Guidance

General binding rules: small sewage discharge to a surface water

How to meet the general binding rules if your septic tank or small sewage discharge treatment plant releases (discharges) waste water to a surface water.

• From: Environment Agency
• Published: 16 June 2015
• Last updated: 2 October 2023 — See all updates

Applies to England

• Guidance for Northern Ireland
• Guidance for Scotland
• Guidance for Wales

Overview

If you’re the operator of a septic tank or small sewage treatment plant, you will not need a permit if you meet all of the general binding rules that apply to you.

The full set of rules is given in the publication Small sewage discharges in England: the general binding rules.

This guide explains which of the general binding rules you must meet if you discharge waste water to a surface water, such as a:

• river
• stream
• estuary
• lake
• canal
• coastal water

You must also have the other permissions that you need to discharge to the environment legally, including:

• appropriate building regulations approval
• planning permission, where necessary

There’s separate guidance on how to meet the general binding rules if your septic tank or small sewage treatment plant discharges to the ground.

Work out which rules apply to you

The general binding rules you must meet depend on when your discharge to a surface water started.

Existing discharges that started before 1 January 2015

You’re in this category if all these points apply:

• the discharge was already happening before 1 January 2015
• you have not changed the discharge from ground or a different surface water
• you have not moved the location of the discharge or, if you have, it’s still within 10 metres of the previous location
• you have not changed the volume or, if you have, it’s not greater than 5 cubic metres (5,000 litres) a day to surface water

If you have replaced your treatment system but all these points apply, you’re still in this category.

If so, you must meet the ’rules that apply to all discharges’. (Not the additional rules.)

Existing discharges that started on or after 1 January 2015 but before 2 October 2023

You’re in this category if, on or after 1 January 2015 but before 2 October 2023, you:

• started a discharge from small sewage treatment plant
• changed your discharge from ground to surface water
• moved the location of the discharge to more than 10 metres away from the previous location
• changed the volume of the discharge to more than 5 cubic metres (5,000 litres) a day to surface water

If so, you must meet the:

• rules that apply to all discharges
• additional rules for discharges started on or after 1 January 2015

New discharges that started on or after 2 October 2023

You’re in this category if, on or after the 2 October 2023, you:

• started a discharge from a small sewage treatment plant
• changed a discharge from surface water to ground
• moved the location of the discharge to more than 10 metres away from the previous location
• increased a discharge to ground to more than 5 cubic metres (5,000 litres) a day to surface water

If so, you must meet the:

• rules that apply to all discharges
• additional rules for discharges started on or after 1 January 2015
• additional rules for new discharges started on or after 2 October 2023

Rules that apply to all discharges

Rule 2: only discharge 5 cubic metres or less a day in volume

For sewage from a residential property, use the daily discharge calculator to work out how much you discharge a day.

For commercial properties (such as a hotel, restaurant or office) or holiday accommodation (such as a cottage or chalet), use British Water’s Flows and Loads guidance. You will need to add all sources of flow together.

If you discharge more than 5 cubic metres (5,000 litres) a day to surface water, you must connect to the public foul sewer when it’s reasonable to do so. You must apply for a permit if it’s not.

Rule 3: only discharge domestic sewage

The sewage must be domestic in nature. For example, from a toilet, bathroom, shower or kitchen of a house, flat or business (such as a pub, hotel or office).

Find out more about what the definition of domestic sewage includes.

Rule 4: do not cause pollution of surface water or groundwater

The sewage must not cause pollution – find out how to check for pollution.

Rule 6: 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.

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

• connect to a public foul sewer
• replace your septic tank with a small sewage treatment plant
• install a drainage field (also known as an infiltration system) – a series of pipes with holes placed in trenches and arranged so that the waste water can trickle through the ground for further treatment – and check if you meet the general binding rules for discharges to ground

You must have plans in place to do this work within a reasonable timescale, usually 12 months.

If you buy or sell a property with a septic tank that discharges directly into a watercourse

You should agree with the buyer or seller who will be responsible for replacing or upgrading the 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 provide a sewer for you to connect to. This is known as first time sewerage.

Rule 8: in tidal areas, make sure you discharge below the mean low water spring mark

If you’re in 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. Check the low water mark where you live.

Rule 9: make sure your treatment system meets the right British Standard

Your system must meet the relevant British Standard that was in place at the time it was installed.

The current standards for new systems are:

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

How to check if your treatment system met the British Standard

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

• it has a CE mark
• the manual or other documentation that came with your tank or treatment plant has a certificate of compliance with a British Standard
• it’s on British Water’s list of approved equipment

You can also ask the company that installed your equipment to confirm that it met the British Standard in place at the time of installation.

