Slop Tank

A slop tank collects the oily residues, tank washings, and dirty ballast generated by an oil tanker, letting oil and water separate so the cleaned water can be decanted within the MARPOL Annex I discharge limits. Annex I Regulation 29 requires slop tank arrangements of adequate capacity on tankers of 150 GT and above, sized to the cargo and the load-on-top method. Discharge from the slop tank is controlled through the ODMCS to the Regulation 34 limits, with the oil retained on board for delivery to a reception facility. Slop tanks are central to crude oil washing and the load-on-top practice.