Guidance

General binding rules: small sewage discharge to a surface water

Rules you must follow if your septic tank or small sewage discharge treatment plant releases (discharges) liquid to a surface water.

You must read septic tanks and treatment plants: permits and general binding rules before you follow this guidance.

The requirements changed on 1 January 2015. If your system was installed and discharging before 31 December 2014 you have an ‘existing discharge’. If your system was installed and discharging on or after 1 January 2015 you have a ‘new discharge’.

If your discharge causes pollution you may be committing an offence. The Environment Agency will give you advice to help you fix the problem. If your discharge continues to cause pollution the Environment Agency may take enforcement action against you.

Rules for existing and new treatment systems

Use the correct treatment system

You must use a small sewage treatment plant to treat the sewage if you’re discharging to a watercourse such as a river or stream. A sewage treatment plant (also known as a package treatment plant) treats sewage to a higher standard than a septic tank.

Discharges from septic tanks directly to watercourses are not allowed under the general binding rules.

You should get advice from a competent service engineer if you need help understanding what:

  • treatment system you have
  • you are required to do under the general binding rules

British Water provides a list of accredited service engineers. There may be other competent service engineers.

If your septic tank discharges directly to a watercourse, you need to do one of the following as soon as possible:

  • connect to mains sewer
  • install a drainage field (also known as an infiltration system) so the septic tank can discharge to ground instead
  • replace your septic tank with a small sewage treatment plant

You must have plans in place to carry out this work within a reasonable timescale, typically 12 months.

You cannot use a septic tank conversion unit or a reedbed for discharging effluent to a watercourse under the general binding rules. Instead you must either upgrade to a package treatment plant or apply for a permit so that the Environment Agency can assess the risk of using this sort of system in your location. If you apply for a permit you will need to include supporting information to show that the treatment system will treat your sewage to an appropriate standard.

Buy or sell a property with a septic tank

If you are buying or selling a property with a septic tank that discharges directly to a watercourse, you should agree with the buyer or seller who will be responsible for the replacement or upgrade of the existing treatment system. You should agree this as a condition of sale.

New sewer: first time sewerage scheme

If more than one property needs to replace or upgrade their sewerage system, your sewerage undertaker may have a legal duty to build and pay for a new sewer for you to connect to. This is known as a first time sewerage scheme. Contact your sewerage undertaker to find out how to apply. Contact the Environment Agency if you:

  • cannot identify how to make an application to your sewerage undertaker
  • want to appeal your sewerage undertaker’s decision

Your treatment system must meet the right British Standard

Your treatment system must meet the relevant British Standard that was in force at the time of installation. The standards currently in force for new systems are:

  • BS EN 12566 for small sewage treatment plants
  • BS 6297:2007 for drainage fields

Your treatment plant met the British Standard in place at the time of installation if:

You can also ask the company that installed your equipment to confirm that it complies with the British Standard that was in place at the time the equipment was installed.

If your treatment system was installed before 1983 there was no British Standard in place. You do not need to do anything to meet the British Standard requirement. You must still meet all the other general binding rules.

Your treatment system must be installed properly and have enough capacity

Your treatment system must be large enough to handle the maximum amount of sewage it will need to treat. If you install a new small sewage treatment plant you must check with the installer that it meets the sizing requirements in British Water’s Flows and Loads 4 guidance.

If the amount of sewage the system needs to treat increases (for example, because you’ve extended your property or connected an additional property) you must make sure the treatment system is still big enough. You must also recalculate the maximum daily volume of your discharge and apply for a permit if it is more than 5 cubic metres (5,000 litres) a day.

Your treatment system must be installed in line with the manufacturer’s specification (the instruction manual or technical set of requirements that comes with the equipment).

If you’re in a tidal area (an area where the water level changes according to tides), you must make sure the top end of the pipe that releases sewage is below the ‘mean low water spring mark’.

This is the average low water mark at the time of spring tides. Find out the low water mark where you live on the Admiralty tide tables.

Contact the Environment Agency if your exact location is not shown.

Have your treatment system regularly emptied and maintained

You must get the sludge which builds up in your sewage treatment plant removed (desludged) before it exceeds the maximum capacity. As a minimum, you should have your treatment system desludged once a year or in line with the manufacturer’s instructions.

The company you use to dispose of your waste sludge must be a registered waste carrier. Ask the company to confirm this when you arrange to have your tank emptied or ask the tanker driver for a copy of the company’s waste carrier’s certificate.

You should have your treatment system regularly maintained in line with the manufacturer’s instructions. If these are not available, ask your local maintenance company for advice.

You must have your treatment system repaired or replaced if it is not in good working order, for example if it has:

  • leaks
  • cracks in tank walls or pipes
  • blocked pipes
  • signs that the effluent is not draining properly (pools of water around the drainage point)
  • sewage smells
  • a failed motor
  • a failed pump
  • a failed electrical supply

Anyone who carries out maintenance on your system must be competent. Competent people include those on British Water’s list of Accredited Service Engineers.

