Oil and all oily mixtures must either be retained on board for subsequent discharge to reception facilities or discharged into the sea in accordance with the following provisions:
(1) the ship must be proceeding en route; (2) the ship must have in operation equipment of a design approved by the flag State Administration that ensures that the oil content of the effluent without dilution does not exceed 15 ppm: (3) the oily mixture must not originate from cargo pump room bilges on oil tankers; and (4) the oily mixture, in case of oil tankers, must not be mixed with oil cargo residues. (MARPOL Annex I, reg. 15. 6)
