MARPOL Annex IV: Sewage from Ships

MARPOL Annex IV is the annex to the International Convention for the Prevention of Pollution from Ships that controls the discharge of sewage from ships, through equipment requirements, discharge conditions, survey and certification, port reception facilities and port State control. It applies under Regulation 2.1 to ships on international voyages of 400 gross tonnage and above, and to smaller ships certified to carry more than 15 persons. The original Annex entered into force on 27 September 2003. The text in force today is the revised Annex adopted by Resolution MEPC.115(51) on 1 April 2004 and in force from 1 August 2005, as amended by seven resolutions through MEPC.274(69) of 2016.

Annex IV is an optional annex. A State that ratifies MARPOL is bound by Annex I and Annex II , but accepts Annex IV separately. The IMO Status of Treaties, Volume I, dated 30 September 2026, records 150 Contracting States. The United States is not one, and regulates vessel sewage under its own law instead.

Discharge criteria summary

The table states the Annex IV discharge conditions as amended to October 2026. Sources are Regulation 11 as replaced by MEPC.200(62) and amended by MEPC.274(69), and Polar Code Part II-A chapter 4 as made mandatory by MEPC.265(68).

In polar waters, category A and B ships and all passenger ships constructed on or after 1 January 2017 may discharge only through an approved plant (Polar Code 4.2.2). The full regulation-by-regulation treatment of the discharge regime is in the article on sewage discharge under Regulation 11 .

Structure of the Annex

Annex IV has 18 regulations in seven chapters, plus an appendix holding the form of the ISPP Certificate. Regulation numbers changed after 2005, which is why older manuals, company procedures and some class documents cite regulation numbers that no longer match the consolidated text.

The renumbering comes from MEPC.200(62). As adopted on 15 July 2011, it inserted a Regulation 12bis on passenger-ship reception facilities. The IMO Secretary-General’s correction of editorial errors, dated 27 June 2014, renumbered 12bis as Regulation 13 and the existing port State control regulation, Regulation 13, as Regulation 14, with effect from the amendments’ entry into force on 1 January 2013. The same correction renumbered definitions 5bis, 7bis and 7ter as paragraphs 6, 9 and 10 of Regulation 1. A reference to “Regulation 12bis” or “Regulation 13” for port State control is the pre-2014 numbering.

Definitions under Regulation 1

Regulation 1 holds the terms on which every other regulation turns, and two of them decide most practical disputes: what counts as sewage, and where the nearest land is. The full definition set is covered in the article on Annex IV Regulation 1 definitions .

Sewage (Regulation 1.3) has four limbs:

1. drainage and other wastes from any form of toilets and urinals;
2. drainage from medical premises (dispensary, sick bay and similar) via wash basins, wash tubs and scuppers located in such premises;
3. drainage from spaces containing living animals;
4. other waste waters when mixed with the drainages defined above.

The fourth limb is the one that pulls grey water into Annex IV. Shower, galley and laundry water is not sewage on its own; once it is routed into a tank or treatment plant that also takes toilet drainage, the mixture is sewage and Regulation 11 governs its discharge. The livestock limb means the drainage from the animal spaces of a livestock carrier is sewage, although whether the ship is subject to Annex IV still turns on its tonnage and persons on board.

Holding tank (Regulation 1.4) is a tank used for the collection and storage of sewage. Nearest land (Regulation 1.5) means the baseline from which the territorial sea is established under international law, with one exception: off the north-eastern coast of Australia, nearest land is a line drawn along the outer edge of the Great Barrier Reef between coordinates listed in the regulation. The same construction is used across the MARPOL annexes and is covered in the article on nearest land under MARPOL .

Passenger ship (Regulation 1.10) means a ship that carries more than 12 passengers, as the paragraph was replaced by MEPC.274(69). For the Baltic rule, a “new passenger ship” is one with a building contract or keel-laying on or after 1 June 2019, or delivery on or after 1 June 2021. Special area means the Baltic Sea area as defined in Annex I Regulation 1.11.2, and any other sea area designated by the Organization. Person means a member of the crew or a passenger, which matters for the 15-person threshold in Regulation 2.

MEPC.246(66) added paragraphs 12 to 15, defining the audit, the Audit Scheme, the Code for Implementation and the audit standard, for the verification chapter.

