: I am in the process building a utility room where I will be moving my washing machine to another location and adding a sink to a new location. The washing machine was drained and vented with the pipes exposed outside the wall. When I move them I would like to put the pipes in the wall. Do I need vents for the sink and the washing machine? Can I Leave the vent in the wall, or does it have to run through the roof. The sink and the washing machine will be the only drains on this line.