As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4222 - AFTER TAKEOFF FROM GPT, CAPTAIN REPORTED LAVATORY SMOKE DETECTOR SOUNDING. AIRCRAFT RETURNED TO GPT AND LANDED SAFELY. MAINTENANCE REMOVED AND REPLACED BATTERY IN LAVATORY SMOKE DETECTOR. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE. (M)