A general explanation of sewage tanks
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Most people do not need to worry where their sewage goes. However, houses outside the water authority main sewer areas have to have properly designed drainage systems. Three basic methods of sewage disposal are available: cesspools, septic tanks and package sewage treatment plants.
Water Authorities state the estimated amount of water used in a domestic household is:
140 litres (40 gallons) per person, per day including all children.
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Cesspools
A cesspool is a watertight tank, installed underground, for the storage of sewage. This tank will have an inlet drain run only. No treatment is involved. The cesspool should be sited at least 15 metres from habitable dwellings, preferably down slope and downwind. This type of system will require emptying as and when it fills. Taking in to consideration the above water authority calculation it is obvious as to the advantage of owning a large cesspool, the downfall being higher disposal costs for larger volumes.
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Septic Tanks
A septic tank system consists of the tank itself and drainage field or a water course discharge point. Raw sewage is fed to the tank, and settled sewage is discharged into a drainage field. Sludge settles through the system and has to be periodically removed. The drainage field typically consists of either a soak away or a system of sub-surface irrigation pipes which allow the effluent from the tank to percolate into the surrounding soil or ideally to an open water coarse, i.e. ditch, stream, river, lake etc . All septic tank outlets should legally have consent to discharge granted by one of the governing bodies listed below. Despite the simplicity of the operation and maintenance, it is generally recognised that proper care is rarely given to septic tanks. This is believed to be due to the costs of desludging and lack of knowledge of maintenance requirements. There are many different types of septic tank systems on the market, but generally they all undertake the same task.
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Modern Sewage Package Treatment Plants
Modern package plants are compact and those using the activated sludge process, produce less sludge than other methods. Primary settlement can also be eliminated and secondary sludge can be stored aerobically for long periods with negligible odour. These advantages over septic tanks and cesspools come at extra cost: initial outlay and maintenance costs are higher and power is required to operate the tanks. As the discharge is of a higher quality it is usually piped direct to a watercourse. This will generally require the consent of the Environment Agency before any work is undertaken. This method of disposal is often the only option available in areas with clay as soil porosity is not a concern.
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Aftercare of systems
Responsibility for satisfactory performance rests with the owner of the installation, and several control mechanisms exist to prevent and address problems of pollution, nuisance and health hazard. These mechanisms include the planning process, building control, environmental health legislation and regulatory function of the Environment Agency to protect water quality.
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Building Regulations
The installation or replacement of a sewage disposal system is subject to the requirements of the building regulations. An application must be submitted to the Local Authority prior to undertaking any work. This information is for your guidance only. Please contact your Building Control section for clarification regarding any building regulation matters. You are also advised to contact your Development Control section as planning permission may be required for your proposed work.