Statutory guidance

SR2025 No 6: domestic sewage effluent with a maximum daily volume of 1.5 cubic metres per day to ground via an infiltration system that is not built to British Standard BS6297

Published 20 April 2026

Applies to England

The Environmental Permitting (England & Wales) Regulations 2016

Introductory note

This introductory note does not form a part of these standard rules.

When referred to in an environmental permit these rules will allow the operator to discharge domestic sewage effluent with a maximum daily volume of 1.5 cubic metres per day to ground via an infiltration system that is not built to British Standard BS6297, providing that no part of the infiltration system constructed is more than 1.4 metres below ground level and that it is replacing an existing discharge to surface water or to ground.

All works and equipment used for the treatment of sewage effluent (the treatment plant) must comply with the relevant design and manufacturing standards, meaning the British Standard that was in force at the time of the installation, and guidance issued by the appropriate authority on the capacity and installation of the equipment.

The discharge must not be made within a groundwater source protection zone 1 (SPZ1) or within 125 metres of any well, spring or borehole that is used to supply water for domestic drinking or food production purposes. The sewage must be secondary treated, and if the discharge takes place on a principal or secondary A aquifer, then any effluent discharged must not exceed a limit of 10 milligrams per litre (mg/l) of ammoniacal nitrogen (expressed as N).

The discharge must not be made in, or within, 50 metres of a European site, Ramsar site, biological Site of Special Scientific Interest (SSSI), Marine Conservation Zone, National Nature Reserve, Local Nature Reserve, Local Wildlife Site, water-based protected habitat or body of water known to contain protected species that the Environment Agency considers is at risk from this activity and must not be in an Ancient Woodland.

At the time the discharge is first made, it must not be made to a discharge point within 50 metres of any other exempt or permitted sewage effluent discharge to ground or surface water. 

All works on the equipment (for example, installation, servicing and testing) must be undertaken by a competent person and it is recommended that the person has a relevant accreditation, for example the British Water accreditation for treatment plant service technicians or manufacturer accreditation for installation.

End of introductory note.

Rules

1. Management

1.1 General management

1.1.1 The operator shall manage and operate the activity:

(a) in accordance with a written management system that identifies and minimises risks of pollution, so far as is reasonably practicable, including those risks arising from operations, maintenance, accidents, incidents, non-conformances, and those drawn to the attention of the operator as a result of complaints; and

(b) using sufficient competent persons and resources.

1.1.2 Records demonstrating compliance with rule 1.1.1 shall be maintained.

1.1.3 Any person having duties that are or may be affected by the matters set out in these standard rules or the permit shall have convenient access to a copy of the permit and the rules.

2. Operations

2.1 Permitted activities

2.1.1 The only activity authorised by the permit is the discharge into land of secondary treated domestic sewage effluent with a maximum daily volume of 1.5 cubic metres per day via an infiltration system that is not built to British Standard BS6297, providing that no part of the infiltration system constructed is more than 1.4 metres below ground level and that it is replacing an existing discharge to surface water or ground.

The activity is limited to:

(a) the maximum daily volume shall not be greater than 1.5 cubic metres per day as calculated by the method specified in the current edition of “Flows and Loads”. The sewage shall be solely domestic sewage and contain no trade effluent (as defined in Section 221 of the Water Resources Act 1991)

(b) the sewage effluent must be secondary treated

(c) all works and equipment used for the treatment of sewage effluent (the treatment plant) must comply with the relevant design and manufacturing standards, meaning the British Standard that was in force at the time of the installation, and guidance issued by the appropriate authority on the capacity and installation of the equipment

(d) the infiltration system shall be constructed to comply with the following:

(i) no part of the infiltration system constructed shall be more than 1.4 metres below ground level

(ii) no part of the infiltration system shall be less than 1.2 metres above the highest predicted annual groundwater level

(iii) the infiltration system shall not connect to any land drainage system

(iv) the infiltration system shall not be situated within 10 metres of any watercourse (including any ditch that runs dry for part of the year), or any other surface water

(v) the infiltration system shall not be situated within SPZ1, or 125 metres of a well, spring or borehole that is used to supply water for domestic or food production purposes

