Narrative:

[While enroute]; the right center fuel pump press illuminated with the corresponding EICAS message. We turned off both left and right center fuel pumps; as per SOP. Everything appeared normal at that point. Approximately 10 minutes later we got a fuel config advisory EICAS message and I looked up and saw the fuel config light illuminated on the fuel panel. At first; I assumed it was just a 2000 lb fuel imbalance and told my first officer to pull out the QRH to balance the fuel per SOP. She did pull out the QRH; but said; 'we have a fuel leak!' I stared up at fuel panel and also saw the quantity in the right fuel tank dropping a few hundred pounds just as I was watching it. At that point we both confirmed that we had a fuel leak. I quickly typed a message to dispatch; saying; 'call me as soon as possible' and started the fuel leak checklist in the QRH. The checklist specifically said; 'do not try to balance the fuel (i.e.; using the fuel config checklist); but once you determine an actual fuel leak; land immediately at the nearest suitable airport.' I called back to the a flight attendant and asked her to look out the right window for any possible fuel leaking from the engine or the wing--she called back promptly and reported no fluid/fuel leaking at all.dispatch sent us a VHF frequency and I immediately called her; telling her that we had a definite fuel leak and that we needed to divert immediately. I asked dispatch where would be a good divert field and she recommended [an alternate airport]; about :30 minutes away. My first officer and I agreed. Somewhere during this time I told my first officer that I would take over the flying and that she work the radios and the checklist. I told her to declare an emergency with ATC and we immediately get a vector toward [our alternate]. Simultaneously I put [the alternate] in the alternate page of the FMC and executed the 'divert now' prompt. Once headed towards [the alternate]; I called back to the a flight attendant and went over the [cabin preparation] components; telling her that we had a fuel leak; to prep for evacuation (at that point; I wasn't sure how bad the fuel imbalance would be when we got to [the alternate] (it was at 3000 lbs and getting worse); or if the aircraft could even be safely landed; so I wanted her to prep for evac; no special instructions; and time to landing was :30 minutes). I then got on the PA and made an announcement to the passengers; saying we have a fuel leak and we needed to divert and that we would be landing in 30 minutes. Dispatch contacted again about 5 minutes later and asked us to divert to [a different alternate]. I told my first officer to tell dispatch; 'negative--we've [advised ATC] and are preceding directly to [the first alternate]'. I understand that [the second alternate] is our maintenance hub and it would be easier to get our passengers to their final destinations if we went [there]; however; [it] is not the 'nearest suitable airport'; and most importantly; our fuel imbalance would be significantly worse if we had to fly [to the second alternate].my first officer and I completed the fuel leak checklist. There was a part that mentioned shutting down an engine so that you can balance the fuel. I thought about it and told my first officer that when I got to [the alternate] and clicked off the auto pilot; if the aircraft rolled excessively or was unable to land safely; then we would shut the engine down and balance the fuel (we had plenty of fuel; so fuel wasn't a problem). Until then; I was not going to shut down an engine. We landed safely. There was a 4000 lb fuel imbalance when we landed. The mechanic also told me when I went back to get my bags a few hours later; that [the company] called him and ask that he [defer] it so that we could continue on. He told them 'no; that there was a fuel imbalance of 4000 lbs and that there was a definite fuel leak.'

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Original NASA ASRS Text

Title: B757 Captain reported they diverted to an alternate after experiencing a fuel leak.

Narrative: [While enroute]; the R Center Fuel Pump Press illuminated with the corresponding EICAS message. We turned off both L and R Center Fuel Pumps; as per SOP. Everything appeared normal at that point. Approximately 10 minutes later we got a Fuel Config Advisory EICAS message and I looked up and saw the Fuel Config light illuminated on the Fuel Panel. At first; I assumed it was just a 2000 lb fuel imbalance and told my FO to pull out the QRH to balance the fuel per SOP. She did pull out the QRH; but said; 'We have a fuel leak!' I stared up at fuel panel and also saw the quantity in the right fuel tank dropping a few hundred pounds just as I was watching it. At that point we both confirmed that we had a fuel leak. I quickly typed a message to Dispatch; saying; 'Call me ASAP' and started the Fuel Leak Checklist in the QRH. The checklist specifically said; 'Do NOT try to balance the fuel (i.e.; Using the Fuel Config checklist); but once you determine an actual fuel leak; land immediately at the nearest suitable airport.' I called back to the A Flight Attendant and asked her to look out the right window for any possible fuel leaking from the engine or the wing--she called back promptly and reported no fluid/fuel leaking at all.Dispatch sent us a VHF frequency and I immediately called her; telling her that we had a definite fuel leak and that we needed to divert immediately. I asked Dispatch where would be a good divert field and she recommended [an alternate airport]; about :30 minutes away. My FO and I agreed. Somewhere during this time I told my FO that I would take over the flying and that she work the radios and the checklist. I told her to declare an Emergency with ATC and we immediately get a vector toward [our alternate]. Simultaneously I put [the alternate] in the ALTERNATE page of the FMC and executed the 'Divert Now' prompt. Once headed towards [the alternate]; I called back to the A Flight Attendant and went over the [cabin preparation] components; telling her that we had a fuel leak; to prep for evacuation (at that point; I wasn't sure how bad the fuel imbalance would be when we got to [the alternate] (it was at 3000 lbs and getting worse); or if the aircraft could even be safely landed; so I wanted her to prep for evac; no special instructions; and time to landing was :30 minutes). I then got on the PA and made an announcement to the passengers; saying we have a fuel leak and we needed to divert and that we would be landing in 30 minutes. Dispatch contacted again about 5 minutes later and asked us to divert to [a different alternate]. I told my FO to tell Dispatch; 'Negative--we've [advised ATC] and are preceding directly to [the first alternate]'. I understand that [the second alternate] is our maintenance hub and it would be easier to get our passengers to their final destinations if we went [there]; however; [it] is NOT the 'Nearest suitable airport'; and most importantly; our fuel imbalance would be significantly worse if we had to fly [to the second alternate].My FO and I completed the Fuel Leak Checklist. There was a part that mentioned shutting down an engine so that you can balance the fuel. I thought about it and told my FO that when I got to [the alternate] and clicked off the auto pilot; if the aircraft rolled excessively or was unable to land safely; then we would shut the engine down and balance the fuel (we had plenty of fuel; so fuel wasn't a problem). Until then; I was not going to shut down an engine. We landed safely. There was a 4000 lb fuel imbalance when we landed. The mechanic also told me when I went back to get my bags a few hours later; that [the Company] called him and ask that he [defer] it so that we could continue on. He told them 'No; that there was a fuel imbalance of 4000 lbs and that there was a definite fuel leak.'

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.