What was found
PILOT REPORTED DURING CLIMB OUT FROM BASE AT KDMN EN ROUTE TO SENDING FACILITY HE TURNED ON THE CABIN VENTILATION AND WATER STARTED POURING OUT OF UPPER A/C VENTS. HE THEN TURNED OFF THE A/C VENT SYSTEM AND RETURNED TO BASE AND SHUT THE AIRCRAFT DOWN WITHOUT ISSUE, WROTE THE AIRCRAFT UP AND CONTACTED ON CALL MECHANIC. MECHANIC DISCOVERED AFT EVAPORATOR VENT DUCTING WAS CRACKED AND HAD ALLOWED RAIN WATER TO COLLECT AND ONCE FAN WAS TURNED ON IT PUSHED WATER THRU THE VENT SYSTEM.