As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AIRCRAFT LOST MAIN HYDRAULIC SYSTEM. LANDED USING EMERGENCY SYSTEM. WATER BOMBING PROBE SELECTOR VALVE REMOVED AND FOUND THAT THE REAR SCREW PLUG SEAL AND PLASTIC BACK UP RING HAD BLOWN OUT CAUSING HYDRAULIC PRESSURE LOSS. UNIT SENT TO OVERHAUL AGENT WHO SAID THAT 'O' RING HAD BEEN CUT BUT UNIT STILL PASSED THEIR HIGH PRESSURE TEST.