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Back to Basics - 06 February 2008

Mains or Off-Mains Drainage

The majority of houses in the UK are linked up to a public sewer pipe.  You pull the plug, flush the toilet, pay the bill and have little worry about it.  This is Mains Drainage.

In rural areas many homes & willages are self-contained; the combined waste ending up in a local Cesspool, Septic Tank or Treatment Plant.  This has no connection to the public sewer system and is known as Off-Mains.

Cesspools

A Cesspool is simply a single-chamber storage tank with no outlet.  The tank is usually very large (as it has to contain all waste water & sewage) and is often made from concrete, brick or GRP.  The only way to dispose of the waste is by hiring a licenced sewage contractor to remove the sewage for off-site disposal.

The use of Cesspools is no longer an option in most instances.

Septic Tanks

A Septic Tank is a multi-chamber storage tank allowing liquid and solid waste to separate.  The liquid is allowed to flow out of the tank and be disposed of separately.  Firstly the sewage enters a settlement chamber, allowing solid waste (sludge) to sink and the liquid to rise to the surface.  The surface liquid makes contact with oxygen and the organic matter starts to breakdown biologically.  This liquid still contains sewage but in small enough particles to be carried through the discharge outlet and into the ground (soakaway).

Basic Septic Tanks only partially treat sewage and discharge effluent of low quality. Many authorities in the UK prohibit their use.

More advanced products, like Biodiscs amd  Entec SuperSeptic treatment plant  offer a much higher level of effluent quality, but in all instances a Sewage Treatment Plant should be considered as the first option.

Septic Tanks may be installed (subject to consent) in applications where:

• Soil is of suitable porosity.
• Installation complies with Building Regulations (Approved Document H).
• The installation will not contaminate any ditch, stream or other watercourse.