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Prohibition of discharge of sewage to the Thames

Both the Marine Strategy Framework Directive and Water Framework Directive have targets to improve water quality, including factors and pathogens attributed with discharge of sewage; such as minimisation of human induced eutrophication and E.Coli. With actions in place by major projects like Tideway Tunnel which have been extensively studied and published, along with investment in water treatment plant improvements already being carried out along the river, the land source of sewage is being significantly reduced.

International calling vessels must comply with MARPOL and recreational users are being encouraged not to discharge by the Green Blue campaign love where you sail. The latter quantifies that one flush from a vessel is equivalent to 250,000 flushes through the sewage system. The Thames has been failing to meet Urban Waste Water Treatment Directive (UWWTD) standards and the government supports actions to improve the water quality, such as the Tideway Tunnel, however there are other smaller actions that river users can do to contribute to improvements.


PLA Byelaw 49 came into force on 1 January 2015. The Byelaw prevents the discharge of sewage into the Thames from specified vessels, consistent with the continuing improvement of the Thames environment, particularly with Thames Water's project to stop the discharge of untreated sewage into the river, and brings the Thames into line with a number of other UK harbours and inland waterways.

For the purposes of this byelaw, sewage refers to faeces and urine plus any water associated with them. In some circumstances, sewage from vessels is known as "black water".

The full text of the Port of London Authority Byelaw 49 is reproduced below:


49.1 The owner of:

  1. a vessel licensed under section 124 of the Act or
  2. a houseboat

must, from 1 January 2015, ensure that no sewage is discharged into the Thames.

49.2 In this byelaw “houseboat” means any vessel (other than a ship registered under the Merchant Shipping Act 1995 or any vessel usually used for navigation) which is used primarily as a place of habitation, or as a place for accommodating or receiving persons for the purposes of shelter, recreation, entertainment or refreshment, or as club premises or offices, while it is moored.

* under all byelaws emergency failure can be considered by the harbourmaster at the time.

In 2021, these regulations were extended to the General Directions to cover all commercial vessels in the Thames, as currently the passenger boat industry and commercial sailing yachts are not required to contain their Blackwater. These revised General Directions went through consultation in 2021. International Vessels calling into the port must comply with MARPOL standards and are regulated by the MCA.

The full text of the Port of London Authority General Direction 10 is reproduced below:


10.1       From 1 July 2024, all commercial Vessels must ensure that they discharge no sewage into the Thames.

10.2       Vessels certificated in accordance with the Merchant Shipping (Vessels in Commercial Use for Sport or Pleasure) Regulations 1998 which only Occasionally navigate within the Thames are exempt from General Direction 10.1.

Grey Water

Byelaw 49 and General Direction 10 applies only to Sewage (also known as black water), but the discharge from your sinks (also known as grey water) can also have a detrimental effect on the environment.

We recommend that only phosphate-free detergents are used and advise that you use environmentally sensitive washing products where possible.

If possible, re-plumb wastewater systems so that both grey and black water are diverted to the holding tank and then disposed of by one of the methods outline above.

Useful Links

The Green Blue:
List of pump out facilities on the Thames.

Port of London Authority:
Leisure Facilities Directory

Small sewage treatment plants:
British Water Guidance
PPG4 – Guidance for treatment and disposal of sewage where no foul sewer is available
Reform of the regulatory system to control small sewage discharges from septic tanks and small sewage treatment plants in England
Septic tanks and treatment plants

Sewerage Undertakers:
Contact details for all water companies can be found at the OFWAT website.

Environment Agency:
Non-tidal Thames User Guide

Canals and River Trust
Sewage disposal points
Boating facilities searchable as "boat services"

All information provided herein is current at the time of publication. Inclusion in this guidance does not imply endorsement by the PLA.

Page updated: January 2022.