Narrative:

The flight crew of a B737-300 reported that their forward lavatory was over-svced and requested maintenance to investigate the situation. I was dispatched to the gate and determined after removing the toilet shroud that the dump cable was broken where it attached to the primary dump valve. I proceeded to manually open the valve and empty the contents of the lavatory holding tank. In coordination with our company's maintenance control, I entered a discrepancy in the aircraft logbook as a maintenance note so that the lavatory could still be used but had to be manually dumped. This is the policy of our company in order to reduce passenger inconvenience rather than placing the lavatory inoperative under a MEL. I affixed a temporary placard (tape) with information that the lavatory had to be manually dumped. The aircraft was supposed to terminate that night at a maintenance base where the cable would be replaced. The aircraft was later rerouted and terminated in a non-maintenance base. 3 days later after takeoff, the lavatory overflowed and the fluid seeped to approximately the 3RD row of seats. The fluid also penetrated through the floor and seeped into the main east&east compartment into the E-1 rack. At that point, the captain lost primary airspeed, altitude and ground proximity information. After landing, maintenance determined that the following components had evidence of blue water damage: #1+2 daa, #1+2 air data computer, #1 stall management computer, #1+2 FCC and #1 FMC. Ramp personnel who were unaware that the system was inoperative and that alternate procedures should be used had svced the lavatory at the departure station. In addition, the captain did not realize that the significance of the maintenance note since only mels are listed on his dispatch release. Also, this aircraft has 2 dump valves unlike the majority of our B737's which only have one. Given the right set of circumstances, the lavatory might appear to dump properly since the secondary valve was still operating and fluid might have been trapped in the drain line from a previous manual dumping. The placard that I had affixed to the panel was missing after the incident.

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Original NASA ASRS Text

Title: A B737-300 FORWARD LAVATORY WASTE TANK DUMP CABLE WAS FOUND BROKEN AND THE ITEM WAS NOT DEFERRED PER THE MEL BUT MADE A LOGBOOK 'NOTE.' WITH NO DEFERRED ITEM DOWN- LINE STATIONS WERE NOT MADE AWARE OF THE NECESSITY FOR MANUALLY DUMPING THE TANK BEFORE SVCING AND THIS RESULTED IN AN OVER-SERVICED TANK THAT SPILLED OVER ON ROTATION INCURRING EQUIP DAMAGE.

Narrative: THE FLC OF A B737-300 RPTED THAT THEIR FORWARD LAVATORY WAS OVER-SVCED AND REQUESTED MAINT TO INVESTIGATE THE SIT. I WAS DISPATCHED TO THE GATE AND DETERMINED AFTER REMOVING THE TOILET SHROUD THAT THE DUMP CABLE WAS BROKEN WHERE IT ATTACHED TO THE PRIMARY DUMP VALVE. I PROCEEDED TO MANUALLY OPEN THE VALVE AND EMPTY THE CONTENTS OF THE LAVATORY HOLDING TANK. IN COORD WITH OUR COMPANY'S MAINT CTL, I ENTERED A DISCREPANCY IN THE ACFT LOGBOOK AS A MAINT NOTE SO THAT THE LAVATORY COULD STILL BE USED BUT HAD TO BE MANUALLY DUMPED. THIS IS THE POLICY OF OUR COMPANY IN ORDER TO REDUCE PAX INCONVENIENCE RATHER THAN PLACING THE LAVATORY INOP UNDER A MEL. I AFFIXED A TEMPORARY PLACARD (TAPE) WITH INFO THAT THE LAVATORY HAD TO BE MANUALLY DUMPED. THE ACFT WAS SUPPOSED TO TERMINATE THAT NIGHT AT A MAINT BASE WHERE THE CABLE WOULD BE REPLACED. THE ACFT WAS LATER REROUTED AND TERMINATED IN A NON-MAINT BASE. 3 DAYS LATER AFTER TKOF, THE LAVATORY OVERFLOWED AND THE FLUID SEEPED TO APPROX THE 3RD ROW OF SEATS. THE FLUID ALSO PENETRATED THROUGH THE FLOOR AND SEEPED INTO THE MAIN E&E COMPARTMENT INTO THE E-1 RACK. AT THAT POINT, THE CAPT LOST PRIMARY AIRSPD, ALT AND GND PROX INFO. AFTER LNDG, MAINT DETERMINED THAT THE FOLLOWING COMPONENTS HAD EVIDENCE OF BLUE WATER DAMAGE: #1+2 DAA, #1+2 ADC, #1 STALL MGMNT COMPUTER, #1+2 FCC AND #1 FMC. RAMP PERSONNEL WHO WERE UNAWARE THAT THE SYS WAS INOP AND THAT ALTERNATE PROCS SHOULD BE USED HAD SVCED THE LAVATORY AT THE DEP STATION. IN ADDITION, THE CAPT DID NOT REALIZE THAT THE SIGNIFICANCE OF THE MAINT NOTE SINCE ONLY MELS ARE LISTED ON HIS DISPATCH RELEASE. ALSO, THIS ACFT HAS 2 DUMP VALVES UNLIKE THE MAJORITY OF OUR B737'S WHICH ONLY HAVE ONE. GIVEN THE RIGHT SET OF CIRCUMSTANCES, THE LAVATORY MIGHT APPEAR TO DUMP PROPERLY SINCE THE SECONDARY VALVE WAS STILL OPERATING AND FLUID MIGHT HAVE BEEN TRAPPED IN THE DRAIN LINE FROM A PREVIOUS MANUAL DUMPING. THE PLACARD THAT I HAD AFFIXED TO THE PANEL WAS MISSING AFTER THE INCIDENT.

Data retrieved from NASA's ASRS site as of July 2007 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.