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Environment Agency General Building Rules for septic tanks/ sewage treatment systems

As of 1 January 2015, the Environment Agency General Binding Rules have come into force, meaning that all sewage discharges must comply, including both existing and new systems. 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’.

It is your responsibility, as the owner of the septic tank or sewage treatment system, to ensure you comply with these rules.

Importantly, if you have a septic tank then this must not discharge into any watercourse or ditch. You must use a septic tank or small sewage treatment plant to treat the sewage and then discharge the effluent (treated liquid) to ground via a drainage field.  If your existing septic tank does currently discharge to surface water, you will need to replace or upgrade it by 1 January 2020 or when you sell your property if before this date.

If you have a sewage treatment system with certification to EN12566-3, this means it is legal and safe to discharge into a ditch, stream or other watercourse. If you cannot access a watercourse, you are able to discharge via a drainage field into the ground.

Rules for existing and new discharges

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

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

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 documents that came with your system has a certificate of compliance with a British Standard – check with your installer if you’re unsure
  • it’s on British Water’s list of approved equipment

If there were no British Standards in place when your treatment system was installed (that is before 1983) you do not need to do anything else to meet this requirement.

Your treatment system must be installed correctly and have enough capacity

Your treatment system must be large enough to handle the maximum amount of sewage it will need to treat. For new installations of both septic tanks and sewage treatment systems, you must check with the installer that it meets the sizing requirements in British Water’s Flows and Loads 4.

If the amount of sewage the system needs to treat increases (for example, because you’ve extended your property or connected another property) you must ensure 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 2 cubic metres (2,000 litres) a day (for systems discharging to ground) and 5 cubic metres (5,000 litres) a day (for systems discharging to surface water).

Your treatment system must be installed in line with the manufacturer’s specification in the manual that came with the equipment. Using an accredited installer will give peace of mind that this has been done correctly, and will help to avoid problems in the future.

Have your treatment system regularly emptied and maintained

You must have your septic tank or sewage treatment system emptied (de-sludged) before it exceeds the maximum capacity. As a minimum, we recommend de-sludging annually or in line with the manufacturer’s instructions.

You must ensure that you use a registered waste carrier to dispose of the sludge. A registered waste carrier will provide a copy of the Waste Transfer Note to certify it has been disposed of correctly.

You must also keep your system properly maintained, and repair or replace it if it isn’t in good working order. The best method of addressing issues is to get your system serviced annually by a qualified engineer. They will be able to check for any leaks, cracks, blockages, drainage problems, smells or failed parts.

If you sell your property

If you sell your property, you must tell the new owner in writing that a small sewage discharge is in place. When you tell the new owner about the septic tank/treatment system, include the following:


  • 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


If you stop using your septic tank/treatment system

You must remove anything that could cause pollution (remaining sludge etc.) when you stop using a septic tank or sewage treatment system.

This doesn’t apply if you only stop using the equipment temporarily, for example if you go on holidays or your property is empty for a short period of time.

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

Rules for discharges in a groundwater source protection zone 1 (SPZ1)

A groundwater SPZ1 can be either:

  • the area around a commercial water supply (used for drinking water or food production)
  • shown on the map of protected zones – check if your discharge is in the inner zone (zone 1) or ask the Environment Agency
  • any area within 50m 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

You must apply for a permit if you have an existing discharge or are planning to start a new discharge to the ground in a SPZ1. The permit costs £125. A permit will include additional conditions to the general binding rules.

The Environment Agency will grant the permit if there’s:

  • no evidence of pollution
  • the risk of pollution is acceptable

If there is evidence of pollution or the risk of pollution is unacceptable the Environment Agency will ask you to make changes to your system and may issue a permit with improvement conditions.

The Environment Agency regularly checks:

  • surface and groundwater quality
  • permit compliance

If they find your system may be causing pollution to surface or groundwater they will contact you to discuss the issues. This may result in your permit being reviewed or revoked.

Additional rules for new discharges from 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 septic tank or small sewage treatment plant on or after 1 January 2015
  • had a discharge to a surface water before 1 January 2015 which you now want to change to discharge to ground, or the other way round
  • had a discharge to ground before 1 January 2015 and you want to install a new drainage field more than 10 metres away from the existing one

These are called new discharges.

Check if there’s a public sewer nearby

If any part of the building your treatment system serves is within 30 metres of a public sewer, the Environment Agency will not allow you to start a new discharge from a septic tank or small 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, so 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 authority.

If there is a good reason why you can’t connect to the sewer (for example, if 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 small sewage treatment plant instead.

Building regulations and planning approval

You must have planning permission and Building Regulations approval if you have, or are planning to install, a new septic tank or small sewage treatment plant.

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 ground in or near a designated sensitive area, you must apply for a permit. You will need a permit if the new discharge will be in an ancient woodland or in or within 50 metres of any:

  • special areas of conservation
  • special protection areas
  • Ramsar sites
  • biological sites of special scientific interest

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 (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.

Read more on the General Binding Rules: small sewagedischarge to the ground

Read more on the General Binding Rules: small sewage discharge to a surfacewater

We can provide advice and assistance with the application process for any Environment Agency permits/exemptions – contact us on 01388 537050 for more information.