pumping system is used to remove water from a ship's
. This is important, as water in the hull is a leading cause of sinking
(hmm...) Bilge pumps have a capacity ranging from 2500 GPH
per hour) for a small sailboat
, to 10,000 GPH or more for a larger 50-60ft boat.
Bilge pumps may be manually activated, or set to trigger at a certain water level. It's generally a good idea to have a bilge pump in each hull compartment that has no free flow of water to another compartment (i.e., may fill up with water and weigh the boat down).
Information from David H. Pascoe's writing on the subject at http://marinesurvey.com/yacht/bilge_pumps.htm