Last updated: September 2026
Installing a septic tank or sewage treatment plant brings you into contact with several sets of rules at once, and one of the questions we hear most often is whether planning permission is needed. In most cases it is not. Building Regulations approval, on the other hand, almost always is, and there are a few other consents that can apply depending on where the property is and where the water goes.
This guide explains which permissions apply, when they apply and how to go about them, based on the current guidance for England and on the installations we carry out across Surrey, Sussex and Kent.
Do You Need Planning Permission for a Septic Tank or Sewage Treatment Plant?
For most homes, installing a new septic tank or treatment plant, or replacing an existing one, does not need planning permission. Domestic drainage of this kind is normally treated as permitted development under the Town and Country Planning (General Permitted Development) (England) Order 2015, provided the usual conditions are met. There are exceptions, and they are worth checking before any work starts.
Conservation Areas, National Parks and National Landscapes
Permitted development rights are more limited in a conservation area, a national park or a National Landscape, the designation that replaced Areas of Outstanding Natural Beauty. Large parts of the High Weald and the Surrey Hills fall into this category. Speak to the local planning authority before proceeding, because an application may be required.
Listed Buildings
If the property is listed, drainage works within its curtilage may need listed building consent even though they are underground. The same caution applies to scheduled monuments.
Discharges to a Main River
Where the treated effluent will discharge to a main river rather than an ordinary watercourse or a drainage field, a flood risk activity permit from the Environment Agency is needed. This is separate from planning permission.
Agricultural Land
Installations on agricultural land can fall under different rules. Check with the local authority planning department before committing to a design.
Building Regulations Approval: Always Required
Whether or not planning permission is needed, every new septic tank or treatment plant installation in England needs Building Regulations approval under Part H, which covers drainage and waste disposal. The approval is handled by the local authority building control team or by a registered building control approver in the private sector.
What Part H Requires
Part H sets the standards the system has to meet. The system must be adequate for the household it serves, the drainage field must be sized from the results of a percolation test, the tank must be built to the relevant British Standard, which is BS EN 12566-1 for septic tanks and BS EN 12566-3 for package treatment plants, the installation must not pollute any water source, and any electrical work for a treatment plant must meet the relevant electrical safety standards.
How to Apply
Your installer will normally make the application for you. It involves submitting a drainage design and site plan to building control with the fee, which is usually £200 to £400 for a domestic installation, and the inspector then visits at key stages of the excavation and installation. Country Drainage handles this as part of every installation we carry out.
The General Binding Rules: Your Environmental Obligation
Alongside planning and Building Regulations, the system must meet the General Binding Rules under the Environmental Permitting Regulations. These rules govern the environmental performance of the system and decide whether an Environment Agency permit is needed. A domestic system serving 10 people or fewer, with the correct discharge route, suitable ground and adequate capacity, does not need a permit. A system that cannot meet the rules needs either changing or an individual permit. Our guide to the General Binding Rules covers the detail.
Do You Need to Notify Your Water Company?
If the treated effluent will discharge to a surface water drain that belongs to a water company rather than to a ditch or watercourse, tell the water company. They may set conditions or ask for a formal consent for the discharge.
Neighbours and Boundaries
We recommend keeping a drainage field at least 3 metres from any boundary. That is a practical rule for maintenance access and to avoid disputes rather than a fixed legal minimum. It is also worth thinking about how the drainage field could affect neighbouring land in terms of odour or groundwater flow, particularly on sloping sites.
Replacing an Existing System
Replacing a septic tank or treatment plant in the same position with a similar system is even less likely to need planning permission. Building Regulations approval is still mandatory, and the new system must meet the current General Binding Rules. A non-compliant septic tank cannot simply be swapped for another non-compliant septic tank.
Buying a Property with Off-Mains Drainage
The buyer’s solicitor will investigate the drainage arrangements for any property that is not on mains sewerage. A non-compliant system, such as a septic tank discharging to a surface water drain, will be flagged in the searches and may become a condition of the sale or need putting right before completion. Ask the seller for the drainage compliance record, percolation test results and the Building Regulations approval for the existing system. If they cannot produce them, a drainage survey before exchange of contracts is money well spent.
How Country Drainage Can Help
The planning, Building Regulations and environmental rules can look daunting when they are all set out together, but in practice we deal with them every week. Country Drainage handles the whole process for septic tank and sewage treatment plant installations across Surrey, Sussex and Kent, including the site survey, the percolation test, the Building Regulations application and the installation itself. Contact us for a free initial consultation.
Frequently Asked Questions
Can I install a septic tank under a driveway?
Usually yes, provided the installation meets the Building Regulations requirements for cover depth and the tank is specified to take the load. We try to keep the inlet and outlet pipework away from the driveway where we can, and you need to be sure the tanker can still reach the tank for emptying.
How close can a septic tank or drainage field be to a house?
There is no statutory minimum distance from the house to the tank, but the tank should sit where groundwater cannot get into the foundations and where the pipework can fall properly. We generally recommend at least 3 to 4 metres. Drainage fields must be at least 50 metres from any well or borehole used for drinking water and 10 metres from any watercourse.
Do I need Building Regulations approval for a replacement septic tank in the same location?
Yes. A like-for-like replacement still needs approval, and the new tank must meet current British Standards and the current Part H requirements. For an experienced installer it is a routine part of the job.