Backflow assembly has bad check valve and relief drain. Order factory oem parts and rebuild 2 inch RPBA. 11/19/20 While performing rebuild on 2 inch RPBA noticed that the check valve retainer plate is missing from assembly. Could not find it around unit. Will need to order new part and reschedule. 12/3/20 Performed rebuild on 2 inch RPBA for premise isolation and irrigation. Replaced both check valves and relief valve. Tested device. Passed test. Will forward test results to local water purveyor.