Application under Regulation 2 and exceptions under Regulation 3

Annex IV applies to ships engaged in international voyages that are of 400 GT and above, or of less than 400 GT and certified to carry more than 15 persons (Regulation 2.1). The two limbs work independently. A 300 GT expedition yacht certified for 12 guests and 8 crew is inside Annex IV because it carries 20 persons. A 3,000 GT general cargo ship with a crew of 14 is inside it because of its tonnage.

Two scope limits follow from the text:

• International voyages only. A ship that trades only within its own State’s waters is outside Regulation 2.1. Its flag State may apply equivalent rules nationally.
• Existing ships. Regulation 2.1 required existing ships to comply five years after the Annex entered into force, and Regulation 2.2 allowed existing ships keel-laid before 2 October 1983 to be equipped “as far as practicable”.

Exceptions (Regulation 3) are narrower than many company manuals state. Regulation 11 does not apply to a discharge necessary to secure the safety of the ship and those on board or to save life at sea, or to a discharge resulting from damage to the ship or its equipment where all reasonable precautions were taken before and after the damage to prevent or minimize it. Those are the only two. Since MEPC.265(68) the chapeau of Regulation 3.1 also disapplies section 4.2 of the Polar Code’s chapter 4 in the same two cases. The exceptions are covered in the article on Annex IV Regulation 3 exceptions .

A coastal State can relax the rule in its own waters. Under Regulation 11.2, the Regulation 11.1 conditions do not apply to ships operating in the waters under the jurisdiction of a State, and to visiting ships in those waters, while they discharge sewage in accordance with less stringent requirements imposed by that State. The reverse does not hold: a coastal State that wants stricter rules does so under its own law, as Canada and HELCOM do (see the regional overlays below).

Surveys and the ISPP Certificate (Regulations 4 to 8)

Every ship that Annex IV applies to and that sails to ports or offshore terminals of other Parties carries an International Sewage Pollution Prevention (ISPP) Certificate, issued under Regulation 5 after a survey under Regulation 4. The certificate records which of the three equipment options the ship has and, for a plant, the standard it was type-approved to.

Regulation 4.1 provides for three surveys only:

• an initial survey before the ship is put in service or the certificate is first issued;
• a renewal survey at intervals specified by the Administration, not exceeding five years;
• an additional survey, general or partial, after repairs or renewals.

There is no annual or intermediate survey. The Annex I IOPP Certificate, by contrast, carries both, so a survey planner that copies the IOPP pattern onto the ISPP Certificate schedules surveys the Annex does not require.

Regulation 4.8 prohibits any change to the equipment, systems, fittings, arrangements or material covered by the survey without the Administration’s sanction, except direct replacement of equipment and fittings. A plant swapped for a different model, or a comminuter replaced by a full plant, goes through an additional survey.

The other certificate rules are short:

• Regulation 6: another Party may survey and certify at the Administration’s request, but no ISPP Certificate is issued to a ship flying the flag of a State that is not a Party to Annex IV (Regulation 6.4).
• Regulation 7: the certificate follows the model form in the appendix; where it is not drawn up in English, French or Spanish, it includes a translation into one of them.
• Regulation 8: validity does not exceed five years. A certificate may be extended by up to three months to let a ship complete its voyage to the port of survey (Regulation 8.5), or by one month for ships on short voyages (Regulation 8.6). It ceases to be valid on transfer of the ship to another flag (Regulation 8.8).

Surveys are carried out by the Administration’s officers, by nominated surveyors, or by a recognized organization acting for the flag State . Some flag States go further than the Annex for small ships: the Bahamas Maritime Authority’s Marine Notice 59 lets its recognized organizations issue a Statement of Compliance on request to ships under 400 GT carrying 15 or fewer persons, which the Annex does not require. The survey cycle and certificate supplement are covered in detail in the article on ISPP Certificate surveys .

Sewage systems under Regulation 9

Regulation 9.1 requires every ship that Annex IV applies to to be fitted with one of three systems:

1. A sewage treatment plant (STP) of a type approved by the Administration, taking into account the standards and test methods developed by IMO (Regulation 9.1.1).
2. A comminuting and disinfecting system approved by the Administration, with facilities for temporary storage of sewage when the ship is less than 3 nm from the nearest land (Regulation 9.1.2).
3. A holding tank of a capacity to the Administration’s satisfaction for the retention of all sewage, having regard to the operation of the ship, the number of persons on board and other relevant factors, with a means to indicate visually the amount of its contents (Regulation 9.1.3).

