We live in a house built in 1979, and the builder subbed a drain pipe in the basement concrete for a wet bar. They installed it far too close to the wall to build a bar, but too far from a wall to be useful in any way. We have enclosed it in a small room behind a fish tank, and we want to make a small utility sink to drain the tank. It doesn't have a water source, and it is awkwardly positioned in the room, even in this application. I was looking through a home improvement book and saw a photograph of a basement subbed for a bath and it showed a sink vent. Our drain most certainly doesn't have a vent. Is this an issue? Does every sink/drain need venting, or is it enough that (hopefully) the other drains in the house are vented?