According to one aspect of the present disclosure, a plumbing drain assembly is disclosed which includes a plumbing outlet box, a Y connector, and an air intake valve. The plumbing outlet box has a back wall and four sidewalls that extend outward from the back wall to form a cavity. The Y connector includes a first and second drain channels. The first drain channel is mounted in the cavity and has opposing first and second ends. The second drain channel merges with the first drain channel between the first and second ends. The air intake valve is mounted to the first end of the first drain channel, and is configured to allow exterior air to enter into the first drain channel through the first end, and prevent internal air from exiting the first drain channel through the first end.