3.5.2 Inboard Drains
Where the summer freeboard is such that the deck edge of the cargo space being drained is immersed when the vessel heels 5 degrees, the drains from these enclosed cargo spaces are to be led to a suitable space, or spaces, of adequate capacity, having a high water level alarm and provided with fixed pumping arrangement for discharge overboard. In addition, the system is to be designed such that: i) The number, size and disposition of the drain pipes are to prevent unreasonable accumulation of free water; ii) The pumping arrangements are to take into account the requirements for any fixed pressure water-spraying fire-extinguishing system; iii) Water contaminated with substances having flash point of 60°C (140°F) or below is not to be drained to machinery spaces or other spaces where sources of ignition may be present; and iv) Where the enclosed cargo space is protected by a fixed gas fire-extinguishing system, the drain pipes are to be fitted with means to prevent the escape of the smothering gas. The U-tube water seal arrangement should not be used due to possible evaporation of water and the difficulty in assuring its effectiveness.