MARPOL discharge checker

The International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) regulates discharges from vessels across six Annexes. This tool covers the four most operationally relevant Annexes for deck and engine officers:

Annex I — Oil: oily bilge water, oily mixtures from cargo areas of tankers.
Annex II — Noxious Liquid Substances (NLS): Categories X, Y, Z.
Annex IV — Sewage: treated and untreated.
Annex V — Garbage: all categories A–I including plastics, food waste, cargo residues.

Annex VI governs air emissions (sulphur, NOx). For ECA fuel sulphur requirements use the ECA checker.

Study aid only. Always consult the ship's SOPEP, SMPEP, Garbage Management Plan, and flag-state circulars. Conditions in Special Areas and flag-state stricter requirements may apply.

Cargo / waste typeMARPOL zoneDistance from nearest land (NM)Vessel speed (knots)

PERMITTED with restrictions

Permitted in open sea ≥ 12 nm from nearest land, vessel underway ≥ 7 kt, rate ≤ 60 L/NM, OWS fitted, ORB entry required, oil content ≤ 15 ppm.

MARPOL Annex I, Reg 15(1)–(4)

Decision tree covers MARPOL Annex I (oil), Annex II (NLS), Annex IV (sewage), Annex V (garbage). Annex VI (air) governs fuel sulphur and NOx in ECAs — see ECA Checker tool. Always consult the ship's SOPEP, SMS, and flag-state circular for vessel-specific requirements.

Embed this tool on your site

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When to use this tool

Before any operational discharge decision — bilge water, oily mixtures, sewage, garbage, tank cleaning slop. Also for training + STCW refresher preparation. NOT authoritative for a live decision — always cross-check against the ship's SOPEP/SMPEP + Garbage Management Plan + flag-state circulars.

Worked example

Scenario: Panamax bulker at 65°N, 15°W (North Sea SOx ECA). Chief Engineer needs to discharge processed bilge water via 15 ppm oily-water separator.

Check: Position → NOT in a MARPOL Annex I Special Area (Baltic + Med + NW European Waters are; the North Sea itself is only a SOx ECA under Annex VI, distinct from Annex I Special Area status). Distance from land > 12 nm. Speed > 4 kn. OWS at 15 ppm. → Discharge permitted subject to Oil Record Book Part I entry code C.

Interpretation: Comply with all four conditions + record. Note the distinction between Annex I and Annex VI Special Areas — different geographic scopes.

Regulatory basis

MARPOL Annex I (oil) Regulations 15 + 34, Annex II (NLS) Reg 13, Annex IV (sewage) Reg 11, Annex V (garbage) Reg 4-6. Special Areas listed in each Annex. Enforced via PSC MoU regimes + flag-state oversight per III Code. Any violation is typically a Category 1 PSC finding and can trigger criminal prosecution under flag + port state law (e.g. US CFR 33 + EU Ship-Source Pollution Directive).