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.

This guide explains which of the rules you must meet if you discharge waste water to the ground.

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 a surface water.

Work out which rules apply to you

The general binding rules you must meet depend on when your discharge to ground 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 surface water to ground
• you have not moved the location of the discharge or, if you have, it is still within 10 metres of the previous location
• you have not changed the volume of the discharge or, if you have, it’s not more than 2 cubic metres (2,000 litres) to ground

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 a septic tank or small sewage treatment plant
• changed your discharge from surface water to ground
• 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 2 cubic metres (2,000 litres) a day to ground

If so, you must meet the:

• rules that apply to all discharges
• additional rules for discharges that 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 septic tank or 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 2 cubic metres (2,000 litres) a day to ground

If so, you must meet the:

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

Rules that apply to all discharges

RuleOnly 1: only discharge 2 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 2 cubic metres (2,000 litres) a day to ground 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.

RuleOnly 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.

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

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

RuleUse 5: use the correct treatment system

You must use a septic tank or a small sewage treatment plant to treat the sewage and then discharge the waste water to ground through a drainage field. You must not discharge effluent from a septic tank to a watercourse.

A septic tank is an underground tank where the solids sink to the bottom, forming a sludge, and the waste water flows out to a drainage field.

A small sewage treatment plant, also known as a package treatment plant, works in a similar way to a septic tank. But it uses mechanical parts to treat the waste water to a higher standard before it goes to a drainage field.

A drainage field, also known as an infiltration system, is a series of pipes with holes placed in trenches. These are arranged so that the waste water can trickle through the ground for further treatment.

The system you use must meet the relevant British Standard (see– rulesee 9).the section ‘Make sure your treatment system meets the relevant British Standard’.

Discharges through drainage mounds can meet the general binding rules if:

• they are not in floodplains
• they are located, designed and constructed in line with the recommendations in British Standard BS 6297:2007

Discharges to ground which has been engineered to reduce the percolation rate can meet the general binding rules if:

• they are not in floodplains
• the engineered ground has a minimum percolation value (Vp) of 15
• they are located, designed and constructed in line with all other recommendations in British Standard BS 6297:2007

If you use a non-standard system (such as a well, borehole and soakaway)

You cannot meet the general binding rules if you’re using:

• a well or borehole to discharge waste water to ground
• a soakaway (designed for draining rainwater) installed after December 2007

Instead you must either:

• upgrade to a drainage field that meets British Standards (see rule 9) and check whether you meet the other general binding rules that apply to you
• connect to the public foul sewer when it’s reasonable to do so – you must apply for a permit if it’s not

You should avoid using non-standard systems such as boreholes, shafts, concrete rings or similar structures for new discharges to ground. These are not usually appropriate ways of disposing of sewage effluent because of their increased risk of pollution.

If your sewage effluent discharges directly to groundwater (at any time of year) through any of these non-standard systems:

• the Environment Agency will not grant you a permit
• you must replace this with a correct treatment system

This is explained in section G of the Environment Agency’s approach to groundwater protection.

RuleMake 7: make sure the discharge is not in a groundwater source protection zone 1

To prevent groundwater pollution you must check if the discharge point is in a groundwater source protection zone 1 (SPZ1).

A groundwater SPZ1 can be the area around a commercial water supply used for drinking water or food production. To check if your discharge is in the inner zone (zone 1) you can either:

• use Magic map – search for the discharge location, then select ‘Source Protection Zones merged (England)’ from the non-statutory land-based designations in the table of contents
• contact the Environment Agency to request a nature and heritage conservation screening if you cannot use Magic map

A groundwater SPZ1 can also be any area within 50 metres of a private water supply for human consumption. Ask your neighbours if they have one and, if so, how far their spring, well or borehole is from your drainage field.

If an existing discharge or a new discharge to the ground is in a SPZ1

If the discharge point is in a SPZ1 (except SPZ1c) you must apply for a permit. A permit will include additional conditions to the general binding rules.

The Environment Agency will grant the permit if either:

• there’s no evidence of pollution
• the risk of pollution is acceptable

If there’s evidence of pollution or the risk of pollution is unacceptable, the Environment Agency will ask you to make changes to your system. They will either refuse to grant a permit or issue a permit with improvement conditions.

The Environment Agency regularly checks:

• surface and groundwater quality
• permit compliance

If the Environment Agency finds your system may be causing pollution to surface or groundwater they will contact you to discuss the issues. This may result in them reviewing or revoking your permit. Follow the guidance on how to comply with your permit.

RuleMake 9: make sure your treatment system meets the rightrelevant British Standard

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

If different parts of your treatment system were installed at different times, each part must meet the relevant British Standard in place at the time of installation.

The current standards for new systems are:

• BS EN 12566 for septic tanks and 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.

RuleMake 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 septic tank, small sewage treatment plant or drainage field (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 to an another property. You must recalculate the maximum daily volume of your discharge.

If you discharge more than 2 cubic metres (2,000 litres) a day to ground 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.

RuleGet 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 is 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’.

RuleGet 12: get your treatment system regularly emptied

You must get the sludge that builds up in your septic tank or 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.

If you do not desludge your tank often enough, solids from the tank are likely to be carried into the drainage field or soakaway. This can cause damage and pollution, leading to potentially expensive and disruptive repairs.

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
• tanker driver for a copy of the company’s waste carrier certificate

RuleIf 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 septic tank or small sewage treatment plant) in writing that a sewage discharge is in place.

Include:

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

RuleIf 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

RuleCheck 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 an environmental permit

To find out if there is a public foul sewer near your property, contact your local water company. Owners of neighbouring properties will also be able to tell you 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.

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.

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.

RuleGet 16: get building regulations and planning approval

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

RuleMake 18: 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 an ancient woodland or in or within 50 metres of any:

• special areas of conservation
• special protection areas
• Ramsar wetland sites
• biological sites of special scientific interest (SSSI)

If you have or are planning to start a discharge to ground 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 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)’ and ‘Ramsar Sites (England)’.

3. In the table of contents, open ‘Habitats and Species’, then ‘Habitats’, then ‘Woodland’ option. Select ‘Ancient Woodland (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, select the ‘Identify’ tool from the menu, then select the protected site on the map. Open the site detail link to read the description.

If you cannot use Magic map, contact the Environment Agency to request a nature and heritage conservation screening.

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

RuleMake 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 2 cubic metres (2,000 litres) a day to ground. You must have a permit for the new discharge if the combined volume of the new and existing discharges is above this limit.

RuleMake 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.