What was found
AT FL 270 RECEIVED ECAM HYD GRN SYS LO PSI, THEN LO RESERVOIR. IMMEDIATELY TURNING OFF GRN SYS PUMPS TO PREVENT PUMP DAMAGE. CONFIRMED BOTH ECAM & OVERHEAD GRN SYS RES LOW. MANUAL GEAR EXTENSION QRH CHECKLIST. DURING DESCENT & DURING FINAL CONTINUED TO RECEIVE GRN SYS LOW PSI. ONCE ON DECK FOUND GREEN SYS LEVELS NORMAL. VERIFIED GREEN HYD QUANTITY TO BE JUST BELOW THE TOP HAT. INSPECTED & FOUND HYD LEAK IN WHEEL WELL, COMING FROM BRAKE SELECTOR, STANDBY GENERATOR VALVE. FOUND A FITTING ON VALVE MANIFOLD TO BE EXCESSIVELY LOOSE, FOUND THE O-RING DAMAGED. CLEANED FITTING & REPLACED O-RING IAW AMM 20-23-16-00, LEAK CHECKED GOOD.