Date: 201909
Aircraft: B737-900
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Galley Furnishing
Component problem: Failed
Reporter organization: Contracted Service
Reporter function: Technician
Human factors: Troubleshooting; Communication Breakdown; Time Pressure
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Aircraft In Service At Gate
Result: Aircraft Aircraft Damaged; General Maintenance Action
Contributing factors: Human Factors; Manuals; Procedure
Primary problem: Procedure

Narrative: Crew reported there was a water leak coming from the forward galley water shutoff valve. Mechanics contacted our Maintenance Control with IPC (illustrated Parts Catalog) references and part numbers for the shutoff valve. This created a time constraint and rushed atmosphere for me knowing that Maintenance Control was not going to issue a deferral for it and wanted it fixed ASAP! Upon inspecting the aircraft; I did find that the shutoff valve was leaking and required replacement. The exterior water service panel was opened and the pressure bled off so as to depressurize the system. I then removed the valve. While I had the valve out I was required to bring it to the shop area to remove the fitting and install them on the new valve. It was during this time that ground personnel serviced the lavatory and saw that the panel was open and thinking they were doing a good thing closed it.Well at that point; the water system air compressor started and began to pressurize the system and with the valve being removed; it flooded the galley and parts of the flight deck floors. Prior to the start of my Maintenance action I tried to find the Aircraft Maintenance Manual reference for the removal and replacement of the valve and I could not find it! This added to the confusion and rushed feeling since I had never replaced one before.Aircraft Maintenance Manual chapter XX should be revised to include the removal and replacement of this very important valve. This would have provided the lock out tag out procedures for the replacement.


Second narrative: I was called to assist in fixing a forward galley water leak. As the gate mechanic was troubleshooting the leak; he found the forward galley water shut off valve leaking from its handle. I was then asked to go bleed off the water pressure which I did by going down to the potable water service panel and opening the fill valve and bleed off the air pressure. I left the door and the fill valve open so the pressure would not build back up; thinking it wouldn't take very long I did not tag the service door.While we were prepping the new valve for installation in our maintenance garage we received a call that the forward galley and cockpit floor were flooding. I ran to the potable water service panel and found that someone had closed it up; causing the system to pressurize and thus flooding the forward galley. I opened the service panel and valve to bleed off the pressure which stopped the flow of water. Before we started the job we looked for an AMM (Aircraft Maintenance Manual) for removal and install of that valve and we could not find any AMM for this; since this was a through flight we were in a bit of a hurry to get the job done in a timely manner.We should have pulled the circuit breaker for the air compressor on the potable water system and tagged the potable service panel with a do not operate tag. A removal and install manual would have helped us to do this without incident.


Synopsis: B737 mechanic reported a failure to lock out and tag out the potable water air compressor during a valve replacement; causing the galley and cabin to flood.