AN ACR B757 FLC HAS THE L HYD SYS LOSE ITS FLUID DURING CLBOUT. THE FLC RETURNS TO THEIR DEP ARPT WHERE THEY MAKE A SAFE LNDG; HOWEVER; WITH FLAPS AT 30 DEGS INSTEAD OF AT 20 DEGS DUE TO SOME CONFUSION WITH THE CHKLIST.

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THE FO WAS FLYING THE DRAKE SID AND HAD JUST TURNED N WHILE CLBING TO 8000 FT. THE EICAS RPTED 'L HYD QUANTITY.' WE LOOKED AT THE STATUS PAGE AND SAW THE L SYS AT .47 AND DECREASING. I GOT MY QRH AND OPENED TO 'L HYD QUANTITY.' AT THAT POINT; I TOOK THE AIRPLANE AND HANDED THE QRH TO THE FO; ASKING HIM TO READ THE CHKLIST. HE READ 'CREW AWARENESS.' THEN WE GOT NUMEROUS EICAS MESSAGES ASSOCIATED WITH L HYD FAILURE. WE THEN STARTED THE 'HYD SYS PRESSURE' QRH CHKLIST. WE TURNED OFF THE PUMP SWITCHES AS PER THIS CHKLIST. THE FO THEN CONTACTED DISPATCH AND MAINT FOR A RETURN TO PHX. HE THEN INFORMED ATC OF OUR HYD PROB AND OUR NEED TO RETURN. THEY SAID 'IF YOU ARE DECLARING AN EMER; PLEASE STATE SOULS ON BOARD AND FUEL.' THE FO GAVE THEM THE REQUESTED INFO. I THEN DIRECTED HIM TO INFORM THE FLT ATTENDANTS (ADVISING THEM THAT THERE WOULD BE NO EVAC AND BRACING WAS NOT NECESSARY) AND TO MAKE A PA TO INFORM THE PAX. WE BEGAN PREP FOR LNDG. WE USED ALTERNATE FLAP AND GEAR EXTENSION; COMPLETING THE LNDG CHKLIST; AND LANDED UNEVENTFULLY. WE LATER DISCOVERED THAT WE HAD INCORRECTLY USED FLAPS 30 DEGS INSTEAD OF FLAPS 20 DEGS FOR LNDG; DUE TO SOME CONFUSION WITH THE QRH CHKLIST. ON FINAL; I HAD SPECIFICALLY QUESTIONED THE FO REGARDING THE LNDG FLAP SETTING. WE BOTH LOOKED DOWN AT THE CHKLIST AND READ 'EXTEND FLAPS AS REQUIRED' WITHOUT A SPECIFIC SETTING. IN REVIEWING THE PROC; WE DISCOVERED THAT THIS CHKLIST SHOULD HAVE CLRLY DIRECTED US TO A DIFFERENT CHKLIST THAN THE ONE WE WERE USING. THE LANGUAGE IN THE CHKLIST IS VAGUE AND ALLOWS A CREW TO EASILY FOLLOW AN INCORRECT PATHWAY AND NEEDS TO BE SPECIFIC AND DIRECTIVE. FACTORS CONTRIBUTING TO THIS ERROR INCLUDED OUR CLOSE PROX TO THE ARPT; COMPRESSING THE TIME AVAILABLE TO COMPLETE THE CHKLIST. ALSO; JUST 2 DAYS PRIOR; THERE HAD BEEN ANOTHER B757 IN OUR FLEET WITH THE IDENTICAL PROB THAT HAD RECEIVED MEDIA COVERAGE. THIS; COUPLED WITH THE FACT THAT THE B757 HAS NO MANUAL REVERSION CAPABILITY; AND A RECENT SERIES OF HYD PROBS; MADE ME LESS COMFORTABLE WITH THE IDEA THAT THIS WAS A 'NORMAL' MALFUNCTION. THIS LED ME TO BELIEVE THAT THE SAFEST COURSE OF ACTION WAS TO GET THE AIRPLANE ON THE GND ASAP.