Holding Tanks

Information about the legislation relating to the discharge of black water from holding tanks at sea.

There are three terms which are commonly used to distinguish the different types of waste water created on boats: black water, grey water and bilge water.

  • Black water is toilet waste i.e. waste which will often contain harmful bacteria and viruses
  • Grey water is waste water from sinks, showers and washing machines
  • Bilge water is self explanatory but is often contaminated with oil.


The focus of the following information is holding tanks for black water.

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 fit 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.

International Conventions are however not the only legislation that concern private pleasure craft, as once a vessel is cruising within the territorial waters of another country it is under the jurisdiction of the coastal state.

In the context of holding tanks, this means that the coastal state could require visiting vessels to fit holding tanks in line with their national legislation, but this is seldom enforced for visiting boats.

That said, although a visiting vessel may not have to fit a holding tank, it should respect the Coastal State’s Law and should not discharge black water directly into the sea, where a local boat would be prohibited from discharging its holding tank.

Inland Waters

Internal waters, the waters landward of the Base Line (see Law of the Sea and the Coastal State for clarification of these terms), are considered to be an integral part of the Coastal State, therefore a foreign vessel visiting the inland waters of another country should be prepared to comply with any legislation that country may have in place, including regulations relating to holding tanks.


The Baltic

As with international conventions such as MARPOL, the Helsinki Convention (HELCOM Convention on the protection of the marine environment of the Baltic Sea Area) must be implemented in each of the participating countries through their national legislation. Therefore although HELCOM extends regulations on the discharge of sewage to all ships including pleasure craft, this is not yet law in all the HELCOM contracting parties: Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden.

The latest information we have regarding national legislation is as follows:

  • Boats built before 1 January 1980 do not have to have a holding tank and can discharge sewage when 2 nautical miles from the shore.
  • Boats built before 1 January 2000 but after 1 January 1980 which are either less than 10.5m LOA or have a maximum beam of less than 2.8m do not have to have a holding tank and can discharge sewage when 2 nautical miles from the shore.
  • Boats outside of the above exemptions, including all boats built after 1 January 2000 must have a holding tank that can be emptied through a deck fitting.



The discharge of untreated sewage is prohibited at a distance of less than 12 nautical miles from the nearest land i.e. within their territorial waters.


Boats under the German flag or that of another HELCOM signatory nation which were built after January, 1st, 2003 with a toilet on board must have a toilet retentions system in line with HELCOM recommendation 22/1.

Pleasure boats under the above mentioned flags, built between the named dates and having a toilet on board must have a toilet retention system if they have a length of more than 11,50 metres (Lh) and a width of more than 3,80 metres. If they fall below either this length or this width they do not have to have a tank.

It is possible for pleasure boats which exceed both measures to get an individual exemption if they prove to the competent authority that the fitting of a holding tank is technical impossible or the costs are economically disproportional.

The rules of MARPOL Annex IV on discharging apply to all pleasure boats that are fitted with a holding tank.


From 1 April 2015 all pleasure boats, including foreign flagged boats, are prohibited from discharging sewage into the lakes, internal waters and territorial waters (12 nautical miles) of Sweden. Recreational craft listed for preservation are not subject to the ban.

Sewage is any discharge of waste water and other waste from any type of toilet, including portable toilets. Sewage contains phosphorus and nitrogen and the primary aim of the ban is to reduce their discharge into Swedish waters.

Although a bucket, pot or similar does not count as a type of toilet and therefore falls outside the scope of the discharge ban, Sweden does have regulations which mean that anyone who is spending time outdoors should take every possible precaution not to contaminate the environment.

Pleasure boats can fit a holding tank, stop using the toilet and go ashore, or use a portable toilet, earth closet, incineration toilet or similar. It is not prohibited for a pleasure boat to have a directly discharging toilet as long as nothing is being discharged. If a boat does not have a toilet, sewage should not be discharged into the water but dealt with on land.

Marinas are responsible for ensuring that there are adequate facilities for boat owners to dispose of this waste on land.

A map showing the location of pump out stations can be found on the Swedish Transport Agency website.

Anyone caught not complying with the ban may face an on the spot fine.

The Mediterranean


Spain has holding tank requirements which together with their pollution legislation, essentially mean that vessels cannot discharge untreated sewage within Spanish territorial waters (12 nautical miles). The Spanish legislation is ORDEN FOM/1144/2003, 28 April which for anyone who speaks Spanish can be found at www.fomento.es and an unofficial translation of the legislation is also available.


In Greece the regulations relating to discharges and pollution make a holding tank a practical necessity although we are not aware of them being a legal requirement as yet. Caution should also be exerted with grey water in Greece.


Discharge of any kind may be considered illegal. A black water tank has therefore been a practical necessity in Turkey for many years. New rules have been coming into force in some areas of Turkey (such as the Mugla District) over the last few years which require vessels to carry a Blue Card. If the rules are enforced to the full all black and grey water will need to be collected and pumped out ashore; the Blue Card will be used to monitor the amount of waste water deposited ashore to ensure holding tanks are pumped out rather than emptied into the sea.



Discharge from toilets or holding tanks closer than 300 metres from shore is strictly prohibited.


Since January 2009 it has been prohibited to discharge black water (toilet waste) from all pleasure boats on all inland waterways, lakes, the Waddensea and territorial waters. Pleasure boats can be installed with holding tanks, dry or chemical toilets or boaters could choose simply not to use their toilets.


French law requires that as of 1 January 2008 new vessels, whether French or foreign flagged, are fitted with a treatment system or retention tank for black water if they wish to have access to French maritime or river ports, moorings and anchorages.

Users of older vessels which are not equipped with treatment systems or holding tanks for black water are, like all other pleasure yacht users, required to comply with the rules which prohibit discharge in ports and designated anchoring spots. They must therefore use shore toilets.

How these rules are to be applied or enforced is not very clear but it is anticipated that guidelines or a further law defining the extent and manner of application and any sanctions will be issued in the future.

In principle it is forbidden to flush toilets into canals and rivers, but as pump out facilities are few and far between until now discreet overboard discharging has been tolerated, this may of course change.


As yet Belgium has not, to our knowledge, introduced regulations which require private pleasure craft to have a holding tank. It is however prohibited to discharge or dump solid or liquid materials which may pollute the water both inland and at sea. See guide...on the water p.37.

Related pages

Advice on waste management


The Green Blue: https://thegreenblue.org.uk/