What ballast water exchange methods are used?

(2) the sequential method, in which a tank or hold is first emptied by at least 95% of its volume and then refilled with ballast water; and (3) the dilution method, in which replacement ballast water is filled from the top of the tank or hold while simultaneous discharge occurs from the bottom to maintain a constant water level. Using the flow-through method or dilution method, at least three times the tank or hold volume must be pumped through.