[Brucee]

the same size of rubber hose is used for vacuum lines on a wide variety of cars. Because it only sees a few psi vacuum, unreinforced rubber hose is good enough; it just needs to fit OK, be oil resistant, and be thick-walled enough that it won't collapse under the vacuum.


I've replaced 'all rubber' lines with 4mm plastic pneumatic line (as is fitted in many cases anyway), and the rubber hose (for joiners) can be found such that it will fit over barbed spigots of ~5mm diameter, +/- a bit. 'T' pieces meant for windscreen washer plumbing are usually just fine in vacuum lines.

A good trick is that the 4mm plastic pneumatic hose can be heated at the ends (using a naked flame) and this usually creates a sort of flare/barb. Once cool, 4mm line ends so treated are a more snug fit in typical rubber hose.

cheers