737 MAX Flight Crew Operations Manual
Supplementary Procedures -
Airplane General, Emer. Equip.,
Doors, Windows
SP.1.4
MN-FLT-OH-201
Water System Draining
Lavatory water supply selector valves .........................SUPPLY/DRAIN
Galley water supply shutoff valves ..................................... SUPPLY ON
The shutoff valve is found adjacent to each wet galley sink.
Drain line...............................................................Connect to drain ports
• below the main passenger entry door
• aft of the water service panel
Water service panel ..........................................................................Open
Tank drain valve handle .................................................................OPEN
Drains potable water tank and water system aft of the wings.
Forward lavatory drain valve .........................................................OPEN
Drain valve is found below the sink in the forward lavatory only.
Drain valves for coffee maker and
water boiler (if installed) ................................................................OPEN
All galley and lavatory water faucets ...............................................Open
Close faucets when water flow stops.
Accomplish the following items after verifying the potable water system
is empty:
Drain valves for coffee maker and
water boiler (if installed)................................................ CLOSED
Forward lavatory drain valve ......................................... CLOSED
Tank drain valve handle ................................................. CLOSED
Water service panel ...............................................................Close
Drain line ..........................................Disconnect from drain ports
If the potable water tank will not be refilled immediately after the system
is emptied, open the following circuit breakers and attach
DO–NOT–CLOSE tags:
P18–3 circuit breaker panel
• LAVATORY WATER HEATER A
• LAVATORY WATER HEATER D
• LAVATORY WATER HEATER E
March 1, 2021