The majority of properties are connected to the mains drainage system and private drainage is becoming increasingly uncommon due to legislative intervention. Private drainage systems are designed to be relatively self-contained but will come with maintenance requirements and regulations that need to be adhered to and such systems are most commonly used by rural properties that are located a long distance away from public sewers.
There are two types of drainage: foul water drainage (which carries foul water from properties) and surface water drainage (which carries rainwater from hard surfaces).
If you connect to a mains drain, you will pay sewerage rates to the local water and sewerage company. A public sewer becomes vested in the local sewerage undertaker who will then cleanse and maintain the sewer and ensure it is emptied. If you have private drainage however, you will bear the costs of maintaining and emptying the same. Even if your septic tank or cesspit is on someone else’s land, you will be responsible for the maintenance of the system.
It is therefore advisable not to purchase a property unless you know what condition the private drainage system is in and it complies with the appropriate legislation (see below) as upgrading or replacing the same will be costly. When purchasing a property with private drainage, your conveyancer will raise any necessary enquiries in relation to the same at the time of your purchase to ensure you are properly advised and fully aware of the position. On the other hand, it is important that if you are selling a property which benefits from private drainage, that you have maintained the system and have complied with the various rules and regulations as if not, it could cause delays in the sale.
There are three main types of private drainage: septic tank; sewage treatment plant; cesspit, all of which are designed to store and process a property’s waste, allowing it either to be collected for waste disposal or discharged into a watercourse once purified.
Septic tank
Septic tanks separate liquid and solid effluent, discharging the wastewater into a drainage field or soakaway that treats and purifies the liquid. Any solid waste is disposed of by a registered waste collection service.
Septic tanks should be at least 7 metres away from any habitable parts of the building. They should also be located within 30 metres of an access point so that the tank can be emptied.
Under the General Binding Rules (see below), septic tanks are no longer permitted to discharge directly into a watercourse. If it does, you must replace or upgrade your system to be compliant. To replace the system you can either install a drainage field so that the waste water disperses into the ground or look to replace the septic tank with a sewage treatment plant. Any replacement must comply with the relevant standards and must be approved by planning and building regulations if applicable.
If the system discharges more than two cubic metres into the ground you will need to apply to the Environment Agency for a permit. In addition, the installation must be in accordance with the manufacturer’s installation specifications and the drainage field must be designed in accordance with BS6297:2007.
If you are selling a property, it is important to note that you cannot install a new drainage field if any part of the building the septic tank serves is within 30 metres of a public sewer. If this is the case, the property must be connected to the public sewer.
When you come to sell the property, you must inform the new owner in writing they are responsible for the septic tank discharge and include a full description of the system, its location and maintenance obligations.
The general binding rules state that if you are buying or selling a property with a septic tank that discharges directly into a watercourse you should agree with the buyer or seller who will be responsible for the replacement or upgrade of the existing treatment system. You should agree this as a condition of sale. If the septic tank does not discharge to a drainage field you should either connect to the mains sewer, install a drainage field or replace the septic tank with a small sewage treatment plant as soon as possible. The plans must be carried out within a reasonable timescale e.g. 12 months.
Sewage treatment plant
A sewage treatment plant is a system which treats the waste through internal processes and discharges effluent to a higher standard of cleanliness compared to septic tanks, allowing the waste to discharge straight to surface water sources once the water has been treated as it is then clean enough to discharge into a watercourse directly or a drainage field.
Sewage treatment plants must be EN12566-3 tested and approved. Any relevant planning permission and building regulations should be obtained if applicable. The discharge from the tank must be at least 10 metres from any water courses or buildings and if the plant needs electric to operate, it should be able to function without power for up to 6 hours or have a power supply that cannot be interrupted.
Cesspit
A cesspit is simply a tank that collects effluent without any in built treatment system. The waste therefore needs to be collected and disposed of regularly rather than being discharged.
Cesspits and cesspools should be at least 7 metres away from any habitable parts of the building and within 30 metres of an access point for emptying. The tank should have a minimum capacity of at least 18,000 litres for 2 users and should be increased by 6,800 for each additional user. Users are normally based on the number of bedrooms at the property + 2.
You should maintain and empty the cesspit regularly to ensure it does not leak or overflow. You will not however need a permit or to comply with the general binding rules unless the environment agency tells you otherwise. The environment agency can make you repair or replace your cesspit if it is in a poor condition. If your cesspit causes, pollution, this is breaking the law.
General Binding Rules
Many property owners are not aware that they must ensure their drainage system complies with regulations that have been introduced and are known as the General Binding Rules.
If you operate a septic tank or sewage treatment plant, you will need to comply with the regulations as the systems involve discharging waste water into the environment. Compliance is key particularly when you come to selling your house as any issues could cause delays.
If you operate a septic tank or small sewage treatment plant, you will not need a permit if you meet all of the General Binding Rules that apply to you. The General Binding Rules were introduced in 2015 and apply to homeowners who own new and existing off-grid drainage. The General Binding Rules are a term given to regulations that set minimum standards or conditions that apply. The rules are complex and full details can be found here: https://www.gov.uk/government/publications/small-sewage-discharges-in-england-the-general-binding-rules/general-binding-rules-for-small-sewage-discharges-ssds-with-effect-from-2-october-2023
If you do not meet the General Binding Rules, you may need to contact the sewerage undertaker to see if it is possible to connect into the foul sewer or upgrade your system so that it complies. If not, you can apply to the Environment Agency for a permit to discharge but this will be a “last resort” if you cannot change the system or connect into the mains sewer. If you do not comply with the general binding rules or obtain a permit, you will be breaking the law.
The rules vary for new and existing discharges. You are now no longer allowed to discharge from a septic tank into a watercourse or to any other type of soakaway stem other than a drainage field. In addition, new discharges should be connected to a mains sewer if possible and the Environment Agency decide it is reasonable to do so. This will be decided after considering how close you are to the public foul sewer, the costs of connecting the system, if there is anything in the landscape that would stop you connecting to the sewer and if it would have any environmental benefits. New systems should only be installed if its not reasonable to connect to a public foul sewer.
Planning permission/ Building Regulations
In addition to comply with the British Standards and General Binding Rules, you must also consider whether you need to obtain building regulations approval and planning permission when you install or upgrade your private drainage system.
You should always obtain building regulations approval. Planning permission is not always required but may be and so it is important to check.
If your property has private drainage, you will be responsible for maintaining an off-mains drainage system and ensuring it is in optimal working order in accordance with the general binding rules set out by the environment agency. Failure to do so will leave you personally liable and you could face a fine. The Environment Agency has enforced the rules through both criminal and civil sanctions to date, to ensure compliance.
If you already have a sewage system in place, you should check it meets the general binding rules, using this link : https://www.gov.uk/permits-you-need-for-septic-tanks/you-have-a-septic-tank-or-small-sewage-treatment-plant
Therefore, if you are thinking of buying/selling property, if the property has a private drainage system it is important to consider if the current system is compliant with the General Binding Rules and if not, consider whether a suitable upgrade or replacement is needed. A private drainage surveyor can be required to inspect and advise on the best option.
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