15.—(1) The number of sidescuttles, scuppers, sanitary discharges and other openings in the shell below the bulkhead deck shall be the minimum which is compatible with the design and proper working of the ship.
(2) The arrangements for closing every such opening below the bulkhead deck shall be consistent with its intended purpose and shall be such as will ensure watertightness.
(3) The design and arrangements of openings in the shell plating below the margin line shall be in accordance with the specifications set out in Schedule 10 in Merchant Shipping Notice MSN 1698 (M).
(4) (a) In all ro-ro passenger ships, scuppers shall be fitted in special category spaces so as to ensure that water which may otherwise accumulate by operation of the fixed pressure water-spraying system is rapidly discharged directly overboard.
(b)In all ro-ro passenger ships, discharge valves for scuppers leading from special category spaces which are fitted with positive means of closing operable from a position above the bulkhead, in accordance with regulation 15(3), shall be kept open when the ship is at sea.