Technician reported that proper procedure was not followed when a drain mast was repaired.

Attributes
ACN	1724332
Time
Date	202002
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Component
Aircraft Component	Drinkable/Waste Water Syst
Person 1
Function	Technician
Qualification	Maintenance Powerplant Maintenance Airframe
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural MEL Deviation - Procedural Published Material / Policy

Narrative:

Aft drain mast was removed in ZZZ. Was reinspecting tape and realized no blanking plate had been installed. Tape was blown out from inside. Contacted engineering was told the blanking plate was not required because drain mast was going to reinstalled so that step from amm is not necessary. I do not believe that is the proper interpretation of the amm.

Original NASA ASRS Text

Title: Technician reported that proper procedure was not followed when a drain mast was repaired.

Narrative: Aft drain mast was removed in ZZZ. Was reinspecting tape and realized no blanking plate had been installed. Tape was blown out from inside. Contacted engineering was told the blanking plate was not required because drain mast was going to reinstalled so that step from amm is not necessary. I do not believe that is the proper interpretation of the AMM.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.