However, no branch suction pipe needs to be more than 100 mm (4 in.) internal diameter, nor is to be less than 50 mm (2 in.) internal diameter, except that for pumping out small pockets or spaces, 38 mm (1.5 in.) internal diameter pipe may be used.
5.5.1(e) Enclosed cargo space on bulkhead deck. For calculating the bilge main diameter of vessels having enclosed cargo spaces on the bulkhead deck or the freeboard deck, which is drained inboard by gravity in accordance with 4-6-4/3.5.2 and which extends for the full length of the vessel, D is to be measured to the next deck above the bulkhead or freeboard deck. Where the enclosed cargo space covers a lesser length, D is to be taken as a molded depth to the freeboard deck plus h/L, where and h are aggregate length and height, respectively, of the enclosed cargo space.
5.5.1(f) Bilge common-main. The diameter of each common-main bilge line may be determined by the equation for bilge branches given in 4-6-4/5.5.1(d) using the combined compartment length upstream of the point where the diameter is being determined. In case of double hull construction with full depth wing tanks served by a ballast system, where the beam of the vessel is not representative of the breadth of the compartment, B, may be appropriately modified to the breath of the compartment. However, no common-main bilge pipe needs to be more than the diameter for the bilge main given in 4-6-4/5.5.1(a).