Air leak 2005 trail star end dump

[Moose]

That is the leveling valve for the suspension. The tube you're pointing to should be the exhaust port. Some people put a tube on it like that and some will have the mesh-type mufflers. It slows the exhaust flow so that during operation it doesn't expel excessive amounts of air and cause the compressor to work harder than it needs to. It will also quiet it down and kind of help it from getting clogged. If the trailer is aired up properly, the suspension is at it's ride height and you still have air coming out of that tube you need to rebuild or replace the valve.