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The private foul drain serving your property will drain to one of the following outfalls:
In circumstances where a Public Sewer is not a reasonable option (either by gravity drain or pumped rising main), 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.
A septic tank is by far the most common form of non mains sewerage that we encounter. A septic tank performs a basic primary treatment and a 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. Septic tanks only retain the sewage sludge left following primary treatment (the liquid passes through into the soakaway). Consequently, they require less regular emptying than a cesspit (usually annually or every 6 months). we would always recommed a percolation test prior to installing a septic tank.
Problems encountered with regard to septic tanks include bad smells caused by over use of chemicals or excessive grease, or sludge blocking the voids in the soakaway due to failure to regularly empty the tank (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.
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 today only be considered suitable on rare occasions 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 system 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 if and how your system could be improved.
A surface water separator or interceptor is designed to intercept surface water runoff from paved areas likely to be subject to oil or fuel and to separate the oil from the water, before the water is discharged to a receiving watercourse or combined sewer. They must be sized according to the impermeable area drained and the exact design will depend on the level of risk of pollution and the nature of the outfall. Separators can have alarms, telemetry and automatic shut off devices depending on their age, They can be designed to intercept all the surface water runoff or a percentage of it in low risk, low sensitivity areas.
Separators (or interceptors) should be maintained with a frequency often enough to ensure oil and silt does not build to a level where it can be passed downstream with insufficient treatment. This can vary significantly depending on the site conditions, but annual maintenance is typical.
EDS can carry out one off maintenance, assess existing systems and provide a scheduled mainenance plan, or design and install a completely new separator to suit site conditions. We are experienced in difficult access conditions and have extensive experience of maintaining and installing separator systems in the busiest of retail and commercial situations.
It is not unusual for a client 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?
Public Sewer :- (Serving 2 or more properties, or serving solely your property but beyond your property boundary). Public Sewers are maintained by Water Conpanies, 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 foul 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