As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RELIEF VALVE IS INSTALLED ON HEATER ASSY: FAILURE CAUSED ENTIRE WATER SYSTEM TO DRAIN INTO FUSELAGE. THIS RELIEF VALVE SHOULD BE PLUMBED INTO EXISTING AIRCRAFT DRAIN SYSTEM, SO WATER FLOWS OUT DRAIN MAST INSTEAD OF OUT THE FUSELAGE DRAIN HOLES.