Regulation 9.2, added by MEPC.200(62), applies to passenger ships to which Regulation 11.3 applies while in a special area. They may use only a type-approved plant meeting the nutrient standard (Regulation 9.2.1) or a holding tank (Regulation 9.2.2). The comminuter option is not available to them.

Annex IV says nothing about tank coatings, high-level alarms, ventilation or vent heights. Those come from class rules, from the flag State and, for gas safety, from the ISM Code safety management system. Plant types, approval and operation are covered in the article on sewage systems under Regulation 9 , and the engineering of biological, membrane and physico-chemical plants in the article on sewage and grey water treatment systems .

STP effluent standards: MEPC.227(64)

The 2012 Guidelines adopted by MEPC.227(64) on 5 October 2012 set the effluent standards and the type-approval test for plants installed on or after 1 January 2016. The standard is a recommendatory guideline. It becomes binding through Regulation 9.1.1, which requires type approval “taking into account” the IMO standards, and through the ISPP Certificate form, which names the standard the plant was approved to.

Section 4.1 sets five limits, each judged as the geometric mean of the effluent samples over the test period:

Qi/Qe is the dilution compensation factor, influent flow over effluent flow. Section 3.2 says a plant should not rely solely on dilution; where dilution water is added, the limits are scaled by Qi/Qe so the plant gains nothing by it. The coliform limit is not scaled. For the geometric mean, a zero coliform count is entered as 1 per 100 ml and a result below the detection limit as half that limit (section 4.1.5).

Disinfectant residual is handled in section 5.7 rather than as a numeric limit. Administrations are encouraged to favor ozone, ultraviolet or other disinfectants, and where chlorine is used, best technical practice should keep the residual in the effluent below 0.5 mg/l.

The test. Section 5.3 sets a minimum test period of 10 days after the plant reaches steady state. Section 5.5.1 requires a minimum of 40 effluent samples, and section 5.4.1 requires testing at minimum, average and maximum volumetric loadings. The parameters recorded are thermotolerant coliforms, TSS, BOD5, COD, pH and residual chlorine (section 5.6). The Administration issues the Certificate of Type Approval. IMO approves no test facility and no manufacturer.

Which standard applies. MEPC.227(64) runs on the plant’s installation date:

MEPC.284(70), adopted 28 October 2016, defined “installed on or after 1 January 2016” as a ship whose keel was laid or which was at a similar stage of construction on or after that date, or, for other ships, a contractual delivery date of the equipment on or after that date (the actual delivery date where there is no contractual one). It also split the type-approval certificate into two forms, one including and one excluding the section 4.2 nutrient standard, and deleted paragraphs 4.4 and 4.5. It changed no effluent limit.

A plant approved to an earlier standard does not have to be replaced when a ship changes trade, with one exception. It stays approved to the standard in force when it was installed, which is the standard stated in item 1.1 of the ISPP Certificate. The exception is a passenger ship entering the Baltic Sea Special Area: under Regulations 9.2 and 11.3 it needs a plant certified to the section 4.2 nutrient standard, or it holds all sewage while in the special area. The test protocol and the certificate wording are covered in the article on the MEPC.227(64) sewage treatment plant standard .

Holding tanks

Annex IV sets no holding-tank volume. Regulation 9.1.3 leaves capacity to the Administration, “having regard to the operation of the ship, the number of persons on board and other relevant factors”, and requires only a visual contents indicator. The calculation and the assumptions flag Administrations accept are worked through in the article on holding tank sizing .

Holding tanks produce hydrogen sulfide as sewage turns septic, so the tank is an enclosed space for entry purposes. Entry is governed by the company’s enclosed space entry procedure, with the portable atmosphere-testing instrument that SOLAS Regulation XI-1/7 requires ships to carry, not by Annex IV.

Standard discharge connection under Regulation 10

Regulation 10.1 fixes the dimensions of the flange on the ship’s sewage discharge pipeline so that any ship can connect to any shore reception hose. The pipeline is led to the outside of the ship.

The flange takes pipes up to a maximum internal diameter of 100 mm. It is of steel or equivalent material with a flat face, and with a suitable gasket it is designed for a service pressure of 600 kPa. Ships with a moulded depth of 5 meters or less may fit a 38 mm inner diameter connection. Regulation 10.2 allows ships in dedicated trades, such as passenger ferries, to use an alternative connection acceptable to the Administration, for example quick-connection couplings.

