Plumbing cleanout plug

Claim 1

A BACK TRAP CONSTRUCTION FOR DRAIN PIPES AND THE LIKE OF THE TYPE HAVING A DIAMETRICALLY ENLARGED END PORTION WITH A DIAMETRICALLY ENLARGED CHAMBER THEREIN, SAID CONSTRUCTION COMPRISING AN ANCHOR COLLAR WITH ALL PORTIONS THEREOF BEING DISPOSED ENTIRELY WITHIN SAID CHAMBER, MEANS SECURING SAID COLLAR IN SAID CHAMBER IN FLUID TIGHT ENGAGEMENT WITH SAID ENLARGED END PORTION, SAID COLLAR INCLUDING A CYLINDRICAL LOWER RIM, A DIAMETRICALLY ENLARGED CYLINDRICAL UPPER RIM AND AN ANNULAR LATERALLY THICKENED PORTION CONNECTION SAID RIMS, AN ANNULAR RECESSED UPWARDLY DISPOSED SEATING SURFACE IN SAID ANNULAR PORTION DISPOSED IN SAID UPPER RIM, A BACK FLOW PREVENTING VALVE ASSEMBLY DETACHABLY MOUNTED IN SAID COLLAR, SAID VALVE ASSEMBLY COMPRISING A HOLLOW BODY PROVIDED WITH RIGIDLY CONNECTED CYLINDRICAL INNER AND OUTER SLEEVES RIGIDLY JOINED AND CLOSED AT THEIR LOWER ENDS BY AN ANNULAR WEB AND EACH EXTENDING INTO SAID COLLAR, AN ANNULAR MOUNTING FLANGE ON SAID OUTER SLEEVE SEATED ON SAID SEATING SURFACE, A VALVE SEAT ON THE LOWER END OF SAID INNER SLEEVE, A VALVE COOPERATING WITH SAID VALVE SEAT, SAID VALVE AND VALVE SEAT BEING DISPOSED BELOW SAID COLLAR, LOCKING MEANS ON THE INNER AND LOWER PORTION OF SAID LOWER RIM AND ON THE OUTER SURFACE OF SAID OUTER SLEEVE FOR RELEASABLY SECURING SAID VALVE ASSEMBLY TO SAID COLLAR.