Abstract: A toilet ventilating system for use with a bowl incorporating a sewer line connection and including an upstanding vent conduit leading from the bowl rim outlets to an elevated cross over in the water storage tank and then dropping downwardly to form an exhaust conduit connected with the sewer connection. A centrifugal fan having a flow rate of 60 cubic feet per minute is incorporated in the vent conduit and a trap valve is incorporated in the cross over for selectively opening and closing communication between the vent conduit and the exhaust conduit. The trap valve incorporates a floating cylinder, positioning of which is controlled by water pumped from an elevated reservoir through a positive displacement pump. A controller is provided for controlling the positive displacement pump to open the trap valve, actuation of the centrifugal fan and closure of the trap valve, deactuation of the fan and actuation of the flush valve.