Connect Duotight 8mm push-in to John Guest 5/16" push-fit
How to join 8 mm (5/16") OD and 5/16" (8 mm) OD, and what stops it leaking.
Not a direct fit. Joining Duotight 8mm push-in to John Guest 5/16" push-fit needs a 8mm Duotight joiner (used with John Guest 5/16 tube).
The two ends
- End A
- Duotight 8mm push-in (8 mm (5/16") OD)
- End B
- John Guest 5/16" push-fit (5/16" (8 mm) OD)
- A seals on
- double EPDM O-ring on the tube outer wall
- B seals on
- single O-ring plus stainless collet grab-ring
- Part needed
- 8mm Duotight joiner (used with John Guest 5/16 tube)
The part to buy
Duotight 8mm and John Guest 5/16 tube are close enough that either fitting will grip either tube and the O-ring still seals, so brewers mix them freely at low pressure. The clean way is to run one tube standard and use a straight joiner where you cross systems.
5/16 inch is 7.94mm, not 8mm. The 0.06mm gap is nothing on a short gas jumper but can weep on a long, warm, high-pressure beer run. If a mixed joint leaks, standardise that run on one system rather than chasing it.
Related connections
Sources: KegLand Duotight push-in fittings (manufacturer) · KegLand EVABarrier 4mm ID x 8mm OD tubing (manufacturer) · John Guest Speedfit push-fit fitting technical data