The sewage flange differs from the oil flange in Annex I Regulation 13 , so a ship needs the right adaptor for each. The dimensional table and the ferry alternative are covered in the article on the standard discharge connection .

Discharge of sewage under Regulation 11

Regulation 11 was replaced in full by MEPC.200(62) and now has three parts: Section A for all ships other than passenger ships in a special area, Section B for passenger ships in a special area, and a rule on mixed wastes.

Regulation 11.1 prohibits the discharge of sewage into the sea except in three cases:

• Comminuted and disinfected sewage at a distance of more than 3 nm from the nearest land, using a system approved by the Administration under Regulation 9.1.2.
• Sewage that is not comminuted or disinfected at a distance of more than 12 nm from the nearest land.
• Effluent from an approved sewage treatment plant certified by the Administration to meet the operational requirements of Regulation 9.1.1, provided the effluent produces no visible floating solids and does not cause discoloration of the surrounding water.

The first two cases carry a further condition that applies “in any case”: sewage that has been stored in holding tanks, or that originates from spaces containing living animals, is not discharged instantaneously but at a moderate rate, with the ship en route and proceeding at not less than 4 knots, at a rate approved by the Administration based on standards developed by IMO. The condition follows the storage, not the treatment, so comminuted and disinfected sewage held in the temporary storage a Regulation 9.1.2 system requires is caught by it as well as raw sewage. Effluent discharged from an approved plant as it is produced carries no speed condition in Regulation 11.

Regulation 11.4 applies when sewage is mixed with wastes or waste water covered by other MARPOL annexes: the requirements of those annexes apply as well as Annex IV. Sewage mixed with oily bilge water is subject to the Annex I discharge rules, and food waste ground into a sewage line remains subject to the Annex V conditions.

Rate of discharge: MEPC.157(55)

The IMO standard for the approved rate is MEPC.157(55), adopted 13 October 2006 as a recommendation, and made relevant to the Annex text by MEPC.164(56), adopted 13 July 2007 and in force 1 December 2008. Paragraph 3.1 sets the maximum permissible discharge rate at 1/200,000 of the swept volume, the product of the ship’s breadth, draught and distance travelled.

The constant comes from the conversion of one nautical mile to 1,852 m divided by 200,000. The rate is averaged over 24 hours, or over the discharge period if shorter, and may be exceeded by no more than 20% when measured hourly (paragraph 3.2). The Administration approves the rate at the maximum summer draught and maximum service speed, and may approve secondary rates for other draught and speed combinations (paragraph 4.1). For a ship of 25 m breadth on a 9 m draught at 12 knots, the formula gives 0.00926 x 12 x 9 x 25 = 25.0 m3/h; the same ship at 4 knots on a 5 m draught may discharge 4.63 m3/h. Where a fixed-rate pump is fitted, it is calibrated for 4 knots or a stated higher minimum speed (paragraph 5.2), and the crew member operating it confirms the ship is en route, more than 12 nm from nearest land and at a speed consistent with the approved rate (paragraph 6.1).

MEPC.157(55) gives no credit for dilution: mixing holding-tank contents with grey water or seawater does not raise the permitted rate (paragraph 1.3). The recommendation is covered in the article on the MEPC.157(55) discharge rate .

Reception facilities under Regulations 12 and 13

Regulation 12.1 obliges each Party that requires ships operating in its waters and visiting ships to comply with Regulation 11.1 to ensure the provision of reception facilities for sewage at ports and terminals, without causing delay to ships and adequate to meet the needs of the ships using them. Regulation 12.2 requires Parties to notify IMO, for transmission to the Contracting Governments concerned, of all cases where facilities are alleged to be inadequate. Masters report inadequacy through the IMO format circulated as MEPC.1/Circ.834/Rev.1, and the reports and port facility lists are held in the GISIS port reception facilities database . The general duty is covered in the article on Annex IV Regulation 12 reception facilities .

Regulation 12.1bis, added by MEPC.216(63) (adopted 2 March 2012, in force 1 August 2013), lets Small Island Developing States meet the Regulation 12.1 duty through regional arrangements, under a Regional Reception Facilities Plan developed in consultation with IMO. The same resolution made the parallel change to Annex I Regulation 38 , Annex II Regulation 18 and Annex V Regulation 8 .

