As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE RIGHT SIDE FUEL TANK SUMP DRAIN VALVE DIFFICULT TO CLOSE AFTER SUMPING FUEL TANK. FINALLY BECAME IMPOSSIBLE TO OPEN. REPLACED DRAIN VALVE. FOUND DRAIN VALVE CORRODED BETWEEN PLUNGER AND VALVE BODY. DRAIN VALVE NEEDS TO BE MORE CORROSION RESISTANT. THE RIGHT SIDE FUEL TANK ALWAYS IS THE SIDE THAT HAS WATER IN IT.