(2)
An alternate way of pressurizing the water tank is by connecting a pressure source to the air valve on the water service panel.
(3)
The water tank must be depressurized prior to performing maintenance on any part of the potable water system.
WARNING: MAKE SURE POTABLE WATER SYSTEM IS DEPRESSURIZED. HIGH PRESSURE/TEMPERATURE AIR CAN BE DANGEROUS TO PERSONNEL.
(a)
For lavatory components: 1) Prior to maintenance, turn the lavatory 3-way drain valve to the CLOSED
position. 2) After maintenance, turn the valve to the ON position.
(b)
For water tank and all components of the water tank pressurization system: 1) Prior to maintenance, depressurize water tank per step B below. 2) After maintenance, pressurize water tank per step C below.
(c)
For all other components of the potable water system:
1) Prior to maintenance: a) Gravity drain the potable water system (Ref 38-11-0, Servicing). b) Ensure that the water tank drain valve is in the OPEN position. c) Ensure that the fill and overflow valve is in the OPEN position.
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2) After maintenance, fill the water tank (Ref Chapter 12, Water System -Servicing).
B. Depressurize Water Tank
(1)
If operating, shut down No. 1 engine (Ref Chapter 71, Power Plant - Operating
Procedure).
(2)
If No. 2 engine is operating, close Bleed Air Isolation Valve (Ref Chapter 36, Engine Bleed Air System - Operating Procedure).
(3)
If operating, shut down APU (Ref Chapter 49, APU Power Plant - Operating Procedure).
(4)
If connected, disconnect ground pneumatic card from pneumatic manifold connector.
(5)
Momentarily turn left and right air conditioning pack valve switches on forward overhead panel to ON, then turn to OFF.
(6)
If connected, disconnect air pressure source from air valve at water service panel.
(7)
Open fill and overflow valve, then close.
(8)
If it is desired to pressurize the pneumatic manifold while performing maintenance in the water system, disconnect the water tank pressurization line as follows:
(a)
Depressurize both systems by performing steps 1.B.(1) thru .B.(7).
WARNING: IF PRESSURE LINE IS DISCONNECTED BEFORE DEPRESSURIZING, HIGH PRESSURE/TEMPERATURE AIR IN THE LINE MAY CAUSE INJURY TO PERSONNEL.
(b)
Open A/C access panel 3303 (Ref Chapter 12, Access Doors and Panels).
(c)
Disconnect water tank pressurization line at plugged tee about 20 inches aft of air cycle machine. Cap or plug lines.
(d)
Pressurize pneumatic manifold by using the engines, the APU, or a pneumatic ground cart.
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C. Pressurize Water Tank
(1) If water tank pressurization line has been disconnected, proceed as follows:
(a)
Depressurize pneumatic manifold by performing steps 1.B.(1) thru 1.B.(4).
(b)
Remove plugs or caps and connect water tank pressurization line.
WARNING: IF PLUGS OR CAPS ARE REMOVED WITH MANIFOLD PRESSURIZED, HIGH PRESSURE/TEMPERATURE AIR MAY CAUSE INJURY TO PERSONNEL.
(2)
Pressurize water tank in either of the following three ways:
(a)
Start APU and move APU bleed air switch on panel P6 to ON (Ref Chapter 49, Operating Procedure).
(b)
Connect ground pneumatic cart and pressurize pneumatic manifold. Check that isolation valve switch on forward overhead panel is positioned open.
(c)
Connect pressure source to air valve on water service panel and pressurize tank.
(3)
Allow 2 minutes for pressure to stabilize.
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WATER TANK PRESSURIZATION SYSTEM FILTER - SERVICING
1. Remove Water Tank Pressurization System Filter Element
A. Depressurize water tank (Ref 38-41-0, MP).
B. Remove the aft cargo compartment rear bulkhead access panel.
C. Disconnect lockwire and unscrew filter case and element from filter head (Fig. 301).
D. Remove filter element and clean filter case.
2. Install Water Tank Pressurization System Filter Element
A. Insert O-ring in filter element and place new element in filter case (Fig. 301).
B. Place O-ring on filter case and screw filter case into filter head. Torque filter case to 50 +10 pound-inches.
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