Regulation 13 applies only to special areas. Parties whose coastline borders a special area ensure that facilities for the reception of sewage are provided in ports and terminals in the special area used by passenger ships, adequate to meet their needs and operated without undue delay. Regulation 13.2 makes the effective date of the Baltic passenger-ship discharge prohibition depend on those facilities: IMO sets the date once sufficient notifications of adequate facilities have been received, and notifies Parties at least 12 months in advance. That mechanism is what produced the 2016 dates in MEPC.275(69). It is covered in the article on reception facilities for passenger ships in special areas .

The Baltic Sea Special Area

The Baltic Sea is the only Annex IV special area, and the rule applies only to passenger ships. MEPC.200(62), adopted 15 July 2011 and in force 1 January 2013, created the special-area provisions, defined special area by reference to the Baltic Sea area in Annex I Regulation 1.11.2, and added Regulation 11.3 and Regulation 9.2. The Baltic coastal States also regulate ship sewage through HELCOM (see the regional overlays below). The Baltic outside Russian waters is also a Particularly Sensitive Sea Area and an emission control area under Annex VI, which are separate designations with separate legal bases.

Regulation 11.3 prohibits the discharge of sewage from a passenger ship within a special area, unless the ship has an approved sewage treatment plant certified by the Administration to meet Regulation 9.2.1 and the effluent produces no visible floating solids and causes no discoloration. The plant must meet the section 4.2 nutrient standard of MEPC.227(64) as well as section 4.1:

• Total nitrogen: 20 Qi/Qe mg/l, or at least 70% reduction. Total nitrogen is the sum of total Kjeldahl nitrogen (organic and ammoniacal), nitrate-nitrogen and nitrite-nitrogen.
• Total phosphorus: 1.0 Qi/Qe mg/l, or at least 80% reduction.

Percentage reductions are computed from daily flow-weighted geometric means. Without a section 4.2 plant, a passenger ship holds all sewage while within the special area and delivers it ashore, or discharges it under Regulation 11.1 once outside.

Effective dates. MEPC.200(62) originally set 1 January 2016 for new and 1 January 2018 for existing passenger ships, subject to the reception-facility condition in Regulation 13.2. MEPC.274(69), adopted 22 April 2016 and in force 1 September 2017, replaced Regulation 11.3 so that the prohibition takes effect on a date set by IMO, in no event before 1 June 2019 for new passenger ships and 1 June 2021 for existing ones. MEPC.275(69), adopted the same day, fixed the dates:

The 28°10’ E line places St. Petersburg in the 2023 category. MEPC.274(69) also amended the ISPP Certificate form so that item 1.1 states whether the plant was certified to MEPC.227(64) “including” or “excluding” section 4.2, which is the line a port State control officer reads in the Baltic. The ship categories, the plant certification and the reception arrangements in Baltic ports are covered in the article on the Baltic Special Area rules for passenger ships .

Port State control under Regulation 14

Regulation 14 lets a Party inspect a foreign ship in its ports or offshore terminals for operational requirements under Annex IV where there are clear grounds for believing that the master or crew are not familiar with essential shipboard procedures relating to the prevention of pollution by sewage. Where that is found, the Party takes steps to ensure the ship does not sail until the situation is brought to order (Regulation 14.2). The procedures of MARPOL Article 5 apply (Regulation 14.3). The regulation was added by MEPC.143(54), adopted 24 March 2006 and in force 1 August 2007, as Regulation 13, and is numbered 14 under the 27 June 2014 correction of MEPC.200(62), with effect from 1 January 2013.

Port State control of Annex IV runs on the IMO Procedures for Port State Control , whose current edition is A.1206(34). Appendix 2 of A.1206(34) lists four Annex IV deficiencies that may justify detention:

1. absence of a valid ISPP Certificate;
2. a sewage treatment plant not approved and certified by the Administration;
3. failure of the sewage treatment plant;
4. ship’s personnel not familiar with the disposal and discharge requirements for sewage.

In an inspection, the officer may check whether the plant, comminuter or holding tank has been used, whether the crew know how to operate it, and whether they know the Regulation 11 discharge conditions. The Paris MoU deficiency coding records the ISPP Certificate as code 01119 and the Annex IV equipment group under 144, with 14402 for the sewage treatment plant, 14403 for the comminuting and disinfecting system, 14404 for the sewage discharge connection and 14499 for other Annex IV items. The Tokyo MoU applies the same IMO procedures. The inspection practice, clear-grounds examples and detention record are covered in the article on port State control under Annex IV .

