Correct.

You MUST have an air leak at the UAT nipples to fuel/ fill lines. Using Tie-wraps to the nipples will not allow a perfect seal... use stainless steel tie-wire.

... Another overlooked problem for very few people is the use of a common screw to plug the fill line after filling... this will 'leak' as outside air will slowly follow the threads of the screw to the UAT tank.