Managing sludge from non-mains systems
Source: gov.uk (2025-04-29)

How businesses in England can manage septic tank sludges and other wastes from non-mains domestic sewage systems.

Non-mains domestic sewage systems generate sludges and other wastes. These systems include:
- septic tanks
- small sewage treatment plants
- separator toilets
- cesspools
- chemical toilets
- portable sanitary toilets
These systems may be used by:
- householders who cannot connect to the main sewer
- holiday parks and camping sites
- marinas and lock sites
- construction sites
- festivals and show grounds
- allotments
- public spaces, car parks, visitor attractions, golf courses and other recreational sites
If your business takes this kind of waste, you must meet your duty of care requirements (https://www.gov.uk/dispose-business-commercial-waste) if you:
- collect it
- store it
- treat it
- recover it
- spread it to land (landspread it)
- dispose of it
Managing separator toilet waste

A separator toilet is like a septic tank. If it has been operated correctly, it will have produced a residual septic tank sludge and a liquid.

If the separator toilet does not separate out the waste liquids and solids, you must manage it as a cesspool waste.

The term ‘composting toilet’ is now widely used for various types of separator toilets.

Check if the solid material produced meets the description of a residual septic tank sludge given in this guidance.

If you are not sure about how to classify the solid material, you can contact the Environment Agency for advice.

Storing sludge from non-mains systems

Check if you can follow the Environment Agency’s regulatory position statement (RPS) Storing and treating chemical toilet waste: RPS 277 (https://www.gov.uk/government/publications/storing-and-treating-chemical-toilet-waste-rps-277). This RPS allows you to store:
- non-hazardous chemical toilet waste at a location controlled by the operator of a portable toilet hire business
- cesspool and septic tank waste at a location controlled by a tanker operator
- sewage from boats at a marina or lock site
You must apply for a permit (https://www.gov.uk/guidance/waste-environmental-permits) if you cannot meet the conditions of RPS 277.

If you are planning to store septic tank sludge at the place where it will be used under the Sludge (Use in Agriculture) Regulations, you must either:
- register an S3 waste exemption for storing sludge (https://www.gov.uk/guidance/waste-exemption-s3-storing-sludge)
- apply for a permit (https://www.gov.uk/guidance/waste-environmental-permits)
See the section of this guide on ‘Storing septic tank sludge for use in agriculture’.

Treating sludge from non-mains systems

You can treat or dispose of waste at an appropriately regulated facility. These include a:
- waste water treatment works
- waste management facility
The sludge you are treating, which is likely to be 20 03 04 ‘septic tank sludge’, may change its waste code and description after the waste treatment activity. Check the waste classification technical guidance (https://www.gov.uk/government/publications/waste-classification-technical-guidance) for the correct code to use.

Check if you can use the T21 waste exemption: recover waste at a waste water treatment works (https://www.gov.uk/guidance/waste-exemption-t21-recover-waste-at-a-waste-water-treatment-works). You must register this exemption. You must apply for a permit (https://www.gov.uk/guidance/waste-environmental-permits) if you cannot meet the conditions of the exemption.

You must only use the waste code and description 16 10 02 ‘cesspool waste and other sewage sludge’ if the sludges have been mixed with cesspool waste.

If you have registered the T21 exemption, check if you can follow Using waste codes for sludge materials: RPS 231 (https://www.gov.uk/government/publications/waste-codes-for-sewage-sludge-and-sludge-containing-other-materials-rps-231). This includes other waste types you can accept. You must be able to meet all of the conditions of the RPS.

Treating waste from portable separator toilets

Check if you can use the low risk waste position (LRWP) Treating solid waste from composting toilets: LRWP 90 (https://www.gov.uk/government/publications/low-risk-waste-positions-effluent-and-sludge/treating-solid-waste-from-composting-toilets-lrwp-90) for portable separator toilets. This allows you to treat the solid waste from portable toilets at the depot where the toilets were hired out from. You must be able to meet all the conditions.

