Section 25(3)(d) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(d)Piping serving such wells if installed within the double bottom shall be fitted with valves or other closing arrangements located at the point of connection to the tank served to prevent oil outflow in the event of damage to the piping. Such piping shall be installed as high from the bottom shell as possible and these valves shall be kept closed at sea at any time when the tank contains oil cargo, except that they maybe opened only for cargo transfer needed for the purpose of trimming of the ship.