Every ship has ‘bilges’ – this is space at the lowest point of the vessel between the floor of the engine room and the bottom of the ship. A water/oil mixture collects in this bilge area, where the mixture is pumped out and recovered and separated into water and oil by an on-board skimmer and demulsifying unit. The bilge de-oiling equipment is normally controlled by level switches. The oil sumps of the main engine and any auxiliary systems must also be monitored continuously for safety and environmental reasons.