What was found
(CAN) APPROXIMATELY 1HR SOUTH HYDRAULIC QUANTITY LEVEL ON NR 1 BEGAN TO DROP. A PATCH WAS DONE THROUGH SFO AND MOC THRU DISPATCH. THE LEVEL CONTINUED TO DROP TILL IT WENT INTO THE BLUE LEVEL. NR 1 EDP FAILED. CREW DECLARED A PAN PAN ABOUT 15 MINS OUT. CFR EQUIPMENT WAS ON STAND BY PASSENGERS WERE BRIEFED BY CREW, ACFT LANDED NORMALLY AND CAME TO COMPLETE STOP ON 17R AND WAS INSPECTED. CLEARED TO TAXI UNDER OWN POWER TO GATE. NO ADVERSE PAX REACTION RESOLUTION: ENGINE NR 1 EDP REPLACED IAW AMM 29-11-01-401 AND INSPECTION CARRIED OUT IAW 05-50-23.