Discharge to Surface Water – Rules and Regulations

Any sewage discharge to surface water (rivers/streams) must first be treated by an onsite wastewater treatment plant to prevent pollution. This article highlights the current rules and regulations for any systems with wastewater discharge to surface water in the UK.

Septic tanks with discharge to surface water

Septic tanks that discharge directly to surface water are no longer permitted. Therefore they must be replaced or upgraded by January 1st, 2020 or if the property is being sold before then. If a septic tank is found causing pollution to surface water, it must be replaced or upgraded as soon as possible. Alternatively, there is the option to install a drainage field to direct the discharge to ground instead.

In exceptional circumstances, a permit may be granted by the Environment Agency [EA] to allow a septic tank to discharge to surface water.

If you are upgrading your septic tank using a conversion unit you’ll need a permit. In addition to that, it will be up to you to prove that the outgoing wastewater meets the current standards.

If a septic tank or treatment plant is no longer in use, it must be properly decommissioned.

Wastewater systems with discharge to surface water before 31 December 2014

New rules came into force on January 1st, 2015. We refer to systems installed with a discharge to surface water before then as existing systems with existing discharge.

For these systems, the British Standards that were in place at the time of installation must be met. These include:

  • a CE mark
  • a certificate of compliance with a British Standard in the system documentation/manual
  • appears on British Water’s list of approved equipment

For systems installed before 1983, there were no standards in place.

New wastewater treatment plants with discharge to surface water

We refer to any wastewater treatment plant installed on or after 1st January 2015 as a new system producing new discharge.

Standards and Regulations for New Systems

For new systems, the current relevant British Standards are:

  • BS EN 12566 for small sewage treatment plants


  • BS 6297:2007 for drainage fields

Make sure the system you plan to install complies with these regulations before you install it.

Capacity of the System

As per the Code of Practice set down by British Water for Flows and Loads, the system must be large enough to support the maximum amount of incoming wastewater. In addition, you’ll need a permit if the maximum daily volume of wastewater increases by 5000 litres or more, for example, if you are extending your property or adding on extra buildings.

Proper Installation of the System

When installing a system with discharge to surface water, make sure you are aware of the manufacturer’s technical prerequisites and that you carefully follow the instructions given. This ensures that the wastewater is correctly treated, the environment is protected and that health and safety standards are maintained.

Regular Maintenance

Most new systems require annual cleaning or otherwise, this is usually specified in the manufacturer’s guidelines. Cleaning involves the removal of solid waste (sludge) by a registered and certified waste carrier. Make sure you follow any maintenance guidelines set out in the manufacturer’s guidebook. If your system is faulty and needs repairing, hire an accredited service engineer. Signs of a faulty system include smells, leaks, cracks or blockages.

Change of Ownership

If you are selling a property that has a wastewater discharge to surface water, you must inform the new owner in writing of it. Therefore include details such as the location of the component parts of the system, maintenance required and any changes made to the system.

Installing a New Wastewater Treatment Plant with Discharge to Surface Water as of 1st January 2015

You must have planning permission and Building Regulations approval before installing any system with discharge to surface water.

If the property is within 30m of a public sewer, the EA won’t grant permission for any new discharge to surface water. If the sewer is inaccessible, the EA may grant a permit the system.

A permit is required if discharge to surface water is to or within 500m of a designated sensitive area. Contact the EA for information on or to find out the location of designated sensitive areas. Further information on permits and how to apply is available here.

With any new discharge to surface water, you must direct it to a  source of continuously flowing water. If this isn’t possible, you could install a partial drainage field (seasonal soakway). This is where the discharge is directed to when the flow of surface water is low. Bear in mind that the system must be installed within 10m of the edge of the surface water and cannot be used with a septic tank.

Finally, if you want to install a new system with discharge to surface water but there’s a problem with particular regulation, contact the EA for advice. Don’t, however, just go ahead and install it anyway. The EA carry out routine inspections on any system with discharge to surface water so make sure it does meet the current regulations.

In conclusion, if the EA find that the discharge to surface water from your new system is below standard you will be liable for penalties and fees so it’s well worth sourcing a system from a reputable supplier.

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