Air admittance valve for use in drainage systems

An air admittance valve for use in drainage systems comprising a generally circular pipe having axially opposite upper and lower end portions, said upper end portion having a free terminal edge, a cap;

• said cap having a top wall, a peripheral wall and a generally radially inwardly directed bottom wall terminating in a free edge provided with an opening corresponding to the exterior diameter of said circular pipe;
• said bottom wall having means therein for preventing insects from entering said cap, said pipe upper end portion being telescopically housed within said cap with said upper end portion free terminal edge contiguous said top wall, said pipe having a wall portion defining an air inlet opening for admitting air from said cap into said pipe, said air inlet opening being disposed at an angle of generally 45.degree. to the pipe axis, a closure for said air inlet opening located at an inboard side of said pipe wall portion, means adjacent said upper end portion free terminal edge for pivoting said closure between first and second respectively open and closed positions whereby air is admitted from said cap into said pipe through said air inlet opening when said closure is in said first position and said closure when in said second position prevents the exit of air/drainage from said pipe through said air inlet opening, a pair of generally concentric downwardly projecting spaced ribs carried by said top wall, said pair of spaced ribs defining a generally circular slot therebetween, said circular slot having an outside diameter corresponding generally to the diameter of said circular pipe, and said pipe upper terminal edge being received in said circular slot.