In some situations it is not possible to connect the drainage system of a property to a mains drainage system. Most commonly non-mains drainage is found in rural areas. It is effective if correctly managed. 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.
The main types of non-mains drainage are:
• Septic tanks
• Package treatment plants
A septic tank is effectively a mini-sewerage system. Sewage is stored in a watertight two or three chamber tank where bacteria break down solid matter to one third of its original volume. Settled solids are retained and a clear liquid flows out via land drainage, a soakaway.
Older septic tanks may be constructed in brick or blocks, although modern types are pre-formed in reinforced fibreglass.
Installing a new septic tank requires permission from building control and a consent to discharge from the Environment Agency, telephone number 08708 506506. Septic tanks should be sited not less than 10 m from any ditch, drain or watercourse, not less than 50 m from any well or borehole (this distance may be increased for site specific conditions) and preferably not closer than 15 m to any dwelling.
Septic tanks should be emptied annually to prevent a built up of sludge. We do not empty septic tanks. Should you need your tank emptying please contact a private contractor, registered with the Environment Agency for the carriage of effluent waste. They are listed in trade directories such as the yellow pages.
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.
Septic tanks and small package treatment plants should be registered with the Environment Agency. The deadline for discharges to ground to be registered is 31st December 2011.
Further guidance on registering non-mains drainage systems in Wales can be found at https://naturalresources.wales/permits-and-permissions/water-discharges-and-septic-tanks/register-your-septic-tank-or-small-sewage-treatment-plant/?lang=en
A cesspool or cesspit is a watertight underground tank and under current standards new cesspools must have a minimum capacity of 18,000 litres. Older cesspools are lined with brick or concrete, and more modern ones with plastics, polythene or steel. Foul water is stored until the time of disposal.
A cesspool should be sited so that there is no risk of polluting water supplies, not less than 10 m from a watercourse and preferably not closer than 15 m to any dwelling.
Cesspools should be emptied as required. A cesspool must be pumped out or otherwise emptied by a competent contractor. It is an offence for anyone other than a competent contractor to do this. Check the level in the tank regularly, do not let it overfill. The installation of a warning device is recommended. Have it emptied at regular intervals: these will become more frequent if you install a dishwasher for instance.
Like septic tanks package treatment plants work by allowing the natural bacteria to break down the sewage. They 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.
Package treatment plants can usually discharge to a watercourse, however a discharge consent will be required from the Environment Agency.
Follow the manufactures instructions on desludging and maintenance. Check the manufacturer’s instructions on the use of cleaning materials, such as bleach, and do not use the drains as a means of disposal for chemicals, oils, solvents or paint brush cleaning fluids. These materials can impair the treatment process and may even damage the plant. Care should be taken to prevent the discharge of grease to the treatment plant as this may also reduce the efficiency of the treatment process.
Problems occur very rarely provided the non-mains drainage system is properly maintained and used according to manufacturer’s instructions.
It is an offence under the Public Health Act 1936 to permit a cesspool to leak or overflow. The owner or occupier of premises with such a system should ensure the tank is watertight and emptied regularly by a licensed contractor who will dispose of the contents at a sewage treatment works.
This Act also applies to septic tanks that are not properly maintained and produce an effluent that is prejudicial to health or a nuisance.
If a non-mains drainage system pollutes a water course, the Environment Agency may take legal action under the Water Resources Act 1991. This can incur a fine of up to £20,000 and up to 3 months imprisonment.
If a non-mains drainage system 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.
Public health will investigate complaints of nuisance from drainage systems, leaking tanks or defective soakaways for instance. They 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 Act 1936 or Environmental Protection Act 1990.