You sell your property - tell the new owner about the sewage treatment system

If you sell your property, you must tell the new operator (the owner or person responsible for the sewage treatment plant) in writing that a sewage discharge is in place.

Include:

  • a description of the treatment plant and drainage system
  • the location of the main parts of the treatment plant, drainage system and discharge point
  • details of any changes made to the treatment plant and drainage system
  • details of how the treatment plant should be maintained, and the maintenance manual if you have one
  • maintenance records if you have them

You stop using your treatment system - make sure it’s properly decommissioned

You must remove anything that could cause pollution (for example, remaining sludge) when you stop using a septic tank or sewage treatment plant.

This does not apply if you only stop using the equipment temporarily, for example if your property is empty.

You can ask a maintenance company for advice on how to decommission your septic tank or treatment plant properly.

Additional rules for new treatment systems installed and in use on or after 1 January 2015

You must follow these additional rules if you:

  • started a new discharge from a small sewage treatment plant on or after 1 January 2015
  • had a discharge to ground before 1 January 2015 which you now want to change to discharge to a surface water (or the other way round)
  • had a discharge to a surface water before 1 January 2015 and you want to install a new drainage pipe which discharges more than 10 metres away from the existing one or which goes to a different surface water

Check if there’s a public sewer nearby

If any part of the building your treatment plant serves is within 30 metres of a public sewer, the Environment Agency will not allow you to start a new discharge from a sewage treatment plant under the general binding rules.

If you are building a development of more than one property, this distance must be multiplied by the number of properties. For example, if there are 3 properties then the distance will be 3 x 30 metres = 90 metres.

To find out if there is a public sewer near your property, contact your local water company.

If there is a good reason why you cannot connect to the sewer (for example, there is a river or a hill in the way) then you must apply for a permit so that the Environment Agency can decide whether to allow you to use a sewage treatment plant instead. Contact the Environment Agency to find out what information you will need to put in your application.

Building regulations and planning approval

You must have building regulations approval if you have or are planning to install a new sewage treatment plant. You may also need planning permission.

Check if the discharge point is in or near a designated sensitive area

If you have or are planning to start a new discharge to a surface water in or near to a designated sensitive area, you must apply for a permit.

You will need a permit if the new discharge will be in or within 500 metres of any:

You will also need a permit if the new discharge will be in or within:

  • 200 metres of an aquatic local nature reserve
  • 50 metres of a chalk river or aquatic local wildlife site

Contact the Environment Agency to check if you’re in or near a designated sensitive area and to find out if you need a permit.

Make sure the surface water has flow

New discharges are not allowed to a ditch or a surface water that does not contain flowing water throughout the whole year. That is unless there is a drought or an unusually long period of dry weather.

New discharges to watercourses that seasonally dry up are not allowed under the general binding rules, nor are discharges to enclosed lakes or ponds.

Contact the Environment Agency if you are unsure whether the surface water you want to discharge to is suitable.

Using a partial drainage field - check it meets the requirements

A partial drainage field (also known as a seasonal soakaway) is a system for discharging to water which allows effluent to drain into the ground when levels in the watercourse are low, and into the watercourse when groundwater levels are high.

If you’re using a partial drainage field for a new discharge, you must install it within 10 metres of the edge of the watercourse and you must only use it with a small sewage treatment plant, not a septic tank.

See the full list of general binding rules published by the government.

If there are any rules you cannot comply with contact the Environment Agency to discuss what you need to do.

Enforcement and sanctions

See the Environment Agency approach to enforcement, sanctions and offences.

Published 16 June 2015
Last updated 22 November 2019 + show all updates
  1. We have made 2 changes for clarity under the heading 'Use the correct treatment system'. 1) We have stated that there may be other competent service engineers in addition to those on the list provided by British Water. 2) We have added: You cannot use a septic tank conversion unit or a reedbed for discharging effluent to a watercourse under the general binding rules.
  2. We’ve updated this guide. Your discharge must not cause pollution. If you have a septic tank that discharges directly to a watercourse you need to take action as soon as possible to make sure you meet requirements.
  3. This guide only applies to England. We added links to guides for Northern Ireland, Scotland and Wales.
  4. Updated the section on ‘Building regulations and planning approval’. You must have building regulations approval if you have or are planning to install a new sewage treatment plant. You may also need planning permission.
  5. Updated the section on ‘Rules for existing and new treatment systems’ to make it clear that: You do not need to meet the British Standard requirement if your treatment system was installed before 1983. You must still meet all the other general binding rules.
  6. New sentence to clarify the rules for existing and new treatment systems: Where properties with septic tanks that discharge directly to surface water are sold before 1 January 2020, responsibility for the replacement or upgrade of the existing treatment system should be addressed between the buyer and seller as a condition of sale.
  7. First published.