Verification of compliance under Regulations 15 and 16

MEPC.246(66), adopted 4 April 2014 and in force 1 January 2016, added Chapter 6 to Annex IV, as it did to the other annexes. Regulation 15 requires Parties to use the provisions of the III Code in performing their obligations under the Annex. Regulation 16 makes every Party subject to periodic audits by IMO under the IMO Member State Audit Scheme to verify compliance with and implementation of the Annex.

Polar waters: Chapter 7 and the Polar Code

MEPC.265(68), adopted 15 May 2015 and in force 1 January 2017, added Chapter 7 to Annex IV. Regulation 17 defines the Polar Code, the Antarctic area (south of latitude 60° S) and Arctic waters. Regulation 18 requires all ships certified under Annex IV and operating in polar waters to comply with the introduction and Part II-A chapter 4 of the Polar Code .

Polar Code paragraph 4.2.1 permits discharge only in accordance with Annex IV and the following requirements, so the ice-measured distances apply in addition to the Regulation 11 distances from the nearest land:

• comminuted and disinfected sewage more than 3 nm from any ice-shelf or fast ice, and as far as practicable from areas of ice concentration exceeding 1/10;
• untreated sewage more than 12 nm from any ice-shelf or fast ice;
• plant effluent under Regulation 11.1.2, as far as practicable from the nearest land, any ice-shelf, fast ice or areas of ice concentration exceeding 1/10.

Paragraph 4.2.2 prohibits any discharge except through an approved plant for category A and B ships constructed on or after 1 January 2017, and for all passenger ships constructed on or after that date. Paragraph 4.2.3 allows category A and B ships operating for extended periods in ice concentrations over 1/10 to discharge only through an approved plant, subject to the Administration’s approval. The Antarctic overlay is covered in the article on the Antarctic special area and the Polar Code .

Amendment history

Annex IV has been amended by seven resolutions since the revised text was adopted. The table lists every resolution that has changed the Annex text, in order, starting with the revision itself.

The guidelines sit outside that list because they are not part of the Annex: MEPC.157(55) on the discharge rate, MEPC.227(64) on plant standards, MEPC.275(69) setting the Baltic dates, and MEPC.284(70) amending MEPC.227(64).

The original Annex IV, adopted with the 1973 Convention, entered into force on 27 September 2003, 30 years later. MEPC.115(51) followed on 1 April 2004, was deemed accepted on 1 February 2005 under the tacit acceptance procedure, and entered into force on 1 August 2005.

Revision under way at PPR

The Marine Environment Protection Committee has a comprehensive revision of Annex IV and its guidelines on the agenda of the Sub-Committee on Pollution Prevention and Response , aimed at the lifetime performance of sewage treatment plants rather than their performance on the type-approval test. At PPR 13, held 9 to 13 February 2026, the working group agreed in principle a draft Regulation 11A introducing a Sewage Record Book as a new appendix III, with recording guidance, and a draft Regulation 11B on Sewage Management Plans, with guidance. Both are subject to further review once the other revised provisions are closer to completion, and the correspondence group was re-established. PPR 12 in 2025 asked MEPC to extend the target completion year of the output to 2027.

None of it is in force. A draft regulation agreed in principle at a sub-committee still has to be approved by MEPC, circulated, adopted and accepted under MARPOL Article 16 before it binds anyone, which puts any entry into force well beyond the 2027 completion target. The work programme is tracked in the article on the Annex IV revision . Until it concludes, Annex IV requires no sewage log, so the MARPOL provisions on electronic record books have no sewage record to apply to.

Grey water outside Annex IV

Grey water is not regulated by MARPOL unless it is mixed with sewage. No IMO instrument sets a discharge limit for shower, galley, laundry or dishwasher water on its own, which the Bahamas Maritime Authority’s Marine Notice 59 states directly: grey water “is not considered sewage unless it is mixed with” the Regulation 1.3 drainages. The gap matters most on cruise ships, which carry the most people. Passenger-ship designs that route grey water through the same advanced wastewater treatment plant as black water bring the combined discharge under Regulation 11 and the type-approval standard.

National rules fill the gap in some waters. In Alaska, 33 CFR 159 Subpart E regulates graywater from cruise vessels alongside sewage. Canada’s 2023 interim order covers grey water from cruise ships (see below). Food waste in grey water is a separate matter, governed by Annex V . The national approaches are compared in the article on grey water discharge regulation .

