As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WATER LEAKING FROM FIRST CLASS LAVATORY IN FLIGHT. STARTING AFTER TAKE OFF STREAM OF DIRTY WATER INTO GALLEY. TROUBLESHOT THE LEAK TO A CLOG IN THE AFT LAVATORY AND GALLEY DRAIN LINE AFTER THE TWO JOIN GOING TO THE FWD DRAIN MAST. CONFIRMED THE CLOG WAS CAUSING THE DRAIN WATER TO BACK UP THRU THE LAVATORY VENT. CLEARED THE CLOG, ALL OPS OK IAW AMM 38-31-00-910-801.