Classifying sludge from non-mains systems

You must assess and classify waste using the waste classification technical guidance (https://www.gov.uk/government/publications/waste-classification-technical-guidance).

When classifying the waste, check if you can use:
- Replacing the use of ‘not otherwise specified’ waste codes: RPS 241 (https://www.gov.uk/government/publications/waste-codes-not-otherwise-specified-rps-241)
- Using waste codes for sludge materials: RPS 231 (https://www.gov.uk/government/publications/waste-codes-for-sewage-sludge-and-sludge-containing-other-materials-rps-231)
Spreading residual septic tank sludges to land used in agriculture

This section focusses on the use of septic tank sludge to agricultural land under the Sludge (Use in Agriculture) Regulations. Under the regulations ‘septic tank sludge’ means residual sludge from septic tanks and other similar installations for the treatment of sewage.

You can spread residual sludge from septic tanks or similar non-mains domestic systems directly to land used in agriculture under these regulations, if it is suitable for use.

You must apply for a permit (https://www.gov.uk/guidance/waste-environmental-permits) to spread septic tank sludges to land which is not used for agriculture, within the meaning of these regulations.

Wastes that are not suitable for agricultural land

You must not spread septic tank sludge to agricultural land if:
- it is not just sludge - modern septic tanks and package sewage treatment plants are usually completely emptied, so you may not just have the sludge from it
- it has been mixed with other waste in a collection tanker
You must manage these wastes as cesspool wastes.

You must not spread wastes direct to agricultural land from:
- cesspools
- chemical toilets
- toilets that do not separate wastes (non-separator toilets)
You may be able to treat these wastes so that they are suitable for use. See the section on ‘Treating sludge from non-mains systems’.

Storing septic tank sludge for use in agriculture

The storage of septic tank sludge at the place where it will be used for use under the Sludge (Use in Agriculture) Regulations is controlled by the Environmental Permitting Regulations.

Check if you can use the S3 waste exemption: storage of sludge (https://www.gov.uk/guidance/waste-exemption-s3-storing-sludge). This allows you to store up to 1,250 tonnes of sludge at the same place where it will be spread to land.

You must apply for a permit (https://www.gov.uk/guidance/waste-environmental-permits) if you cannot meet the conditions of the exemption.

You are responsible for registering the S3 waste exemption or having a permit, not the farmer or land manager.

If you have registered the S3 exemption, check if you can use Using waste codes for sludge materials: RPS 231 (https://www.gov.uk/government/publications/waste-codes-for-sewage-sludge-and-sludge-containing-other-materials-rps-231). This includes more waste types you can accept. You must be able to meet all the conditions of the RPS.

Spreading septic tank sludge to land used in agriculture

You can spread sludges from septic tanks and similar systems to land used in agriculture if you:
- have assessed that the sludge is suitable for use
- meet the relevant requirements of the Sludge (Use in Agriculture) Regulations
Land used for agriculture means land for growing commercial food crops and stock rearing.

Meeting the requirements of the Sludge (Use in Agriculture) Regulations

To comply with the requirements for spreading septic tank sludge under the Sludge (Use in Agriculture) Regulations, you must make sure that, after application to land:
- animals must not graze for 21 days
- forage crops must not be harvested for 21 days
- fruit and vegetable crops (which are grown in direct contact with the soil and normally eaten raw) must not be harvested for 10 months
The occupier of the land must make sure that any untreated sludge that was not injected into the soil is worked into the soil as soon as reasonably practical.

The Environment Agency recommends that you only use treated septic tank sludge. See the section on ‘Treating sludge from non-mains systems’.

The Environment Agency recommends that you consider using the Sewage sludge in agriculture: code of practice (https://www.gov.uk/government/publications/sewage-sludge-in-agriculture-code-of-practice).

Get advice

You can get advice about the environmental permit you may need (https://www.gov.uk/guidance/get-advice-before-you-apply-for-an-environmental-permit) for your activity.