(You may skip this step and do it at the wiring phase, routing wires and tubes together.)
Attach vacuum tube to the pump side port:
Route the tube to the valve, middle port, cut to suitable length. Cut about 30 cm of the tube and push it into the pickup tube. About 5 cm is fine; the plastic tube outer diameter is equal to the pickup steel tube inner diameter and the plastic tube is a bit sticky. This is all sealing we need, and the friction between the tubes is still low enough that it allows rotation of the steel tube. Plug the other end to the valve, outer port. Here, the tube is represented by a green line – sorry for my poor free-hand drawing skills!:
