line/line sample

English to Italian Tech/Engineering Aerospace / Aviation / Space Aviation Fuel Tanks

Ho dei dubbi sul significato del termine "line" in questo passaggio di un testo riguardante cisterne/serbatoi di carburante da aviazione:

Storage tank and product recovery tank sumps/low points shall be checked daily for the presence of water and sediment.
Additional checks should be made when frequent or heavy rainfall occurs. Procedure is to flush at full flow a quantity in excess of the line content from the storage tank sump/low point to the sample receiving vessel, and then to take a line sample for an Appearance/Visual Check.

Io credo sia una tubatura, o conduttura, ma non ne sono sicuro.

Grazie!