(b)  
Remove the drain line strainer if it is installed (Ref 25-31-13/401).

 (c)  
Do a check of the drain line strainer to make sure it is clean and there is no damage.

 (d)  
Clean the drain line strainer (AMM 25-31-13/701).

 (e)  
Do a check of the drain line for blockage between the strainer and the sink drain fitting.

 (f)  
If the top drain between the strainer and the sink drain is clear, continue with steps 2.F.(1) thru 2.I.(3), as applicable, to remove the blockage.

 (g)  
Use the drain line below the drain line strainer as the start point to remove the blockage from the clogged drain line.

 F. Remove the Blockage From the Drain lines That are Lightly Blocked
 S 112-004
 WARNING: OBEY THE VENDOR SAFETY PROCEDURES FOR THE ALKALINE
_______
 CLEANER. CONTACT WITH THE SKIN OR EYES MAY CAUSE
 IRRITATION OR BURNS.

 WARNING:_______MAKE SURE THE WATER PRESSURE IS NOT MORE THAN 25 PSI. WATER PRESSURE MORE THAN 25 PSI CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
 CAUTION: DO NOT PRESSURIZE THE WATER ON DRAIN LINES WITH A DRAIN LINE
_______ STRAINER INSTALLED. DO NOT PUT A FLEXIBLE SHAFT (SNAKE) OR ALKALINE DETERGENT INTO THE DRAIN ON THE SINKS WITH A DRAIN LINE STRAINER INSTALLED. DAMAGE TO EQUIPMENT CAN OCCUR.
 (1)  Fill the drain lines that are slow to drain with an alkaline detergent.
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747-400 MAINTENANCE MANUAL
 S 142-005
 (2)  If the drain becomes clear, continue with step 2.I.(1).
 NOTE: Make sure the drain inlets that connect to the drain line are
____ sealed with plugs. This is to prevent the flow of water from the drain when you pressurize the water.
 S 142-006
 (3)  
Pressurize the water at the drain connection.

 S 142-007

 (4)  
If the drain line becomes clear, continue with step 2.I.(1).

 S 142-008
 CAUTION: DO NOT USE FORCE WITH THE FLEXIBLE SHAFT (SNAKE) AROUND A SHARP
_______
 BEND OR CURVE IN THE DRAIN LINE. DAMAGE TO THE DRAIN
 CONNECTIONS CAN OCCUR.

 (5)
Push and slowly turn a flexible shaft (snake) into the drain line.

 S 412-009

 (6)  
If the drain line becomes clear, continue with step 2.I.(1).

 G. Remove the Blockage From the Heavily Blocked Drain Lines
 NOTE: You must remove parts of the drain lines for heavily blocked
____ drains. The parts that cause the most problems are found in these locations:
 -
The first elbow fitting below the sink

 -
The fittings near the drain mast

 -
The Y sections where the lateral drain lines join the longitudinal drain lines.

 S 032-010
 (1)  
Disconnect and remove the drain line heaters from the drain lines, if it is applicable (AMM 30-71-01/401).

 (2)  
Remove the drain line fasteners and clamps.

 (3)  
Remove the drain line.

 (4)  
Remove the blockage from the drain line with compressed air.

 S 032-011
 S 022-021
 S 142-012
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. FREIGHTERS ú

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 152-013
 (5)  
Flush the drain line with an alkaline detergent.

 S 152-014

 (6)  
Flush the drain line with clean water.

 H. Install the Drain Line
 S 422-015
 (1)  
Put the drain line into its position.

 S 412-016

 (2)  
Install the drain line fasteners and clamps.

 S 432-017

 (3)  
Install the drain line heater, if it is applicable
　
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