Narrative:

Approximately 2.5 hours into the flight; lead flight attendant called to say water was streaming out of the overhead bins and ceiling panels in first and business class on the lower level and requested a flight deck crewmember assist in the situation. The upper deck flight attendants installed the secondary barrier. Upon exiting the flight deck; I could see water flowing out of the upper deck aft lavatory. Water level toward the rear of the upper deck by the stairwell appeared to be deep. Flight attendants had spread blankets and paper towels the entire length of the upper deck in an attempt to stop the flow of water. The water appeared to be coming from the lower right side of the aft toilet. I removed the access panel and closed the water shut-off valve. From the time I left the flight deck until the time the shut-off valve was closed was about 20 seconds. From flight deck notification of the water leak to shutoff was about 3-4 minutes. I stowed the secondary barrier and proceeded down toward lower level business and first class. Water was pouring out of the overhead bins. Every first class and business passenger was out of their seats in an effort to avoid getting wet. The carpet was under a considerable amount of water and still leaking from overhead panels and bins. I returned to the flight deck; discussed the situation with the first officer. I was concerned about the amount of water and the possibility that it would affect airplane systems enter the electrical equipment bay; or cause an electrical fire. Another concern was passenger welfare with 7.5 hours of flight remaining. The decision was made to divert. We had numerous diversion options if electrical equipment began to malfunction. We woke the relief pilot to assist with the diversion. Satvoice was used to call dispatch and maintenance control. They concurred with the decision. Center informed us that they could not provide priority handling unless we declared an emergency. We declared an emergency for this reason and requested the longest runway; to minimize the possibility of hot brakes during the overweight landing roll. Descent; approach and landing were uneventful. From the decision to divert to touchdown was 30 minutes. Landing weight was 651;000 pounds. Brake temperatures after block-in were all less than 3 on the gear synoptic. The lead fire fighter came to the flight deck and informed us he was told the divert was due to carbon monoxide. We are still trying to find out how communication about a water leak had changed to a carbon monoxide incident by the time it reached the fire department. Maintenance technicians met the airplane. I showed them where the water originated in the upper deck lav. Maintenance technicians dropped several ceiling panels in first class and a considerable amount of water continued to drain. The carpeting and seats were saturated. I went to operations; reviewed the flight plan; accepted the release; and continued the trip with a different airplane. Block-in to block out was just over 2 hours.

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Original NASA ASRS Text

Title: B747 Captain is informed of a water leak in the upper deck lavatory that results in water dripping out of the overhead bins in the cabin below. The Captain is able to shut off the water but fears of electrical malfunctions and passenger comfort dictate a diversion.

Narrative: Approximately 2.5 hours into the flight; Lead Flight Attendant called to say water was streaming out of the overhead bins and ceiling panels in First and Business class on the lower level and requested a flight deck crewmember assist in the situation. The upper deck flight attendants installed the secondary barrier. Upon exiting the flight deck; I could see water flowing out of the upper deck aft lavatory. Water level toward the rear of the upper deck by the stairwell appeared to be deep. Flight Attendants had spread blankets and paper towels the entire length of the upper deck in an attempt to stop the flow of water. The water appeared to be coming from the lower right side of the aft toilet. I removed the access panel and closed the water shut-off valve. From the time I left the flight deck until the time the shut-off valve was closed was about 20 seconds. From flight deck notification of the water leak to shutoff was about 3-4 minutes. I stowed the secondary barrier and proceeded down toward lower level business and first class. Water was pouring out of the overhead bins. Every first class and business passenger was out of their seats in an effort to avoid getting wet. The carpet was under a considerable amount of water and still leaking from overhead panels and bins. I returned to the flight deck; discussed the situation with the First Officer. I was concerned about the amount of water and the possibility that it would affect airplane systems enter the electrical equipment bay; or cause an electrical fire. Another concern was passenger welfare with 7.5 hours of flight remaining. The decision was made to divert. We had numerous diversion options if electrical equipment began to malfunction. We woke the relief pilot to assist with the diversion. SATVOICE was used to call Dispatch and Maintenance Control. They concurred with the decision. Center informed us that they could not provide priority handling unless we declared an emergency. We declared an emergency for this reason and requested the longest runway; to minimize the possibility of hot brakes during the overweight landing roll. Descent; approach and landing were uneventful. From the decision to divert to touchdown was 30 minutes. Landing weight was 651;000 LBS. Brake temperatures after block-in were all less than 3 on the gear synoptic. The lead Fire Fighter came to the flight deck and informed us he was told the divert was due to Carbon Monoxide. We are still trying to find out how communication about a water leak had changed to a carbon monoxide incident by the time it reached the fire department. Maintenance technicians met the airplane. I showed them where the water originated in the upper deck lav. Maintenance technicians dropped several ceiling panels in first class and a considerable amount of water continued to drain. The carpeting and seats were saturated. I went to Operations; reviewed the flight plan; accepted the release; and continued the trip with a different airplane. Block-in to block out was just over 2 hours.

Data retrieved from NASA's ASRS site as of July 2013 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.