(2)
Forward LAV WATER HEATER

B. Depressurize water system (AMM 38-41-0/201).
C. OPEN faucet in lavatory to release pressure and to drain some of the water from the line.
D. Position primary drain valve handle to OFF.
E. Using rags to catch water in the tubes, loosen B-nuts on the tubes to the secondary drain valve.
F. Remove screws from the drain valve bracket.
G. Remove drain valve handle, loosen jut, and remove bracket.
H. Remove drain valve.
2. Install Secondary Drain Valve (Fig. 401)
A. Install drain valve.
B. Install bracket, tighten nut, and install drain valve handle.
C. Install screws to drain valve bracket.
D. Install and tighten B-nut on the tubes to drain valve.
3. Secondary Drain Valve Leak Test
A. Pressure water system (AMM 38-41-0/201).
B. Position the primary drain valve handle to DRAIN.
NOTE:  For test purposes, the primary drain valve should remain in the DRAIN. Water will not reach the secondary drain valve if the primary drain valve is in position OFF or ON.
C. OPEN the secondary drain valve, check for leaks.
D. CLOSE the secondary drain valve, check for leaks.
4. Return System to Normal
A. CLOSE circuit breakers on P18
(1)
WATER QTY IND

(2)
Forward Lavatory Water Heater

B. Position the primary drain valve handle to the ON position.
May 01/00 38-11-41 Page 401
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

K44394
Lavatory Water Drain Installation  500 
38-11-41  Figure 401  May 01/00 
Page 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

WATER TANK DRAIN VALVE - REMOVAL/INSTALLATION
1.  Prepare for Removal
A.  Drain water tank by opening fill and overflow valve and drain valve.
B.  Depressurize water tank. Refer to 38-41-0, Water Tank Pressurization System - Maintenance Practices.
C.  Close drain valve and fill and overflow valve.
D.  Open WATER QTY IND circuit breaker on panel P18.
E.  Remove aft cargo compartment rear bulkhead access panel (Fig. 401).
2.  Remove Drain Valve
A.  Obtain access through insulation blanket, attached with Velcro tape.
B.  Disconnect drain line from drain valve.
C.  Remove adapter connecting pin and two washers, and pull valve actuator shaft handle on water service panel to disconnect shaft and coupling from adapter.
D.  Remove adapter mounting screw, washer, and adapter.
E.  Loosen jamnut and remove valve.
F.  Remove O-ring and jamnut from valve.
3.  Install Drain Valve
A.  Install jamnut on valve.
B.  Install O-ring in groove on valve.
C.  Install valve on tank boss and tighten jamnut.
506 
Jul 15/70  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  38-11-51 Page 401 

F90614
Water Tank Drain Valve Installation  500 
38-11-51Page 402   Figure 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/69 

D. Attach adapter to valve with adapter mounting screw and washer.
E. Connect valve actuator shaft coupling to adapter with connecting pin and washers.
NOTE:  Install adapter connecting pin from forward end (valve closed), with shaft handle in closed position, as shown on Fig. 401.
F. Connect drain line to valve.
G. Fill passenger water tank (Ref 12-14-0).
H. Provide electrical power.
I. Pressurize water tank (Ref 38-41-0, Maintenance Practices).
J. Allow 2 minutes for pressure to stabilize.
K. Open drain valve until water starts flowing, then close valve.
L. Check valve for leaks.
4. Restore Airplane to Normal
A. Reinstall insulation blanket.
B. Replace access panel.
C. If no longer needed, remove electrical power.
Nov 15/72 38-11-51 Page 403 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

WATER HEATER – TROUBLE SHOOTING
1. Water Heater Trouble Shooting Chart

T54478 T54479
500 
Aug 15/77  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  38-11-61 Page 101 

500 
38-11-61 Page 102  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/77 

WATER HEATER - REMOVAL/INSTALLATION
1. Remove Water Heater
A. Open applicable LAVATORY WATER HEATER circuit breaker on panel P18-4.
B. Open sink cabinet disposal compartment door.
　
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