The APU bleed air check valve and the unloader check valve do not let pressure from one source go to the other source.
The compressor inlet air filter and the in-line air filter remove particles from the air.
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777 AIRCRAFT MAINTENANCE MANUAL

WATER TANK PRESSURIZATION -INTRODUCTION

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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -1

Component Locations
These components are behind the end wall of the bulk cargo compartment:
*
Pressure relief valve

*
Pressure limit switch.

These components are above the ceiling panels in the aft section of the bulk cargo compartment.
*
Pressure regulator

*
APU bleed air check valve

*
In-line air filter

*
Unloader check valve.

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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -1

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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -2 Compressor and Pneumatic Drain Valve Location
The air compressor is behind the panels on the right side of the bulk cargo compartment.
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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -2

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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -3

Compressor Interlock Switch Location
The compressor interlock switch is on the fill/overflow valve. The valve is behind the right end wall of the bulk cargo compartment.
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WATER TANK PRESSURIZATION -COMPONENT LOCATIONS -3

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WATER TANK PRESSURIZATION -AIR COMPRESSOR

Purpose
The potable water air compressor pressurizes the potable water tanks.
Physical Description
The air compressor has these parts:
*
Compressor inlet air filter

*
Electrical connector

*
Motor

*
Compressor.

Location
The compressor is on the right side of the bulk cargo compartment. It is behind the potable water air compressor panel.
Functional Description
The three-phase motor operates the compressor to pressurize the potable water tanks. The motor starts when tank pressure is less than 35 psig. The motor stops when tank pressure is 45 psig. The motor also stops when the preselect overflow valve is in the open position.
Three switches protect the motor when it becomes too hot or has too much current. There is a switch for each phase of the motor. These switches automatically go back to the normal position when they cool.
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WATER TANK PRESSURIZATION -AIR COMPRESSOR

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WATER TANK PRESSURIZATION -COMPRESSOR INLET AIR FILTER

Purpose
The compressor inlet air filter removes particles from the air before it goes into the potable water air compressor.
Physical Description
The air filter is a one piece, canister that mounts with an o-ring.
Location
The air filter attaches to the air compressor. It is on the forward side of the compressor.
Training Information Point
The filter is replaceable.
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WATER TANK PRESSURIZATION -COMPRESSOR INLET AIR FILTER

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WATER TANK PRESSURIZATION -APU BLEED AIR CHECK VALVE

Purpose
The APU bleed air check valve does not permit pressure from the compressor to pressurize the pneumatic duct.
Location
The check valve is above the ceiling in the aft section of the bulk cargo compartment. It is above and forward of the inboard water tank. It is in the pressure line from the pneumatic system, upstream of the air filter.
Training Information Point
The check valve has a flow direction arrow. You must install this valve with the arrow in the direction of the flow. If you install the valve incorrectly, the system will fail a functional test. Incorrect installation does not permit the pneumatic system to pressurize the water tanks.
　
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