International requirements for the prevention of pollution from sewage are contained in the Vessel Pollution and Dangerous Chemicals Regulations in Annex IV of the International Convention for the Prevention of Pollution from Ships (MARPOL). Annex IV of MARPOL contains requirements for surveys, International Sewage Pollution Prevention Certificates, sewage treatment plants, discharging sewage, reception facilities and standard discharge connections and came into force on September 27, 2003.

Canada has acceded to Annex IV and adopted regulations concerning sewage pollution prevention in Division 4 – Sewage – of the Vessel Pollution and Dangerous Chemicals Regulations. These provisions replace the previous Great Lakes Sewage Pollution Prevention Regulations, Pleasure Craft Sewage Pollution Prevention Regulations and Non-Pleasure Craft Sewage Pollution Prevention Regulations. The regulations are a consolidation of the former regulatory requirements, the recommendations of a stakeholder working group established by Transport Canada Marine Safety, and the requirements of Annex IV of MARPOL.

Annex IV of MARPOL applies only to ships of 400 tons gross tonnage or more or certified to carry over 15 persons. The application has been expanded in the regulations to include all vessels in all Canadian waters and to all Canadian vessels everywhere. Previous regulations concerning sewage applied to ships, other than pleasure craft, only on the Great Lakes and to all vessels in a few areas designated for zero discharge. In Ontario, application includes pleasure craft under provincial legislation.

Section 86 of the regulations requires that a vessel has a toilet on board to have a holding tank or an approved marine sanitation device. With some exceptions, the discharge of untreated sewage into all Canadian inland waters and Canadian coastal waters within 3 nautical miles of land (ships less than 400 tons) and 12 miles of land (ships larger than 400 tons) is now banned. Treated sewage will only be allowed to be discharged into Canadian waters subject to specified limits of faecal coliforms per 100 ml of water. Adoption of these requirements permitted Canada to accede to Annex IV of MARPOL.