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Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.

Vessel Sewage PumpVessel Sewage Discharge

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The Clean Water Act sets out the principal framework for regulating sewage discharges from vessels in U.S. waters. The Act is implemented jointly by the U.S. Environmental Protection Agency and the U.S. Coast Guard.

Vessel sewage is generally controlled by regulating the equipment that treats or holds the sewage and through the establishment of areas in which the discharge of sewage from vessels is not allowed. Foreign vessels, operating in U.S. waters and beyond may also be covered by requirements developed though international treaties. Further, some regulations apply specifically to cruise ships, which present unique concerns with regard to water quality degradation.

Who is covered by the regulations?

Section 312 of the CWA requires the use of operable, U.S. Coast Guard-certified marine sanitation devices (MSDs) onboard vessels that are:

  • Equipped with installed toilets
  • Operating on U.S. navigable waters (which include the three mile territorial seas)

The requirements do not apply to vessels with "porta-potties" or similar self-contained units that do not discharge sewage into the water.

What is the purpose of the regulations?

Nutrients, metals, solids, toxics, and pathogens are among the types of pollutants present in sewage discharges, and, as such, these discharges have the potential to impair water quality, adversely affect aquatic environments, and increase risks to human health. While sewage discharges have potentially wide-ranging impacts on all aquatic environments, the impacts may be especially problematic in marinas, slow moving rivers, lakes, and other bodies of water with low flushing rates.


Under Chapter 33, section 1322 of the United States Code (33 CFR 1322), vessel sewage is controlled by regulating the equipment, termed marine sanitation devices (MSDs), that treats or holds the sewage. The Act also provides for the establishment of no discharge zones (NDZs), specific areas in which the discharge of sewage from vessels is not allowed. Within NDZ boundaries, vessel operators are required to retain their sewage discharges (treated and untreated) onboard for disposal at sea (beyond three miles from shore) or onshore at a pump-out facility. Under the CWA, the U.S. Coast Guard and the State in which the NDZ has been designated may enforce the NDZ requirements.

MSD Rules. The type of Marine Sanitation Device installed on vessels determines the specific rules that must be followed, as shown in the following table.

Type I

Flow-through treatment devices that commonly use maceration and disinfection for the treatment of sewage

May be installed only on vessels less than or equal to 65 feet in length

Must produce an effluent with:

  • No visible floating solids

  • A fecal coliform bacterial count not greater than 1000 per 100 milliliters

Type II

Flow-through treatment devices that may employ biological treatment and disinfection (some Type II MSDs may use maceration and disinfection)

May be installed on vessels of any length

Must produce an effluent with:

  • A fecal coliform bacterial count not greater than 200 per 100 milliliters

  • No more than 150 milligrams of total suspended solids per liter

Type III

Typically a holding tank where sewage is stored until it can be disposed of shore-side or at sea (beyond three miles from shore)

May be installed on vessels of any length

No performance standard, but pursuant to Coast Guard regulations, a Type III MSD must "be designed to prevent the overboard discharge of treated or untreated sewage or any waste derived from sewage."

NDZ Rules. Areas are designated as a No Discharge Zone by EPA and via state petitions through a process that may be initiated in one of three ways:

  • The State determines that the water body requires greater environmental protection and EPA determines that adequate facilities for the safe and sanitary removal and treatment of sewage from vessels are reasonably available (Commonly known as a 312(f)(3) NDZ). EPA does not evaluate the need for water body protection.

  • EPA, upon application by the State, determines that the protection and enhancement of the water body requires establishment of an NDZ (Commonly known as a 312(f)(4)(A) NDZ). Unlike NDZs established pursuant to CWA section 312(f)(3) (described above), the State does not have to show that adequate pump-out facilities are reasonably available to request that this type of NDZ be established.

  • Drinking Water Intake Zones. EPA, upon application by a State prohibits the discharge of sewage from vessels within a drinking water intake zone (Commonly known as a 312(f)(4)(B) NDZ). The State does not need to show that adequate pump-out facilities are reasonably available to establish this type of NDZ.

Under section 312 of the CWA, the U.S. Coast Guard and the State in which the NDZ has been designated may enforce the NDZ requirements.

Freshwater Discharge Prohibition. Vessels with installed toilets are also prohibited from discharging sewage into freshwater lakes, freshwater reservoirs, or other freshwater impoundments whose entrance point(s) and exit point(s) are too shallow to allow these vessels to enter and leave, and into rivers that do not support interstate traffic by vessels subject to section 312.

Foreign Vessels. Sewage discharges from foreign vessels may also be subject to additional rules established under the "International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 ("MARPOL Annex IV"). Although, the United States is not a party to MARPOL Annex IV, and thus, is not bound by the Annex's provisions, the majority (>80% by tonnage) of ocean-going vessels operating in U.S. navigable waters are registered in foreign countries that are subject to these requirements. Note that in 2009 the U.S. Coast Guard issued for U.S. flagged vessels voluntary MARPOL Annex IV compliance information. MARPOL Annex IV rules contain specific requirements for sewage treatment and discharges (e.g., comminuted and disinfected sewage using an approved system must be discharged at a distance of more than 4 nautical miles from the nearest land, or sewage which is not comminuted or disinfected at a distance of more than 12 nautical miles from the nearest land).

Cruise Ships. Cruise ships, which can carry 3,000 passengers or more and crew members, and often operate in pristine coastal waters present a special regulatory challenge. Some additional rules for cruise ships operating in Alaska are already in place. EPA is continuing to assess wastewater discharges from cruise ships and reviewing regulatory options for additional control.

Graywater. Under current federal law, graywater (wastewater generated from domestic activities such as laundry, dishwashing, and bathing) is not defined as a pollutant, nor is it generally considered to be sewage. There are no separate federal effluent standards for graywater discharges. The Clean Water Act only includes graywater in its definition of sewage for the express purpose of regulating commercial vessels in the Great Lakes, under the Section 312 MSD requirements. Thus, currently graywater can be discharged by vessels anywhere — except in the Great Lakes, where the Section 312 MSD rules apply.

NPDES General Permit. TERC users may question why EPA's NPDES Vessel General Permit (VGP) for vessel discharges has not been discussed in this section. Certain vessels are required to obtain coverage under EPA's NPDES Vessel General Permit (VGP) for discharges incidental to the normal operation of those vessels. However, vessel sewage discharges are excluded from coverage under the VGP. While sewage is defined as a "pollutant" under the CWA, sewage from vessels, which includes graywater in the case of commercial vessels operating on the Great Lakes, is exempt from the CWA Section 312 statutory definition. Therefore, vessel owners/operators are not required to obtain NPDES permits before discharging sewage. However, vessels that discharge graywater and sewage in one effluent stream, and are not otherwise "commercial vessels" for purposes of regulation under CWA section 312, are required to follow the requirements outlined in CWA section 312 and the under EPA's NPDES Vessel General Permit (VGP).

Best Practices

The Annex IV of MARPOL 73/78 Regulations for the Prevention of Pollution by Sewage from Ships is widely accepted as best management practices for vessel sewage disposal.

More Resources

No Discharge Zones by State. Tables list States where the current no discharge zones (NDZs) for vessel sewage are located. The tables also include the names of the waterbodies, the type of designation and a link to the Federal Register Notice describing the action.

Vessel Sewage Discharges: Statutes, Regulations, and Related Laws and Treaties.

Vessel Sewage Discharges Information. Related publications and links identified by EPA.