A DEHAVILLAND DASH 8 ON APCH EXPERIENCED LOSS OF #1 HYD SYS PRESSURE AND QUANTITY CAUSED BY AN IMPROPERLY INSTALLED HYD LINE.

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OUR FLT TOOK US FROM ZZZ1 TO ZZZ ON THE GND. I NOTICED THE #1 HYD QUANTITY WAS LOW; SO I XFERRED FLUID FROM THE #2 SIDE TO THE #1 SIDE. THIS IS COMPLETELY ROUTINE. ABOUT 1/2 WAY TO ZZZ; I NOTICED THAT THE #1 SIDE HAD DROPPED A LITTLE BUT I HAD SEEN THAT BEFORE AND SIMPLY MONITORED THE #1 QUANTITY. AS THE FLT PROGRESSED; I NOTICED THAT THE #1 QUANTITY APPEARED TO BE DROPPING VERY SLOWLY. AT THIS STAGE THE QUANTITY HAD NOT REACHED A LEVEL WHERE I BELIEVED WE'D RUN OUT OF FLUID BEFORE WE ARRIVED IN ZZZ. THE FO AND MYSELF DISCUSSED THE VARIOUS THINGS THAT MIGHT HAPPEN AND HOW WE SHOULD PROCEED. AS IT TURNED OUT WE HAD TO ADD PWR TO CLR THE RWY. THE #1 HYD SYS PROVIDES SVC TO: NORMAL BRAKES; INBOARD ROLL SPOILERS; FLAPS; AND THE #1 RUDDER ACTUATOR. WE GOT THE FLAPS DOWN TO THE LNDG CONFIGN AND MADE A NORMAL LNDG. THE FO (PF) MADE SOME COMMENT AFTER THE LNDG THAT THE CTL BECAME SOMEWHAT SLUGGISH. AFTER WE LANDED AND SLOWED DOWN; I TOOK THE CTLS AND TESTED THE TOE BRAKES. THEY DIDN'T WORK AT ALL. I PROCEEDED TO THE GATE SLOWLY USING THE EMER BRAKES TO SLOW THE TAXI SPD ONLY A COUPLE OF TIMES. THE INVESTIGATING MECH FOUND AN IMPROPERLY INSTALLED HYD LINE THAT WAS BEING ABRADED BY THE NORMAL OP OF THE LNDG GEAR. A SMALL HOLE GOT WORN INTO THE STEEL TUBE BY THE LNDG GEAR MECHANISM CAUSING THE LEAK.