Regional and national overlays

Annex IV is the international baseline. Four overlays change what a ship does in practice in their waters.

HELCOM and the Helsinki Convention

The 1992 Helsinki Convention, administered by HELCOM, has its own Annex IV on prevention of pollution from ships. Regulation 4(3) of that Annex required the Contracting Parties to apply revised MARPOL Annex IV Regulation 11 paragraphs 1 and 3 and the Regulation 12(1) reception duty from 1 January 2004, ahead of MARPOL’s own entry into force for the revised text. Regulation 5 goes below the MARPOL thresholds: all other ships with toilets, pleasure craft included, that are not covered by MARPOL Annex IV Regulation 2 are fitted with toilet retention systems, with a waiver in a Party’s own waters for ships built before 1 January 2000 where installation is technically difficult or costly relative to the ship’s value. Regulation 6 requires ships to discharge all ship-generated wastes that may not be discharged into the sea to a port reception facility before leaving port.

European Union: Directive (EU) 2019/883

The EU Port Reception Facilities Directive , adopted 17 April 2019, covers waste falling within MARPOL Annexes I, II, IV, V and VI, so sewage is in scope. It entered into force on the twentieth day after publication in the Official Journal of 7 June 2019, the transposition deadline was 28 June 2021, and it repealed Directive 2000/59/EC. The provisions that bear on sewage:

• Article 6: advance waste notification at least 24 hours before arrival where the port of call is known, on the Annex 2 form, which has a line for MARPOL Annex IV sewage in cubic meters.
• Article 7(1): the master delivers all waste carried on board before leaving the port, in accordance with the MARPOL discharge norms, and receives a waste delivery receipt (Article 7(2)).
• Article 8(2)(a) and (b): every ship pays an indirect fee irrespective of whether it delivers waste, covering indirect administrative costs and at least 30% of the total direct costs of reception.
• Article 8(2)(c): the guarantee that no direct fee is charged applies to MARPOL Annex V waste other than cargo residues. Sewage is not covered by it, so a port may levy a direct fee for sewage delivery.
• Article 9: exemptions from Articles 6, 7(1) and 8 for ships in scheduled traffic with frequent and regular port calls, with a delivery and fee arrangement at a port on the route, which may be a Union port or another port.

Every Baltic port outside the Russian Federation is an EU port, Helsinki, Tallinn, Riga, Klaipeda and Gdansk among them, so there the EU Directive and the Annex IV special-area rule apply together. Russian Federation ports, St. Petersburg among them, are outside the Directive and covered only by Annex IV Regulation 13 and the Helsinki Convention.

United States

The United States is not a Party to Annex IV, and its MARPOL implementing statute, the Act to Prevent Pollution from Ships , does not enforce Annex IV. Vessel sewage in US waters is regulated under section 312 of the Clean Water Act through marine sanitation device rules in 33 CFR Part 159 . Under 33 CFR 159.53:

• a Type I device produces effluent with a fecal coliform count not greater than 1,000 per 100 ml and no visible floating solids;
• a Type II device produces effluent not greater than 200 fecal coliforms per 100 ml and suspended solids not greater than 150 mg/l;
• a Type III device is designed to prevent the overboard discharge of treated or untreated sewage.

Cruise ships in Alaskan waters face a tighter federal regime under 33 CFR 159 Subpart E, enacted through Public Law 106-554. No untreated sewage may be discharged into the applicable waters of Alaska (159.307). Treated sewage and graywater may be discharged only while underway at not less than 6 knots and not less than 1 nm from the nearest shore, unless the ship qualifies for continuous discharge by meeting secondary-treatment standards, a 30-day geometric mean not over 20 fecal coliforms per 100 ml with not more than 10% of samples over 40, and total residual chlorine not over 10 micrograms per liter (159.309). The Alaskan rules are covered in the article on Alaska cruise ship discharge rules .

The Vessel Incidental Discharge Act excludes sewage from its scope. VIDA covers discharges incidental to the normal operation of a vessel, except sewage. The EPA published its final Vessel Incidental Discharge National Standards of Performance in October 2024, and the US Coast Guard has two years from the EPA rule to finalize the corresponding implementing regulations.

