5.3.4 Bilge Piping System – General
5.3.4(a) Bilge manifolds and valves. Bilge manifolds and valves in connection with bilge pumping are to be located in positions which are accessible at all times for maintenance under ordinary operating conditions. All valves at the manifold controlling bilge suctions from the various compartments are to be of the stop-check type. In lieu of a stop-check valve, a stop valve and a non-return valve may be accepted. If valves are fitted at the open ends of pipes, they are to be of the non-return type.
5.3.4(b) Main control valves. Where a bilge pump is connected for bilge, ballast and other sea water services, the bilge suction main, the ballast suction main, etc. are each to be provided with a stop valve, so that when the pump is used for one service, the other services can be isolated.
5.3.4(c) Bilge piping passing through tanks. Where passing through deep tanks, unless being led through a pipe tunnel, bilge suction lines are to be of steel having a thickness at least as required by column D of 4-6-2/Table 4. Pipes of other materials having dimensions properly accounting for corrosion and mechanical strength may be accepted. The number of joints in these lines is to be kept to a minimum. Pipe joints are to be welded or heavy flanged (e.g., one pressure rating higher). The line within the tank is to be installed with expansion bends. Slip joints are not permitted. A non-return valve is to be fitted at the open end of the bilge line. The purpose of this requirement is to protect the space served by the bilge line from being flooded by liquid from the deep tank in the event of a leak in the bilge line.