect Duotight ball-lock liquid QD (8mm) to EVABarrier 5mm ID x 8mm OD linedirect

Questions and answers

Connect EVABarrier 4mm ID x 8mm OD line to EVABarrier 5mm ID x 8mm OD line?

Not compatible. EVABarrier 4mm ID x 8mm OD line and EVABarrier 5mm ID x 8mm OD line do not share a mating thread, so there is no adapter between them; fit the part that matches your hardware.