Canada

Transport Canada announced on 23 June 2023 mandatory measures for cruise ships, implemented by an Interim Order with immediate effect. The 2023 order prohibited the discharge of grey water and treated sewage within 3 nm from shore where geographically possible, and required grey water to be treated together with sewage, using an approved treatment device, before discharge between 3 and 12 nm south of latitude 60° N. Arctic waters are governed separately under the Arctic Waters Pollution Prevention Act, covered in the article on Canadian Arctic shipping pollution prevention . Penalties under the Canada Shipping Act, 2001 reach CAD 250,000. The measures are covered in the article on the Canadian cruise ship grey water interim order .

Annex IV and the other MARPOL annexes

Annex IV shares architecture with the other annexes and differs from them on the points a ship’s staff most often confuse.

Annex III , on harmful substances in packaged form, and Annex VI , on air pollution, do not regulate sewage. The Ballast Water Management Convention is a separate treaty for a separate stream, but the two meet on board: a ballast tank used to hold sewage or treated grey water temporarily brings both the sewage rules and the ballast water rules into play, and flag States set separation conditions for it in their own guidance, as the Bahamas Maritime Authority does in section 15 of Marine Notice 59. A passenger ship carries the heaviest Annex IV load of any type, since its persons on board, not its tonnage, drive the volume, which is why cruise operations dominate the special-area and grey-water questions.

Common misstatements about Annex IV

These errors recur in manuals, training material and secondary sources, and each is corrected by the text cited:

• “Total nitrogen 10 mg/l.” MEPC.227(64) section 4.2 sets 20 Qi/Qe mg/l or a 70% reduction.
• “95% of samples must meet the limits” or “a 100-day test”. Compliance is on the geometric mean of at least 40 samples over a test of at least 10 days (sections 4.1, 5.3 and 5.5.1).
• “Annual ISPP endorsement.” Regulation 4.1 provides no annual or intermediate survey.
• “The standard discharge connection is Regulation 7” or “reception facilities are Regulation 10”. Those are not the current numbers: the connection is Regulation 10, the general reception duty Regulation 12, passenger ships in special areas Regulation 13, port State control Regulation 14.
• “The 4-knot rule applies to all discharges.” It applies to stored sewage, raw or comminuted and disinfected, and to sewage from spaces containing living animals; effluent discharged from an approved plant as produced is not subject to it (Regulation 11.1.1).
• “Grey water is regulated by Annex IV.” Only when mixed with sewage (Regulation 1.3.4).
• “Regulation 3 exempts domestic voyages.” Domestic voyages are outside Regulation 2.1; Regulation 3 has only the safety and damage exceptions.
• “A Sewage Record Book is required.” Not under Annex IV as of October 2026.

Limitations

This article reports the text of Annex IV as revised by MEPC.115(51) and amended by the seven resolutions in the amendment table, and the guidelines MEPC.157(55), MEPC.227(64) and MEPC.284(70). The PPR revision may change the equipment, record-keeping and test requirements, and the draft Regulations 11A and 11B described here are drafts. The Regulation 1 paragraph numbers given are those confirmed by amending resolutions (1.3, 1.4, 1.5, 1.10 and 12 to 15); a consolidated edition is the reference for the others.

Flag-State interpretation fills much of the Annex: holding tank capacity, comminuter performance, approved discharge rates, and what counts as practicable for older ships are Administration decisions, and class rules add equipment requirements the Annex does not contain. The national overlays summarized here are the federal US rules, the Canadian interim order as announced in 2023, the Helsinki Convention and the EU Directive; state law in Alaska and other US states, later Canadian orders and port by-laws can be stricter and are not covered. The number of Contracting States is taken from the IMO Status of Treaties dated 30 September 2026 and changes as instruments of accession are deposited.

Related Articles

• MARPOL Convention
• MARPOL Annex IV Regulation 9: sewage systems
• MARPOL Annex IV Regulation 10: standard discharge connection
• MARPOL Annex IV Regulation 11: sewage discharge
• MARPOL Annex IV Regulation 13: reception facilities for passenger ships
• MARPOL Annex IV Regulation 14: port State control
• MARPOL Annex IV surveys and the ISPP Certificate
• MARPOL Annex IV Baltic Special Area for passenger ships
• MEPC.227(64) sewage treatment plant standard
• Marine sewage and grey water treatment systems
• Sewage holding tank sizing
• MARPOL special areas
• Polar Code
• MARPOL Annex V: garbage from ships