1.8 Bilge and ballast The basic philosophy is similar in all three cases but Solas 74 only defines bilge pump capacity for passenger ships and the Convention only applies to vessels trading internationally; more over it excludes cargo ships of less than 500 gross tons. The Classification Societies generally rescribe the bore of the main bilge line and branch bilge lines and relate the bilge pump capacity of each pump to that required to maintain a minimum water speed in the line the fire pump capacity is related to the capacity of the bilge pump thus defined e. g1.8 Bilge and ballast • The basic philosophy is similar in all three cases but SOLAS 74 only defines bilge pump capacity for passenger ships and the Convention only applies to vessels trading internationally; more￾over it excludes cargo ships of less than 500 gross tons. The Classification Societies generally prescribe the bore of the main bilge line and branch bilge lines and relate the bilge pump capacity of each pump to that required to maintain a minimum water speed in the line; the fire pump capacity is related to the capacity of the bilge pump thus defined e.g