Abstract: A drain vent apparatus for recreational vehicles may be coupled to the drain vent of a drain line of a vehicle and includes a coupling for a drain hose for the output of the drain vent. The drain vent has an outer housing and an inner pipe located in said outer housing and connected to the coupling for the drain vent for coupling to a drain line of a vehicle. The outer housing forms an annular passageway around the inner pipe for the passage of air and a check valve is located in the outer housing passageway to allow the passage of air in one direction while blocking the passage of water in the opposite direction so that the outside vent air may pass into the drain vent to vent the drain line. The outer housing has an opening to atmosphere covered by a cap. The check valve may be mounted adjacent to the opening in the passageway adjacent the cap so that removal of the cap allows access to the check valve.