MD-11 Flight Crew Operations Manual
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Water and Waste Chapter Wat
Description and Operation Section 10
Wat.10.1
Wat.10 Water and Waste-Description and Operation
Potable Water System
Passenger
Two systems (4 tanks) supply pressurized and fresh water for the galleys, coffee
makers, drinking fountains, lavatory washstand, and toilet flush.
The tanks are installed below the cabin floor in the left and right-hand tunnel of
the forward cargo compartment. Hoses allow flexible lavatory and galley
configurations.
When the engines or APU are operating, bleed air from pneumatic systems 1 and
2 automatically pressurizes (40-45 psi) the system. If the engine or APU air
pressure drops below about 38 psi, a compressor automatically starts to maintain
normal system pressure (if electric power is available).
On the ground, when electric power and air are not available, the system can be
pressurized at the exterior service panel located on the lower fuselage near the
nose.
Waste System
Passenger
A vacuum waste system uses a pressure differential to move water and waste from
the toilets or sinks to the two waste tanks installed behind the aft cargo
compartment.
On the ground, differential pressure is supplied by blowers. Above about 16, 000
feet the blowers are deactivated since the cabin-to-ambient differential pressure is
sufficient.
The system is controlled by a dual channel Waste Control Unit (WCU). If one
channel fails, control transfers to the other channel.
The toilets are controlled by a Flush Control Unit (FCU). The FCU interfaces with
the WCU to control the toilet flush valve and rinse unit.
In the forward and mid lavatories and galleys, waste water from the water fountain
and sinks drains into the vacuum waste system. In the aft lavatories and galleys,
water from the water fountains and sinks drains overboard through a drain mast.
The exterior service panel is located on the lower fuselage near the tail.
October 02, 2006
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