[Wavery]

I'm with Shane..... "Where's the P-trap?"

That sink drains into the grey water tank. Nothing smells worse than a grey water tanks after a day or two. If you have no P-trap, the grey water tank's fumes will come right up that drain pipe and stink you out of your camper.

The purpose of the "U" in the P-trap is to block fumes and insects from coming up the drain pipe. That "U" stays full of water and acts like a plug until water goes down the drain from the sink.