Septic Tanks & Cesspools
In some situations is it not possible to connect the drainage system of a property to a mains drainage system.
Septic Tanks and Cesspools can be effective ways of dealing with foul drainage provided they are managed correctly.
On average we each produce approximately 200 litres of waste water per day. Any drainage system has to have sufficient capacity to deal with these quantities, bearing in mind the number of people in the house.
What is a cesspool?
A cesspool or cesspit is a sealed underground storage tank which holds sewage until it is emptied out and disposed of. It may be brick or block construction or manufactured in steel or reinforced glass fibre and must have minimum capacity of 18,000 litres.
Where can it be sited?
A cesspool should be sited so that there is no risk of polluting water supplies and for preference as far as possible from any inhabited building.
Can it go wrong?
The tank can overflow or may leak. This is an offence under the 1936 Public Health Act. Also if it pollutes a water course, the Environment Agency may take legal action under the Water Resources Act 1991. This can lead up to a fine of £20,000 and 3 months imprisonment.
If it leaks a drainage engineer should be called out to remove the waste and clear up the sewage. The cause of the leak should be found and remedied.
What is a septic tank?
A septic tank is a type of biological sewage treatment system. Naturally occurring bacteria break down the solid matter, reducing its volume. The liquid flows out and is discharged via a drainage systems under the ground called a "soakaway" The accumulated solids need only be pumped out occasionally.
Like cesspools, they may be constructed in brick or blocks, although modern types are pre-formed in reinforced fibreglass.
Where can it be sited?
The tank should ideally be away from housing. Please contact Building Control for more specific advice.
What is a Package Treatment Plant (Biodisk/Biobubble)?
These also work by allowing the natural bacteria to break down the sewage. They are similar to septic tanks but usually include some means of stirring the sewage or adding air to the effluent so that the bacteria can break it down more effectively. Because of this they often require a power supply. They can provide a good quality effluent which is far easier to discharge. This means they are better suited to more environmentally sensitive areas and should be considered before a septic tank or cesspit.
Percolation Tests
Sometimes the surrounding ground is not suitable to allow effluent water to soak away. The soil may not be permeable if there is a lot of clay. Percolation tests need to be carried out to ensure that the water can be harmlessly disposed of from a septic tank or a similar installation. The tests should be carried out following BS6297: 1983 to determine the size of the soakaway. They must be sited 6 meters from a water course. It may not always be possible to install soakaways, soil conditions or other factors such as ground water levels may mean they would not be suitable. If so you will need to consider some other form of drainage. Before constructing soakaways you must obtain a "Consent to Discharge" from the Environment Agency, who will advise you on how to perform the percolation test.
How do I avoid problems?
Cesspools: Check the level in the tank regularly, do not let it overfill. Have it emptied at regular intervals: these will become more frequent if you install a dishwasher for instance
Septic tanks: Do not use excessive amounts of household detergents or bleaches, these upset the biological balance of the system. Do not overload the system by connecting rain or water drains to septic tanks or cesspools.
Package plants: Follow the manufactures instructions.
What if I have a problem?
Problems occur very rarely, but should be remedied as quickly as possible. If you are unable to find the problem and deal with it yourself, call out a specialist contractor. It may be necessary to have the tank emptied, so check the contractor can provide this service.
How can we Help?
We can provide advice on septic tanks and cesspools as well as investigate complaints of nuisance from drainage systems, leaking tanks or defective soakaways for instance. We can require the owner or owners to remedy the problem. Failure to do so can result in legal action against the person responsible under the Public Health or Building Acts.
For a copy of our Septic Tank, cesspools and other small treatment plants leaflet, please 
click here (235KB - PDF Help)