(e) the boundary of the premises that the sewage treatment system serves must not be within 30 metres of a public foul sewer. If the sewage treatment system serves more than one property, then it must not be within a distance that is less than 30 metres multiplied by the number of properties served

(f) if some or all of the discharge is from non-domestic properties, then the maximum volume in cubic metres that is being discharged from those other premises should be divided by 0.75 and the result multiplied by 30. The result is a distance in metres and no boundary of the premises that the sewage treatment system serves can be within that distance of a public foul sewer

(g) the ground beneath the drainage area into which the effluent is discharged must have a percolation rate (Vp) of between 15 and 100 seconds per millimetre. The Vp must be established in accordance with the methodology specified in BS6297. If the percolation rate is below 15 seconds per millimetre, then the ground must be engineered to achieve a minimum percolation rate of 15 seconds per millimetre (for example through the addition of a sand layer)

(h) the works and equipment shall be serviced a minimum of once every 12 months (or more if required by the manufacturer’s specifications) by a competent and suitably qualified person. Records demonstrating compliance with this rule shall be maintained by the operator

(i) no chemical dosing or electrocoagulation shall be used as part of the effluent treatment process

2.2 The site

2.2.1 The groundwater activity shall take place at the discharge point marked on the site plan attached to the permit.

2.2.2 The discharge shall not be made within a groundwater source protection zone 1.

2.2.3 The discharge shall not be made within 125 metres of any well, spring or borehole that is used to supply water for domestic drinking or food production purposes.

2.2.4 The discharge must not be made in, or within, 50 metres of a European site, Ramsar site, biological SSSI, Marine Conservation Zone, National Nature Reserve, Local Nature Reserve, Local Wildlife Site, water-based protected habitat or body of water known to contain protected species that the Environment Agency considers is at risk from this activity and must not be in an Ancient Woodland.

2.2.5 At the time the discharge is first made, it must not be made to a discharge point within 50 metres of any other exempt or permitted sewage effluent discharge to ground or surface water. 

3. Emissions and monitoring

3.1 Emissions to water or land

3.1.1 The limits given in Table 3.1 shall not be exceeded.

Table 3.1 Point source emissions to land – emission limits and monitoring requirements

Emission point and source	Parameter	Limit (including unit)	Monitoring frequency and standard or method
Discharge point for secondary treated domestic sewage effluent on a principal or secondary A aquifer	Maximum daily discharge volume	1.5 cubic metres per day	Not applicable
Discharge point for secondary treated domestic sewage effluent on a principal or secondary A aquifer	Ammoniacal nitrogen (expressed as N)	10 milligrams per litre	Not applicable
Discharge point for secondary treated domestic sewage effluent on a principal or secondary A aquifer	Visible oil or grease	No significant trace present so far as is reasonably practicable	Not applicable
Discharge point for secondary treated domestic sewage effluent on a secondary B aquifer, secondary Undifferentiated or unproductive strata	Maximum daily discharge volume	1.5 cubic metres per day	Not applicable
Discharge point for secondary treated domestic sewage effluent on a secondary B aquifer, secondary Undifferentiated or unproductive strata	Visible oil or grease	No significant trace present so far as is reasonably practicable	Not applicable

3.2 Emissions of substances not controlled by emission limits

3.2.1 For the activity referenced in condition 2.1.1, the operator shall take appropriate measures as far as is reasonably practicable:

(a) to prevent the input of hazardous substances to groundwater; and

(b) where a non-hazardous pollutant is not controlled by an emission limit, to limit the input of such non-hazardous pollutants to groundwater so as to ensure that inputs do not cause pollution of groundwater.

3.3 Monitoring

3.3.1 An accessible monitoring point shall be provided and maintained to enable monitoring to be carried out at the monitoring point marked on the site plan attached to the permit.

4. Information

4.1 Records

4.1.1 All records required to be made by conditions 2.1.1 and 4.3.2 shall:

(a) be legible;

(b) be made as soon as reasonably practicable;

(c) if amended, be amended in such a way that the original and any subsequent amendments remain legible, or are capable of retrieval; and

(d) be retained, unless otherwise agreed in writing by the Environment Agency, for at least 6 years from the date when the records were made.

4.1.2 The operator shall maintain convenient access, in either electronic or hard copy, to the records, plan and management system required to be maintained by these standard rules.

