Installation of the Depressurization Valve

TASK 38-42-44-400-001-A
Installation of the Depressurization Valve

FIN: 4MD ** ON A/C NOT FOR ALL

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
172AR
161DW

B. Referenced Information

REFERENCE	DESIGNATION
TASK 12-15-38-613-001-A	Fill the Potable Water Tank System (Aircraft Electrical Power Available)
TASK 24-42-00-861-001-A	Energize the Ground Service Network from the External Power
TASK 24-42-00-862-001-A	De-energize the Ground Service Network Supplied from the External Power
TASK 25-55-12-400-001-A	Installation of the Aft Cargo-Compartment Partition at FR65
TASK 38-10-00-614-001-A	Pressurization of the Potable Water System from a Ground Air Supply
TASK 38-10-00-614-002-A	Depressurization of the Potable Water System
TASK 52-30-00-860-002-A	Close the FWD or Aft Cargo-Compartment Door with the Yellow Electric Pump
Depressurization Valve 4MD ** ON A/C NOT FOR ALL
Depressurization Valve 4MD ** ON A/C NOT FOR ALL

3. Job Set-up
Subtask 38-42-44-860-051-A ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the ground service network is energized (Ref. AMM TASK 24-42-00-861-001).
(2) Make sure that the potable water system is depressurized (Ref. AMM TASK 38-10-00-614-002).

Subtask 38-42-44-865-057-A ** ON A/C NOT FOR ALL

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
2000VU	WATER SYSTEM-DEPRESS	1MD	B02
** ON A/C NOT FOR ALL
2001VU	WATER-SYSTEM-DEPRESS	1MD	F03
** ON A/C NOT FOR ALL
2001VU	WATER SYS-AIR-COMPRESSOR	19MD	F01
** ON A/C NOT FOR ALL
2001VU	WATER-SYSTEM-DEPRESS	1MD	D05

4. Procedure
Subtask 38-42-44-420-050-A ** ON A/C NOT FOR ALL

A. Installation of the Depressurization Valve 4MD
(1) Remove the blanking plug and caps.
(2) Put the depressurization valve (4) in position and install the bolts (3), the washers (2) and the nuts (1).
(3) Connect the connection (5).
(4) Make sure that all the electrical connections are clean and in the correct condition.
(5) Connect the electrical connector 4MD-A (6).

Subtask 38-42-44-420-050-C ** ON A/C NOT FOR ALL

A. Installation of the Depressurization Valve 4MD
(1) Remove the blanking plug and caps.
(2) Put the depressurization valve (2) in position and install the bolts (3), the washers (4) and the nuts (5).
(3) Connect the connection (6).
(4) Make sure that all the electrical connections are clean and in the correct condition.
(5) Connect the electrical connector 4MD-A (1).

Subtask 38-42-44-865-058-A ** ON A/C NOT FOR ALL

B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
2000VU	WATER SYSTEM-DEPRESS	1MD	B02
** ON A/C NOT FOR ALL
2001VU	WATER-SYSTEM-DEPRESS	1MD	F03
** ON A/C NOT FOR ALL
2001VU	WATER SYS-AIR-COMPRESSOR	19MD	F01
** ON A/C NOT FOR ALL
2001VU	WATER-SYSTEM-DEPRESS	1MD	D05

Subtask 38-42-44-860-050-A ** ON A/C NOT FOR ALL

C. Preparation for Test
(1) If necessary fill the potable water system (Ref. AMM TASK 12-15-38-613-001).
(2) Make sure that the waste service panel 172AR is closed.
(3) Pressurize the potable water system (Ref. AMM TASK 38-10-00-614-001).
(4) Make sure that the work area is clean and clear of tools and other items.

Subtask 38-42-44-710-050-A ** ON A/C NOT FOR ALL

D. Do this Test.

ACTION	RESULT
1.In the lavatory/galley: operate the water faucet.	In the lavatory/galley: water flows from the water faucet.
2.At the panel 124RH: push the membrane switch 'WATER SYS DEPRESS'.	In the potable water system: the depressurization valve 4MD opens.
	At the panel 124RH: the light in the membrane switch 'WATER SYS DEPRESS' comes on after 5 s.
3.In the lavatories/galleys: after approximately 1 min operate the water faucets.	In the lavatories/galleys: water does not flow from the water faucets.
	At the panel 124RH: the lavatory 'SYSTEM INOP' light is on.
	In the lavatories: the light on the water heaters is off.
4.At the panel 124RH: push the membrane switch 'WATER SYS DEPRESS' again.	In the potable water system: the depressurization valve 4MD closes.
	At the panel 124RH: the light in the membrane switch 'WATER SYS DEPRESS' goes off.
	In the lavatories: the light on the water heaters comes on.
	At the panel 124RH: the lavatory 'SYSTEM INOP' light goes off.

Subtask 38-42-44-710-050-C ** ON A/C NOT FOR ALL

D. Do this Test.

ACTION	RESULT
1.In the lavatory/galley: operate the water faucet.	In the lavatory/galley: water flows from the water faucet.
2.At the FAP 120RH: push the 'WATER DEPRESS' push button.	At the FAP 120RH: the green light in the 'WATER DEPRESS' push button is on. the message on the aircraft symbol shows 'NO WATER PRESSURE'. at the list box the message 'VACUUM SYSTEM DISABLE - WATER DEPRESS ACTIVE' is on.
	In the potable water system: the depressurization valve 4MD is opened.
3.In the lavatories/galleys: after approximately 1 min operate the water faucets.	In the lavatories/galleys: water does not flow from the water faucets.
4.At the FAP 120RH: push the 'WATER DEPRESS' push button switch again to return the system to normal.	At the FAP 120RH: the green light in the 'WATER DEPRESS' push button switch goes off. the message 'NO WATER PRESSURE' at the aircraft symbol is off. the message in the list box is not shown.
	In the potable water system: the depressurization valve 4MD is closed.

5. Close-up
Subtask 38-42-44-410-050-A ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the access panel 131PW.
(3) Close the FWD cargo-compartment door (Ref. AMM TASK 52-30-00-860-002).
(4) Remove the access platform(s).

Subtask 38-42-44-410-050-C ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install access panel 161DW (Ref. AMM TASK 25-55-12-400-001).
(3) Close the AFT cargo-compartment door (Ref. AMM TASK 52-30-00-860-002).
(4) Remove the access platform(s).

Subtask 38-42-44-862-050-A ** ON A/C NOT FOR ALL

B. De-energize the ground service network (Ref. AMM TASK 24-42-00-862-001).

[Rev.10 from 2021] 2026.04.02 07:19:44 UTC