What was found
AIRCRAFT RETURNED OF FLIGHT DUE TO DURING CLIMB, THERE WAS NOT POTABLE WATER IN THE LAVATORIES. PERFORMED REVISION TO LAVATORIES IAW FIM DMC-B787-A-38-10-F1-73A-421A-A PROCEDURE, SHOWING FAILURE CODE 38-12669, DETECTING THE POWER MODULE RPDU41 DAMAGED. THE POWER MODULE WAS REPLACED IAW AMM DMC-B787-A-24-71-05-00A-520A-A & 720A-A, TESTED CORRECT. THE OVERWEIGHT INSPECTION WAS NOT NECESSARY DUE TO THE ACFT LANDED WITH 169,900 KILOGRAMS & THE MAXIMUM ALLOWABLE LANDING WEIGHT IS 172, 365 KILOGRAMS.