I bought a house that had the basement completed by the previous owner. It appears the contractor vented the downstairs bathroom into the main level kitchen sink pipes. There is a sewer vent in the kitchen sink line which secretes a very bad sewer odor. Why would a plumber run an open sewer vent inside the house? Can this be closed up and the bathroom vented into the unfinished space still in the basement? I can get to the bathroom pipes.