As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - THE LAVATORY SMOKE DETECTOR SOUNDED SHORTLY AFTER TAKEOFF. THE LAVATORY AND LAVATORY WASTE WAS CHECKED FOR EVIDENCE OF SMOKE AND BURNING ODOR. NONE WAS NOTED. THE LAVATORY DETECTOR WAS RESET AND THE OPERATIONAL CHECK WAS GOOD. AIRCRAFT RETURNED TO SERVICE.