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Clubs, training centres, marinas and harbours play an important role in facilitating and educating boat users on the issues of black water and in promoting boat user best practice to help keep our waters clean, healthy and safe for other water uses.

What are the impacts of black water discharge?

  • Black water is a pollutant containing nutrients, metals, toxins and pathogens that can have a detrimental effect on natural ecosystems and wildlife, as well as risks to human health.
  • One flush on a boat contains the same amount of bacteria as 250,000 flushes through the sewage treatment process.
  • Can spread gastroenteritis when ingested by other water users e.g. swimmers, dinghy sailors.
  • Contains phosphorous and nitrogen which increase levels of algae growth. This algae covers the surface of the water blocking out sunlight and when it finally decomposes it depletes oxygen levels in the water which impacts on the survival of other aquatic species.
  • Chemicals such as chlorine, formaldehyde, ammonium and zinc compounds, used to disinfect breakdown and deodorise waste, are toxic to marine life.
  • It is unsightly and smells leading to an unpleasant experience by those recreating and working along our coastlines.

To prevent black water entering and polluting our waters boat users are encouraged to purchase a vessel with a holding tank or install one to enable them to dispose of this waste at onshore pump out facilities. Currently the number of pump out facilities around the UK coastline is not proportionate to the number of recreational boats with sea toilets and this needs to improve to facilitate boat users in adopting good practice and dispose of their waste responsibly.


To better inform boat users and to promote those who are providing pump out facilities, The Green Blue has a UK Pump Out Location Directory. We are currently updating this directory along with mapping other environmental facilities that marine operators may have, such as recycling and filtered/bunded wash down systems.  If your premises has one or more of these facilities available, then we encourage you to complete the 8 questions in our online UK Environmental Marine Facilities Survey.


However despite some areas having limited pump out facilities there is still boat user best practice that your club, centre or marine business can promote to staff, members and customers.




In the UK, The Environment Agency (EA) in England and Wales, the Scottish Environmental Protection Agency (SEPA) and the Northern Ireland Environmental Agency (NIEA) have overarching powers of regulation with regards to water pollution.

Inland Waters

Sewage discharge is prohibited by law on inland waterways in the UK. The Canal & River Trust provides an inland waterways interactive pump out facility map.


Coastal Waters

Regulations regarding the discharge of sewage are gradually increasing, however as yet there is no international convention which requires private pleasure craft to retrofit a holding tank, with the application for the latest wording for MARPOL (Marine pollution) chapter IV, only applying to vessels which exceed 400GT or carry more than 15 passengers. However sewage discharge can be prohibited as part of coastal and estuarine bylaws or marine operator policies for all recreational boaters.


Some European countries require that a holding tank is fitted by law and boat owners will also be required to install one if travelling through any of the UK’s inland canal routes e.g. Caledonian Canal in Scotland. You can find out more details on where these laws apply refer to the RYA’s Holding Tank advice.


Even if boating in an area that might have limited pump out facilities a holding tank will enable boaters to hold onto their black water until they are away from areas close to the shore, used by other water users e.g. swimmers and dinghy sailors, as well as away from enclosed areas such as marinas, harbours, sheltered waters  and other poorly flushed areas before discharging.


Although no specific provisions are made for smaller pleasure vessels, under 24m, in UK coastal waters, it is important for the boating community to consider the impact of discharging raw sewage into our waters and adopt boat user best practice to minimise water pollution.


As a club, training centre, or marine business you can help by:

  • Providing your own facilities such as a pump-out station and/or accessible on-shore toilets.
  • Promote your pump out facility or those nearby:
    • Add your pump out facility to, use and promote The Green Blue’s Coastal Pump Out Directory.
    • Encourage your local marina or harbour to install a pump out facility, especially if your members and training boats have holding tanks installed or are looking to install them.
  • Charter and Training Boats:
    • Install holding tanks on your charter or training boats. If you are purchasing new vessels, then you can request holding tanks to be fitted as new boats being built since 2017 must either have a space for one or a holding tank installed.
    • Visit our Product Directory to identify environmentally friendly cleaning products that can be in the heads and elsewhere onboard.
    • Provide recycled toilet paper which breaks down more easily than standard toilet paper and is more sustainably sourced.
    • Use signage to remind members, customers and staff to avoid flushing any items except toilet paper. Not only will these pollute our waters, it will block the heads and block and damage pump out facilities.
  • Raise awareness of the issues relating to black water and promote good practice by using The Green Blue’s Awareness Raising Toolkit, our  ‘What Can You Do?’ black water advise page for boat users.

Related Resources

Love Where You Sail
Water Pollution Campaign

Club, Centre & Marine Business

 Pump Out Locations

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Facilities and Operations

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