As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING INSTALLATION OF THE PITOT/STATIC DRAIN VALVE MOD, S2 DRAIN RESERVOIR WAS FULL OF WATER WHEN IT WAS DISASSEMBLED. UPON INSPECTION OF THE RESERVOIR BODY, THE WATER HAD FROZEN AND BULGED THE RESERVOIR SIDES. ALL PITOT AND STATIC DRAIN VALVES WERE SEALED FROM THE OUTSIDE WITH A SEALANT.