A bilge pump is a water pump used to remove bilge water from a boat or ship. Electric bilge pumps are often fitted with float switches that turn the pump on when the bilge reaches a certain level. Having a backup pump is often recommended in case the primary pump fails. The primary pump is usually located at the lowest point in the bilge, whereas the secondary pump is placed higher up. This way, the secondary pump only activates if the primary pump can’t cope or fails, and it is kept clear of any debris that could clog the primary pump.

In the past, force pumps could be made from either wood or bronze, with bronze being the preferred material as it was more durable and portable. These pumps consisted of a cylinder, a piston and some valves. Water would fill the cylinder and the piston would descend, forcing the water into a higher placed pipe. A valve would close and lock the water in, sending it out in a jet stream. Force pumps were used on ships to suck in sea water for live fish tanks, to fight fires, and to get rid of excess water. On land, they were used to bring water up from wells or to fill tanks that could then be used to pressure pump water for household use or irrigation.