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The private foul drain serving your property will drain to one of the following outfalls
Private (or shared) drainage systems draining to private cesspits, septic tanks or treatment plant or private pumping stations are your sole (or joint) responsibility.
It is not unusual for a home owner to be unaware that they in fact do drain into a cesspit or septic tank until a problem arises. Package treatment plant are usually easier to identify due to requirement for electical supply. So, assuming you suspect or know that your property does not drain to the public sewer, what's the difference between the various tanks in existence?
Package Treatment Plant - In circumstances where a Public Sewer is not a practicable option (either by gravity drain or via pumping station), a package treatment plant is the next preferred option in the Building Regulations hierarchy of preferred drainage solutions. A package treatment plant will accept raw sewage and produce an effluent quality suitable for discharge into a receiving watercourse, although they can discharge to soakaway where conditions are suitable. This is usually achieved by a combination of primary settlement and aerobic oxidation. A package treatment plant will require a power supply and requires servicing and de-sludging (usually annually).
Common problems with package treatment plant include mechanical and electrical breakdown, and blockage of the downstream pipework or soakaway. Blockages of downstream pipework are usually due to inadequate maintenance, resulting in the passage of sludge through the tank.
Septic Tank - A septic tank is by far the most common form of non mains sewerage that we encounter on a regular basis. A septic tank performs a basic primary treatment by primary sedimentation and anerobic digestion, and an aerobic oxidation secondary treatment of the sewage liquor leaving the tank as it flows through the downstream soakaway and into the surrounding ground. The effluent discharged from the outlet of a septic tank is unsuitable for discharge into watercourse or land drain. Because septic tanks only retain the sewage sludge left following primary sedimentation and anerobic digestion (the liquid passes through into the soakaway) they generally require less regular emptying than a cesspit (usually annually or every 6 months).
Most problems encountered with regard to septic tanks are due to bad smells caused by over use of chemicals or excessive grease preventing correct operation, or in some cases inadequate tank size. In addition, failure to regularly empty a tank can result in sludge blocking the voids in the soakaway and in the worst case requiring complete soakaway replacement. Furthermore, incorrectly connecting surface water drainage into a septic tank will almost certainly lead to problems as sludge is flushed through the tank and into the soakaway during heavy rainfall. A septic tank is designed to accept the low flows associated with domestic foul use, not significant storms.
Cesspit - A cesspit is merely a holding tank, holding all solids and liquid discharged by the property (or properties) discharging into it. A cesspit may be of brick, concrete or glass reinforced plastic construction. Generally, a cesspit requires frequent emptying (often monthly) due to the requirement to store all discharged sewage.
A cesspit is considered a last resort in the Building Regulations hierarchy of preferred drainage options. A cesspit would currently only be considered suitable in rare circumstances where mains drainage is unavailable (either by gravity or pumped system), no suitable receiving watercourse is available for a package treatment option, and the ground conditions are such that a septic tank is not suitable (not free draining or high water table).
Typical defects found in cesspits are structural issues resulting in leakage into the surrounding ground or ingress of ground water causing premature filling of the cesspit.
A correctly designed, installed and maintained septic tank or package treatment plant should years of trouble-free service. However, a defective system can lead to pollution, surcharging drains and a Public Health Nuisance.
If you are experiencing problems with your drainage tank system or pumping station please contact EDS for assistance. We can carry out percolation tests to establish if your existing system needs extending or we can undertake a full survey to see how your system can be improved.
Public Sewer :- Serving 2 or more properties, or (since 2011) serving solely your property but beyond your property boundary. Public Sewers are maintained by Water Companies, financed through your water and sewerage bills.
Private drain :- Serving your property or several properties but not ultimately draining into a public sewer. A private drain will ultimately outfall into either:-
i Individual use or Shared Package Treatment Plant
ii Individual use or Shared Septic Tank
iii Individual use or Shared Cesspit
iv In exceptional circumstances a watercourse