D. Clear Blockage in Drain Line
(1)
Blockages in waste water drain lines may be cleared using one (or more) of the following methods. The method used depends upon the availability of resources at the operator's station and the suspected severity of blockage. Methods 2, 3 or 4 are suitable for lines that are lightly blocked and method 5 is recommended for heavily blocked lines.
(2)
Method 1
(a) If blockage is located in galley drain line with drain line strainer installed below sink, remove and check strainer. Also check drain line between strainer and sink drain fitting. If OK, proceed with method 2, 3, 4 or 5 as applicable using drain tube below strainer as point of origin in lieu of sink drain fitting. Do not apply water under pressure, insert "snake", or introduce alkaline detergent to sink drain on sinks equipped with drain line strainer.
(3)
Method 2
(a) Apply water under pressure (do not exceed 35 psi) at origin of drain line. Ensure that any connecting drains are plugged to avoid flooding during application of pressurized water.
(4)
Method 3
(a) Insert flexible revolving cable (snake). Take care at sharp bends to avoid damage to connections; do not force, work "snake" past bend by using back and forth motion.
(5)
Method 4
(a) If line is slow in draining, fill and flush with alkaline detergent.
(6)
Method 5
(a) Remove drain line sections which are suspected to contain blockage per steps below. The first elbow fitting below sink, the lines in the vicinity of drain mast, and the "Y" sections where the lateral drain lines join the longitudinal drain lines are the most common trouble areas. 1) For blocked section with ribbon heater installed, open applicable waste line
heater circuit breaker and disconnect or remove heater as necessary (Ref 30-
71-11). 2) Remove drain line fasteners, clamps and drain line section. 3) Remove blockage by blowing out with air and flush with alkaline detergent. 4) Reinstall drain line section, drain line heater (Ref 30-71-11), and drain line
strainer as applicable.
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WASTE WATER DRAIN MAST AND HEATER - REMOVAL/INSTALLATION
EFFECTIVITY
Airplanes with Drain Masts
1. General
A. Installation of drain mast requires sealing and fairing to reduce air drag.
B. The procedure for the forward or aft drain mast is identical except access.
2. Equipment and Materials
A. Permacel 2650 Silicone Rubber Tape, Permacel 421 Teflon Tape
B. BMS 5-79 Class D - Sealant (Ref 20-30-11)
C. BMS 5-95 Class B - Sealant (Ref 20-30-11)
3. Remove Drain Mast and Heater
A. Remove Drain Mast
(1)
Open all DRAIN MAST HEATER circuit breakers on P18.
(2)
Access drain mast.
(a)
For aft drain mast, remove aft cargo compartment rear bulkhead access panel (Ref Chapter 25, Cargo Compartment Bulkhead Lining).
NOTE: Drain mast is 4-1/2 feet behind bulkhead.
(b)
For forward drain mast, drain mast is on LH air conditioning fairing panel.
(3)
Remove insulation blanket away from drain mast.
(4)
Loosen fitting and disconnect drain mast tube.
(5)
Disconnect electrical wires at splices.
(6)
Remove fasteners.
CAUTION: WHEN REMOVING FASTENERS, HOLD DRAIN MAST TO PREVENT IT FROM FALLING.
(7)
Remove drain mast.
(8)
Remove and clean aerodynamic smoother and faying surface seal (Ref Chapter 51, Seals and Sealing).
B. Remove Drain Mast Heater (Aft Drain Mast Only)
(1)
Remove aerodynamic smoother.
(2)
Remove drain mast connecting fasteners.
(3)
Separate drain mast halves.
(4)
Remove heater and tube assembly.
(5)
Clean remaining aerodynamic smoother from mast halves.
Feb 20/85 38-31-21 Page 401
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
F90988
Drain Mast and Heat Installation 507
38-31-21Page 402 Figure 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 20/85
4. Install Heater and Drain Mast
A. Install Heater on Drain Mast (Aft Drain Mast Only)
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