Bilge Pumps for Commercial Vessels

Bilge pumps remove unwanted water (with oil residues, sludge, and small solids) from the lowest spaces of the vessel for discharge overboard or to a holding tank. Ballast pumps move large volumes of clean seawater into and out of ballast tanks to control trim, list, and draught. Bilge pumps are typically smaller, self-priming, and oil-tolerant; ballast pumps are larger, higher-flow, and handle relatively clean seawater.

Yes. Bilge pumps are usually installed above the bilge water level and must lift water through a suction line. Self-priming capability ensures the pump can evacuate air from the suction line and start pumping water without an external priming system. Typical priming lift is 6–8 metres.

Under MARPOL Annex I, oily bilge water must be processed through an oily water separator (OWS) before discharge overboard. The discharge must contain less than 15 parts per million (ppm) of oil. A 15 ppm bilge alarm continuously monitors the discharge and automatically stops overboard discharge if the limit is exceeded.

SOLAS requires at least two independent power-driven bilge pumps for cargo and passenger vessels, with capacities calculated based on the cross-sectional area of the bilge main, vessel length, and beam. One must be independently driven (separate prime mover or power source) to serve as an emergency bilge pump.

Yes, this is common practice on commercial vessels. SOLAS permits the use of a fire pump as the second independent bilge pump if it can be connected to the bilge system through suitable valves and is of adequate capacity. The arrangement must prevent cross-contamination between sea water (fire main) and bilge water.