In new construction, the plumber will install a separate vent for any plumbing fixture that does not use the vanity vent. If a fixture has its own vent line, the line will run vertically to the attic and tie into the vent-and-soil stack if possible. If not, a separate roof exit is necessary. Alternately, the vent pipe can exit the home through an exterior wall, with the opening covered by a vent plate.