Off-Grid wastewater treatment regulations in the UK (C) M Webb & InspectApediaRegulation of Septic Systems & Sewage Treatment Systems in the U.K.
Onsite / Off-Grid Wastewater Treatment Regulations Summary for the U.K.

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Onsite wastewater regulations in the U.K.

Summary of off-grid sewage treatment system regulations in the U.K. This article describes the three off-grid sewage handling & treatment options in the U.K., the requirement for an EN 12566 Certificate for larger treatment systems, the EN 12566 wastewater treatment system categories or types, limitations on or prohibitions on the use of cesspools, and regulations addressing the disposal of septage in the U.K. as well.

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Septic System & Off-Grid Onsite Septic System & Wastewater Treatment Regulations in the U.K.

Three Off-Grid Sewage System Options in the UK

Maureen Webb

In the UK there are three options for off-mains sewage systems:

  1. Septic Tank connected to an onsite soakaway bed or similar effluent disposal field
  2. Sewage Treatment Plant
  3. Cesspool (only in England and Wales as they are banned in Scotland)

1. Septic Tank Requirements for Off-Grid Wastewater Treatment in the UK

These are anerobic [anaerobic] settlement tanks that settle out the solids, forming  a sludge layer at the bottom of the tank and a floating crust on the top of the effluent. The liquid waste between these two layers is discharged to a soakaway drainfield, subject to Environment Agency or SEPA (in Scotland) permission. The majority of sites in the UK fail the mandatory

soakaway tests, making septic tank installations impossible in many areas.

2. UK Sewage Treatment Plant Requirements

These are aerobic tanks which treat the sewage effluent to a much higher standard of quality than a septic tank. The final effluent is allowed to be discharged directly to a watercourse or ditch, or to a soakaway drainfield, subject to Environment Agency or SEPA (in Scotland) permission.

3. Cesspools for Wastewater Collection in the UK

In the UK, cesspools are sealed underground holding tanks which offer no actual treatment of the sewage and have no effluent outlet.

Cesspools need to be emptied by tanker on a regular basis.

Cesspools are banned in Scotland as they are not sustainable and very expensive to operate.

Terminology note: Cesspool vs. holding tanks

In the U.S. a cesspool is an underground holding system that receives raw sewage and permits effluent to discharge into surrounding soils. Cesspools do not treat effluent because of their depth in the ground (lacking exposure of effluent to sufficient aerobic bacteria) and because of the limited volume of soil available to perform any treatment. See CESSPOOLS for details about these systems.

In the U.S. an "underground holding tank" is a water-tight sewage receiving tank that has no outlet whatsoever. Sewage holding tanks are generally not permitted by sanitary codes in the U.S. but local authorities may make exceptions such as for temporary use during construction or as "grandfathered" for certain facilities located adjacent to rivers, streams, or other bodies of water.

UK Septic System Rules and Regulations - EN 12566 Certification

All septic tanks and sewage treatment plants up to 50 persons must be registered and permitted in the UK. The Environment Agency operates the registration scheme and issues their Permits and Exemptions. In order to qualify for this acceptance, the systems must have an EN 12566 Certificate under the EPP2 (Environmental Permitting Programme Phase 2) regulations.

The EN 12566 certificate ensures that the tank has been structurally tested for strength and water-tightness and, in the case of sewage treatment plants, performance tested for water quality for 38 weeks at an independent EN Test Centre.

Cesspools must have been structurally tested for strength and be water-tight. They must also have a high level alarm.
From July 1st 2013, all tanks will need to be CE marked in addition to the above under the Construction Products Directive. In order to have the CE mark, the tanks must have an EN 12566 Certificate.

There are various EN 12566 categories as follows

[Click image to see an enlarged version]

Off-Grid wastewater treatment regulations in the UK (C) M Webb & InspectApedia

Building Regulations - relevant to sewage treatment plants and Septic Tanks in the U.K.

The Building Regulations 2000 - Drainage and Waste Disposal 2002 edition Part H-H2 Package Sewage treatment Works

The main provisions of the UK Sewage Treatment Plant Regulations

  • The Sewage Treatment Plant must be sited more than 7m from habitable property
  • The soakaway must be a minimum of 10 metres from a watercourse, 15 metres from a building, 2 metres from a boundary and 50 metres from a borehole or spring.
  • The soakaway must be designed to BS6297: 2007 and all percolation test results must be submitted. 
  • The discharge point shall be more than 10m from habitable property
  • If the discharge is to a soak away a sampling chamber must be provided before the soak away.
  • Soakaway drains must be constructed in the aerobic soil layer, i.e. within 700mm. of ground level

Regulation of the Emptying Septic Tanks and Sewage Plants in the U.K.

Septic Tanks and Sewage Treatment Plants can ONLY be emptied by licenced waste disposal companies, NOT by the local farmer with his slurry tanker.

It is highly illegal for anyone, other than a licensed waste disposal contractor to empty and dispose of all effluent from septic tanks and sewage plants.  The effluent must be taken to fully recognised and licensed sewerage treatment works. The regulated water companies operate these works.  It cannot be spread onto farmland.

Maureen Webb is a technical designer at WTE, Ltd., WTE designs, manufactures, supplies, installs and maintains all makes of sewage treatment plant including non-electric onsite wastewater treatment systems, septic tanks, cesspits, septic tank conversion units and pumping stations for both domestic and commercial applications, worldwide. Prices start from£1520 + VAT for full sewage treatment systems. We also are specialists in water filtration. For more details about WTE see the Company's website

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. 

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