Identifying a pipe

[rustytop]

Replaced most of my fuel lines on the weekend. The one across the tank joining each side is going to have to wait. My burger bap hands and sausage fingers aren't malleable enough.

My question:

There are 3 pipes coming off the expansion tanks each side of the van. The two easy ones which run virtually parallel to each other, then there is a sneeky smaller one which again runs under the van in the same direction ish. I tried to find where this mysterious third pipe runs to and could just about feel an open end? Really difficult to confirm though with the hand problems as mentioned above.

if it is open I assume it is an overflow for the expansion tank? Although surely the tank should be sealed?

Rustytop

PS the third pipe is smaller diameter and not as flexible as the others.

[Aidan]

there should be two pipes on either side one out the front breathers and one out of the tube breathers that are on top of the tank, plus the big cross link breather that is attached to the chassis, usually the flexis break up and then the pipes get pulled off because they appear to be attached to nowt