4.2 Reporting

4.2.1 The operator shall send all reports and notifications required by these standard rules to the Environment Agency using the contact details supplied in writing by the Environment Agency.

4.3 Notifications

4.3.1 The Environment Agency shall be notified as soon as reasonably practicable following detection, within the site of the regulated facility of:

(a) any malfunction, breakdown or failure of equipment or techniques, accident, or emission of a substance not controlled by an emission limit which has caused, is causing or may cause significant pollution; and

(b) any breach of a limit specified in these standard rules.

Any other significant adverse environmental effects, which may have been caused by the activity, shall also be notified to the Environment Agency as soon as reasonably practicable following detection.

4.3.2 Written confirmation of actual or potential pollution incidents and breaches of emissions shall be submitted within 24 hours.

4.3.3 The Environment Agency shall be notified within 14 days of the occurrence of the following matters except where such disclosure is prohibited by Stock Exchange rules:

(a) Where the operator is a registered company:

• any change in the operator’s trading name, registered name or registered office address; and
• any steps taken with a view to the operator going into administration, entering into a company voluntary arrangement or being wound up.

(b) Where the operator is a corporate body other than a registered company:

• any change in the operator’s name or address; and
• any steps taken with a view to the dissolution of the operator

(c) In any other case:

• the death of any of the named operators (where the operator consists of more than one named individual);
• any change in the operator’s name(s) or address(es); and
• any steps taken with a view to the operator, or any one of them, going into bankruptcy, entering into a composition or arrangement with creditors, or, in the case of them being in a partnership, dissolving the partnership.

4.3.4 Where the operator proposes to make a change in the nature of the activity by increasing the concentration of, or the addition of, or allowing the introduction of, a substance to the activity to an extent that the operator considers could have a significant adverse environmental effect on the receiving waters, and the change is not permitted by emission limits specified within these standard rules or the subject of an application for approval under the EP Regulations or under the terms of these standard rules:

(a) the Environment Agency shall be notified in writing at least 14 days before the increase or addition or allowing the introduction; and

(b) the notification shall contain a description of the proposed change.

4.4 Interpretation

4.4.1 In these standard rules the expressions listed below shall have the meanings given.

4.4.2 In these standard rules references to reports and notifications mean written reports and notifications, except where reference is made to notification being made “as soon as reasonably practicable”, in which case it may be provided by telephone.

“Accident” means an accident that may result in pollution.

“Ancient woodland” means any area that has been wooded continuously since at least 1600 AD, including ancient semi-natural woodland and plantations on ancient woodland sites.

“Annually” means once every year.

“Application” means the application for this permit, together with any additional information supplied by the operator as part of the application and any response to a notice served under Schedule 5 to the EP Regulations.

“Appropriate measures” for the purposes of the emission of substances not controlled by emission limits condition (condition 3.2.1) do not require the operator to undertake treatment to a level beyond that specified in condition 2.1.1, or to carry out routine monitoring for substances not controlled by emission limits.

“Biological SSSI” means for the purpose of these standard rules either:

(a) a SSSI which has been designated due to the presence of flora or fauna.

(b) a SSSI that contains surface water or springs that can provide habitat for flora or fauna.

“Boundary of the premises” means the general boundary as shown on the registered title deeds, under section 60(1) of the Land Registration Act 2002.

“BS 12566” means BS EN 12566-3:2005 “Small wastewater treatment systems for up to 50 PT. Packaged and/or site assembled domestic wastewater treatment plants” (ISBN: 0 580 47444 5 Publication Date: 15th Feb 2006).

“BS 6297” means BS 6297:2007+A1:2008 “Code of practice for the design and installation of drainage fields for use in wastewater treatment” (ISBN: 978 0 580 64038 4 Publication Date: 31st December 2007).

“Chemical dosing” means the addition of chemicals specifically to enhance the sewage treatment process, either passively or actively. For example, the additional of chemicals to reduce the level of certain pollutants, control odours or aid sludge settlement.

“Domestic sewage” means waste water from residential settlements and services which originates predominantly from the human metabolism and from household activities.

‘Electrocoagulation’ means a process that involves the in-situ generation of coagulant agents through the dissolution of sacrificial electrodes under a direct current and the subsequent removal of suspended particles and pollutants from the effluent.