If your treatment system was installed before 1983 you do not need to do anything to meet the British Standard. There was no British Standard in place before then. You must still meet the other general binding rules that apply to you.

Non-British Standard systems

Retrofit systems within an existing septic tank can only be used if they were installed before 2007. If you have a system like this that was installed after that date, or you’re planning on installing one of these systems, you must apply for a permit.

You can only use a reedbed or a secondary treatment unit, installed after a septic tank, to discharge to a watercourse if it meets the relevant British Standard. Otherwise you must either:

• upgrade to a sewage treatment plant
• apply for a permit so the Environment Agency can assess the risk of using this sort of system in your location

Rule 10: make sure your treatment system is installed and operated correctly, and has 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, or installed one after 1 February 2006, you must check with the installer that it meets the sizing requirements in British Water’s Flows and Loads guidance.

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

If the amount of sewage the system needs to treat increases

You must make sure the treatment system is still big enough. For example, this could be if you extend your property or connect another property. You must recalculate the maximum daily volume of your discharge.

If you discharge more than 5 cubic metres (5,000 litres) a day to surface water you must connect to the public foul sewer when it’s reasonable to do so. You must apply for a permit if it’s not.

Rule 11: get your treatment system regularly maintained

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’s not in good working order. For example, this could be if it has:

• leaks
• cracks in tank walls or pipes
• blocked pipes
• signs that the waste water is not draining properly, like 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.

If you change your treatment system, check if it’s now classed as a new discharge. To do this, see the section ‘Work out which rules apply to you’.

Rule 12: get your treatment system regularly emptied

You must get the sludge that builds up in your sewage treatment plant removed (desludged) before it goes beyond the maximum capacity. You should do this at least 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. You can find this out by either:

• asking the company to confirm this when you arrange to have your tank emptied
• asking the tanker driver for a copy of the company’s waste carrier’s certificate

Rule 13: if 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

Rule 14: if you stop using your treatment system, make sure it’s decommissioned properly

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 discharges started on or after 1 January 2015

Rule 15: check if you can connect to a nearby public foul sewer

If you connect to a public foul sewer:

• the general binding rules will not apply to you
• you will not need a permit

To find out if there is a public sewer near your property, contact your local water company. You can also ask owners of neighbouring properties if their property is connected to a public sewer.

For a single domestic property

You cannot meet the general binding rules if there’s a public foul sewer within 30 metres of any boundary of the premises that your system serves.

If you’re building a development of more than one property

Multiply the number of houses by 30 metres.

Example If there are 3 properties then this will give you a distance of 90 metres (3 × 30 metres).

You cannot meet the general binding rules if any boundary of the premises that your system serves is within that distance of a public foul sewer.

If some or all of your discharge is from non-domestic properties

Divide the maximum volume in cubic metres that you want to discharge from those other premises by 0.75 (1 cubic metre is 1,000 litres). Multiply the result by 30. This will give you a result in metres.

Example A discharge of 1.2 cubic metres divided by 0.75 gives 1.6, which multiplied by 30 gives a result of 48 metres.

You cannot meet the general binding rules if any boundary of the premises that your system serves is within that distance of a public foul sewer.

If your discharge is in a sewered area

Check what you need to do if your discharge is in a sewered area.

If there’s no public foul sewer and a discharge can negatively affect the property or environment, check if your sewerage undertaker has a duty to to build and pay for a new sewer for you to connect to. This is known as first time sewerage.

Rule 17: make sure the discharge point is not in or near protected sites

You cannot meet the general binding rules if the discharge will be in or within 500 metres of any:

• biological sites of special scientific interest (SSSI)
• special protection areas
• special areas of conservation
• Ramsar wetland sites
• designated bathing water
• protected shellfish water
• freshwater pearl mussel population

You also cannot meet the rules if the 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

If you have or are planning to start a discharge to surface water in or near a protected site, you must connect to the public foul sewer when it’s reasonable to do so. You must apply for a permit if it’s not.

How to check the locations of protected sites

You can use Magic map to identify the locations of most of these sites.

1. Search for the discharge site location.

2. In the table of contents, open ‘Designations’, then ‘Land-Based Designations’, then ‘Statutory’. Select ‘Sites of Special Scientific Interest (England)’, ‘Special Protection Areas (England)’, ‘Special Areas of Conservation (England)’, ‘Ramsar Sites (England)’ and ‘Local Nature Reserves (England)’.

