A B737-700 ON CLBOUT DECLARED AN EMER AND RETURNED TO THE DEP ARPT DUE TO A RPTED R WING FUEL LEAK.

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AFTER DEPARTING ZZZ; DURING CLBOUT; ZZZ TWR INFORMED US OF RPTED POSSIBLE LIQUID OR FUEL LEAKING FROM OUR R WING. TWR ASKED WHAT OUR PLAN WAS AND WE INFORMED THEM WE WOULD CONTINUE. THE CAPT CHKED IN WITH DEP AND AT THAT TIME WE BEGAN TO ASSESS THE SITUATION. THE CTR TANK FUEL GAUGE APPEARED TO BE COUNTING DOWN FASTER THAN NORMAL. AT THAT TIME WE ADVISED ATC WE WOULD LIKE TO RETURN TO ZZZ. I LEVELED THE JET AT 6000 FT AND RECEIVED RADAR VECTORS TO RETURN TO ZZZ. WE THEN ADVISED ATC WE WANTED THE LONG RWY AND TO HAVE CFR ESCORT US BACK TO THE GATE. AT THIS TIME WE COMPLETED THE APPROPRIATE CHKLISTS AND DISCUSSED THE OVERWT LNDG CONSIDERATIONS. THE CAPT ADVISED DISPATCH AND FLT ATTENDANTS OF RETURN TO ZZZ WITH A NORMAL LNDG. CAPT MADE PA TO PAX ABOUT RETURN; FOLLOWED BY A NORMAL LNDG BUT THAT THE CFR TRUCKS WOULD ESCORT US TO THE GATE AND TO NOT BE ALARMED. APCH AND OVERWT LNDG WAS ACCOMPLISHED WITHOUT INCIDENT TOUCHDOWN APPROX 200 FPM DSCNT; FLAPS 30 DEGS; 149 KTS. AT THE GATE CFR ADVISED US THEY HAD OBSERVED A VAPOR TRAIL STREAMING FROM OUR R WING ON SHORT FINAL BUT DID NOT OBSERVE IT ON TAXI IN. AT THE GATE A VISUAL INSPECTION BY FLT CREW FOUND FUEL WAS ON THE UNDERSIDE OF THE R WING AND WAS OBSERVED DRIPPING ONTO THE GND AT ABOUT MID WING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FUEL STREAMING FROM THE R WING VENT TUBE WAS RPTED BY THE TWR AND A COMPANY ACFT. ON RETURN TO THE FIELD THE VENT TANK OUTLET STILL HAD A SMALL DRIP. THE CAUSE OF THE INCIDENT WAS OVER-FUELING OF THE R WING AND OVERFLOW ENTERING THE VENT TANK. THIS TANK WILL NORMALLY DRAIN INTO THE MAIN TANK AS THE LEVEL DROPS.