“Emissions of substances not controlled by emission limits” means emissions of substances to air, water or land from the permitted activities, which are not controlled by an emission limit.

“Emissions to land” includes emissions to groundwater.

“EP Regulations” means The Environmental Permitting (England and Wales) Regulations SI 2016 No.1154 and words and expressions used in this permit which are also used in the Regulations have the same meanings as in those Regulations.

“European site” means a European site within the meaning of Regulation 8 of the Conservation of Habitats and Species Regulations 2017, or a site referred to in the National Planning Policy Framework 2024 as requiring the same assessment as a European site. 

“Every 12 months” means a rolling 12 months starting from the time of first operation of the sewage treatment system.

“Existing Discharge” means a discharge that was in place before 2 October 2023.

“Flows and Loads” means the version of “Flows and Loads – Sizing Criteria, Treatment Capacity for Small Wastewater Treatment Systems (Package Plants)” published by British Water (ISBN: 978-1-903481-10-3) applicable at the date of issue of this permit.

“Groundwater” means all water, which is below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil.

“Groundwater Source Protection Zone 1” means a zone:

(a) within 50 metres of a point at which water is abstracted for domestic or food production purposes from any underground strata, or

(b) defined by a 50-day travel time for groundwater to reach a groundwater abstraction point that is used to supply water for domestic or food production purposes, whichever is larger.

“Local Nature Reserve” means an area designated by a local authority under the National Parks and Access to the Countryside Act 1949.

“Local Wildlife Site” means an area designated locally for its nature conservation value.

“Marine Conservation Zone” means a Marine Conservation Zone as designated under the Marine and Coastal Access Act 2009.

“National Nature Reserve” means an area designated by Natural England under the National Parks and Access to the Countryside Act 1949, as amended by the Wildlife and Countryside Act 1981.

“Pollution” means the direct or indirect introduction, as a result of human activity, of substances, heat or biological entities or micro-organisms into air, water or land which may:

(a) be harmful to human health or the quality of aquatic ecosystems or terrestrial ecosystems directly depending on aquatic ecosystems,

(b) result in damage to material property, or

(c) impair or interfere with amenities or other legitimate uses of the environment.

“Principal aquifer” means geological strata which:

(a) exhibit a high intergranular or fracture permeability, and

(b) provide a high level of water storage and support water supply or base flow to rivers, lakes and wetlands on a strategic scale.

“Protected species and habitats” mean species and habitats that may be of principal importance, as listed in Section 41 of the Natural Environment and Rural Communities Act 2006 or protected under the Conservation of Habitats and Species Regulations 2017 or Wildlife and Countryside Act 1981, and that the Environment Agency considers to be at risk from the activity.

“quarter” means a calendar year quarter commencing on 1 January, 1 April, 1 July or 1 October.

“Ramsar site” means a wetland of international importance, designated under the Ramsar Convention (an international agreement signed in Ramsar, Iran, in 1971). It is government policy to treat Ramsar sites the same as European sites.

“Secondary A aquifer” means permeable strata capable of supporting water supplies at a local rather than strategic scale.

“Secondary B aquifer” means predominantly lower permeability strata including where they have, in part, the ability to store and yield limited amounts of groundwater by virtue of localised features such as fissures, thin permeable horizons or weathering.

“Secondary treatment” means treatment of the domestic sewage by a process generally involving biological treatment with a secondary settlement or other process. Note that “secondary treatment” under these rules is “appropriate treatment” for the purposes of the Regulations.

“Secondary undifferentiated rocks” means rock deposits or strata with variable permeability and storage properties which are not consistently a secondary A aquifer or secondary B aquifer.

“Significant pollution” means a category 1 or category 2 incident indicated by the Common Incident Classification Scheme (CICS).

“Site of Special Scientific Interest” means a Site of Special Scientific Interest as designated under the Wildlife and Countryside Act 1981 (as amended by the Countryside and Rights of Way Act 2000).

“Unproductive strata” means rock deposits or strata that are largely unable to provide usable water supplies and are unlikely to have surface water and wetland ecosystems dependent on them.

“Year” means calendar year ending 31 December.

End of standard rules.