3. If the discharge will be to an estuary or the sea you should also open ‘Marine Designations’, then ‘Statutory’. Select ‘Special Protection Area (Marine) (GB)’, ‘Special Area of Conservation (Inshore) (GB)’, ‘Special Area of Conservation (Offshore) (GB)’ and ‘Bathing Waters 2016 (England)’. Also open ‘Marine’ in the table of contents, then ‘Fisheries and Fishing Activity’. Select ‘Shellfish Waters 2014 (England)’.

4. To measure the distance from the discharge site to any protected sites, select the ‘Measure’ tool from the menu then use the ‘Distance’ option.

5. To find out if a site is a biological SSSI or if a local nature reserve is aquatic, select the ‘Identify’ tool from the menu, then select the protected site on the map. Open the site detail link to read the description.

Magic map does not indicate the locations of freshwater pearl mussel populations, chalk rivers or aquatic local wildlife sites.

If you do not know whether the discharge will be in or near a protected site, or if you cannot use Magic, contact the Environment Agency to request a nature and heritage conservation screening.

Rule 19: make sure the surface water has flow

You cannot meet the general binding rules if you have a discharge to:

• a ditch or a surface water that does not contain flowing water throughout the year, unless there is a drought or an unusually long period of dry weather
• watercourses that seasonally dry up

Rule 20: Make sure any partial drainage field is close enough to the watercourse

A partial drainage field is a length of perforated pipe that is installed between the sewage treatment plant and the outfall. It’s installed instead of a solid pipe. This allows some of the waste water to soak into the ground when the ground is dry and flows in the watercourse are likely to be lower.

If you’re using a partial drainage field for a new discharge, the perforated section of the pipe must not extend more than 10 metres from the edge of the watercourse. You must only use it with a small sewage treatment plant, not a septic tank.

Rule 21: do not discharge to an enclosed lake or pond

You cannot meet the general binding rules if you have a discharge to an enclosed lake or pond. This means a lake or pond in which all of the following apply:

• it contains water throughout the year, other than in extreme weather conditions
• it does not have an outfall that connects it to a watercourse, or has an outfall that only discharges in extreme weather conditions
• it is sealed or lined to prevent water draining into the ground or soaking into the surrounding soil

You do not need a permit to discharge to an enclosed lake or pond. But you must use appropriate pollution prevention measures to make sure your discharge does not cause pollution.

Additional rules for new discharges started on or after 2 October 2023

Rule 22: make sure your new discharge does not use the same discharge point as any other discharge if the combined volume would exceed the general binding rule limit

A new discharge must not use the same outlet as any other discharge if the combined volume is greater than 5 cubic metres (5,000 litres) a day to surface water. You must have a permit for the new discharge if the combined volume of the new and existing discharges is above this limit.

Rule 23: make sure your new discharge is not within 50 metres of any other exempt small sewage discharge

Ask your neighbours if their foul drainage solution discharges under the general binding rules. If so, ask how far their discharge is from your discharge location.

You must have a permit for the new discharge if it’s within 50 metres of any other system that discharges under the general binding rules.

Get help following the rules

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

• what treatment system you have
• where your treatment system discharges
• what you must do to meet the general binding rules

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

If you cannot meet all of the rules that apply to you

You must either:

• connect to a public foul sewer – contact your sewerage undertaker for advice
• change your treatment system so that it can meet the general binding rules

Otherwise, you must apply for a permit.

In your permit application you must justify why it’s not reasonable to connect to a public foul sewer. The Environment Agency will then assess the risk of using your system at your location.

Enforcement

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.

Published 16 June 2015
Last updated 2 October 2023 + show all updates

1. 2 October 2023

   Added the new general binding rules that apply to discharges to surface water that started on or after 2 October 2023. Updated the guide's structure to clarify how to work out which rules apply to you.

2. 25 August 2021

   Updated definition of 'new discharges' so it also covers increases in volume of more than 5 cubic metres (5,000 litres) a day. Clarified definition of what we mean by 'enclosed lake or pond' (for rule 21).

3. 19 April 2021

   Updated guide structure. Explained how to identify if you have a 'new' and 'existing' discharge in more detail. Explained how to identify whether you meet each of the general binding rules in more detail. Explained how to get advice on understanding what system you have and what you are required to do. Explained what to do if you cannot meet all of the general binding rules that apply to you.

4. 7 January 2020

   Clarified that you can only use a septic tank conversion unit or a reedbed for discharging effluent to a water course under the general binding rules if it meets the relevant British Standard requirements.

5. 22 November 2019

   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.

6. 25 October 2019

   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.

7. 31 July 2019

   This guide only applies to England. We added links to guides for Northern Ireland, Scotland and Wales.

8. 4 July 2019

   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.

9. 25 June 2019

   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.

10. 5 July 2018

    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.

11. 16 June 2015

    First published.