The quality of bilge waters collected in the machinery space during normal conditions and difficulties with the bilge water systems have been considered. Analyzed systems concern contemporary cargo vessels in which the reciprocating diesel engines constitute the ships propulsion. The proposal of the bilge water system, as part of the existing bilge water installations, has been presented. That system will increase the bilge water efficiency that is pumped out overboard of the ship, decreasing the number of the international law violations. More over the proposed bilge water system can lead to decreasing the operational ships costs and raise the operational effectiveness of the engineers department