Reading a 2007 essay by Martine Acerra on the technology of slave ships in les Cahiers des Anneaux has me looking up bilge pumps. From the National Park Service and written by Courtney Andersen in 2014:
“Pumps were the last defense, hope, and salvation of the lives on board. A ship could lose its rig or its rudder, and still give a hope of survival, but without a working bilge pump a ship was lost.
The 18th century naval architect William Hutchinson observed that crews sometimes left ships too soon; that the ship may appear in imminent danger of foundering but was discovered hours or days later to be still afloat. After the water rises high enough to cover a leak, the rate of inflow is reduced; equilibrium is reached, and the ship often won’t go down much further, making it possible for the crew to pump and plug the leak.
With usually one or two “heads” aboard a ship, and sometimes hundreds of sailors, many sailors used the bilge as a latrine. The accumulation of filth and garbage in the hold polluted the bilges, and though a health hazard, the nature of the bilge water provided proof of whether the hull was tight:
Boteler 1634: “when it stinketh much, it is a sign that the water hath lain long in the hold of the ship; and on the contrary, when it is clear and sweet, it is a token that it comes freshly in from the sea. This stinking water therefore is always a welcome perfume to an old seaman; and he that stops his nose at it is laughed at, and held but a fresh-water man at best…”