Yes my clunck reaches the bottom of the main tank. Funny thing. I went to pull all the tubing off my UAT and when I cut the fill line on the UAT, the UAT filled up with fuel. (the UAT was still connected to the main tank and the main tank had some fuel in it) The fuel from the main tank filled up the UAT... Its was like when I cut a slit in the fill line in the it started filling up with fuel from the main tank...