Samo se prostor/zapremina može isprazniti (Bilge holes must be empty), stoga je "holes" upotrebljeno u smislu rupa/šupljina, a ne otvor.

"Cevovodi (sistemi) drenaže

Drenažni cevovodi služe za izbacivanje vode koja naglo prodire u brodske prostore usled oštećenja brodske konstrukcije ili se postepeno nakupi zbog malih propuštanja.

Glavna drenaža proteže se kroz sve brodske prostore, sa ograncima koji se završavaju usisnim koševima. Pomoćna ili kaljužna drenaža je slična ali manjih dimenzija, služi za izbacivanje manjih količina vode iz brodskih kaljuža (prostor na dnu brodskih prostorija, posebno u mašinskom odeljenju)."

[http://www.paluba.info/smf/index.php?topic=7393.0;wap2]

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Note added at 4 days (2014-04-29 23:12:54 GMT)
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"BILGE

The bilge (IPA: /bɪldʒ/) is the lowest compartment on a ship, below the waterline, where the two sides meet at the keel. The first known use of the word is from 1513.

Bilge water

The word is sometimes also used to describe the water that collects in this area. Water that does not drain off the side of the deck drains down through the ship into the bilge. This water may be from rough seas, rain, leaks in the hull or stuffing box, or other interior spillage. The collected water must be pumped out to prevent the bilge from becoming too full and threatening to sink the ship.

Bilge water can be found aboard almost every vessel. Depending on the ship's design and function, bilge water may contain water, oil, urine, detergents, solvents, chemicals, pitch, particles, and other materials.

By housing water in a compartment, the bilge keeps these liquids below decks, making it safer for the crew to operate the vessel and for people to move around in heavy weather."
[http://en.wikipedia.org/wiki/Bilge]