Down the Plughole
If you have lived in a house in the country with private drainage for many years, then you will probably know all the niceties involved with sewage disposal. If however you are a town dweller with a dream of moving to the countryside, this article may be of interest.
In the town, the majority of houses are connected to the public main sewer via a private drain. The Local Authority will maintain the main sewer, but the individual householder is responsible for the private pipe connecting the house to the sewer.
The term "sewer" does not necessarily mean that effluent is carried through it. The farmland around Tenterden has any number of open sewers crossing it, but these are merely drainage ditches carrying surface water away from the surrounding land. "Sewage" means the actual effluent discharged from your house, which is then disposed of through the "sewerage" system.
The main methods of sewage disposal in rural areas are by septic tank or cesspool – there is a difference between them. A cesspool is a single watertight tank, installed underground for the storage of sewage. No treatment of the sewage takes place within the tank, which needs emptying at regular intervals (depending on how big the tank is and how many people occupy the house).
The Building Regulations prescribe that a notice should be fixed within a house, served by a private drainage system, with wording such as: "The foul drainage system from this property is served by a cesspool. The system should be emptied approximately every three months by a licensed contractor and inspected fortnightly for overflow. The owner is legally responsible to ensure the system does not cause pollution, a health hazard, or a nuisance." Not a lot of people know that.
A septic tank on the other hand, has two chambers and an overflow system. The waste solids sink to the bottom of the first tank and are broken down by bacterial activity (hence the need not to use biological washing powders). The liquefied sewage is then discharged into the second tank for further digestion, before it discharges through the overflow into a secondary system, which might be a leach (drainage) field, or into a stream or ditch. If the treated sewage does discharge into a watercourse, then a Consent to Discharge is required from the Environment Agency, who will check that the effluent has been sufficiently treated within the tank.
One of the most effective secondary treatments is where the waste water is "polished" through a reed bed system, such as that installed by Prince Charles at Highgrove; at the end of the treatment, the water is perfectly drinkable (although I have not tried it myself!).
More commonly installed these days are small sewage treatment plants (e.g. Klargester Biodisc). These are powered by electricity and treat effluent to a higher standard than septic tanks, so that the overflow can normally be allowed to discharge directly into a watercourse (a Consent from the Environment Agency will still be required). These plants need a steady flow of sewage to keep the micro-organisms alive and to operate efficiently, and therefore may not be suitable for holiday accommodation which is occupied on an irregular basis.
If you have any problems with your private drainage system, please do not contact me!
Published May 2010
