Sewage Treatment System Options and Costs

Off-Mains Sewage Treatment Options




Cesspool is an enormous, fully sealed underground wastewater holding tank having only an inlet and no outlet. A cesspool is designed to hold all sewage and wastewater effluent and does not carry out any treatment of the sewage whatsoever. It is also sometimes refered to as a Cesspit.

Many people also to refer to their septic tank as a "Cesspit". You MAY have a cesspool or it may be a septic tank. If it has an outlet, irrespective of the size of the tank, it is a septic tank, not a cesspool.

  • A cesspool (cesspit) simply stores sewage and can only be emptied via a suction tanker.
  • The installation cost and annual running cost of a cesspool is prohibitive.
  • Cesspool units should only be installed as a last resort where a septic tank or treatment plant would not be possible, due to the lack of a watercourse, high winter water table, installation in a Groundwater Source Protection Zone, or the wrong type of soil for a Drainage Field to be installed.
  • Running costs for a family of 4 are about £7000 to £9000/year

We always consider the options that are available to your site and we can give a report and quotation for the preferred system.

Rainwater must be kept out of all sewage systems. 


Septic Tanks

Crystal Tanks - New Septic Tank pic

Septic Tank Systems used to be the common method of treating sewage in rural areas. They are now only usually acceptable for small-scale developments up to 15 persons and are banned from use in large areas of the UK.
They consist of a holding tank which partly breaks down the solids by anaerobic bacteria before discharging the liquid effluent through the outlet pipe into a septic drainfield soakaway. Septic tank effluent contains 70% of the original pollutants that are in the raw sewage.
Unfortunately, the effluent they produce is very polluting and can ONLY be discharged into a septic drainage soakaway, if the ground conditions allow.
  • The soil must be able to soak away the required volume.  Clay soils will NOT support soakaways.
  • The water table or bedrock MUST NOT rise to within 1 metre of the bottom of the soakaway gravel under the pipe at any time. This means that your water table must never rise to within 2 metres of ground level.
  • The site must not be in an E.A. Inner Groundwater Source Protection Zone.  Ring Crystal Tanks to determine this.
The septic drainage soakaway alone usually costs between £4000 and £12000 to construct.  You cannot discharge to a watercourse from a septic tank, nor can you allow the effluent to leak into a watercourse as the fines are enormous.
Any septic tank that does discharged into a ditch or watercourse MUST be replaced by a sewage treatment plant as soon as possible, or at point of sale if the property is sold.
Sewage Treatment Plants
Vortex sewage treatment plant installed for a house
Sewage treatment plants have replaced septic tanks. They clean the wastewater to a high standard and the effluent can be discharged either to a soakaway, if the ground conditions are suitable, OR to a watercourse, as long as you conform with the General Binding Rules of the Environment Agency.  The effluent is non-polluting if the plant is used and maintained correctly.

Typical installation costs are between £6000 and £12,000, depending on the type of plant and the ground conditions of the site.