As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED-WHILE IN ROUTE PACK TWO VALVE CLOSED. FLIGHT ATTENDANT SAID SHE HEARD THE HOSE BLOW OFF. THEY WERE CLIMBING THROUGH 23,000 FEET AND LEVELED OUT AT 25,000 FOR SINGLE PACK ALTITUDE. A COUPLE MINUTES LATER THE CABIN ALTITUDE STARTED TO CLIMB AGGRESSIVELY. CREW DECIDED TO RETURN TO OAK. CORRECTIVE ACTION- REMOVED AND REPLACED BLOWN DUCT IN PAC 1 AND REMOVED AND REPLACE DAMAGED AND LEAKING DUCT IN PAC 2. OPS AND PRESSURE CHECK GOOD.