What was found
FLIGHT 8663, ON CLIMB ANC - FAI AIR TURNBACK/DISCREPANCY: DURING CLIMB, THE CREW RECEIVED A DADC DATA INVALID MESSAGE, FOLLOWED BY AN ANTI - ICE FAULT, AMP FAULT AND THE FDAU LIGHT WAS FLASHING ON FEDEP PANEL. AIRCRAFT WAS RETURNED TO ANC, NO EMERGENCY WAS DECLARED. SDR WITH CORRECTIVE ACTION WILL FOLLOW. MAINTENANCE COULD NOT DUPLICATE THE FDAU, APM & ANTI-ICE FAULTS. FOUND BLOWN DRAIN LINE, CRACKED FITTING & DEFECTIVE DRAIN VALVES ON CA SIDE. REPLACED ALL ITEMS. A SECONDARY LEAK WAS FOUND ON FO SIDE. REPLACED BAD ELBOW, RING & UNION. ALL STATIC LEAKS REPAIRED; ALL OPS & LEAK CHECKS GOOD. OCF COMPLETED WITH NO DEFECTS NOTED.