Last updated: September 2026
The General Binding Rules are the conditions that govern how septic tanks and small sewage treatment plants must be installed, operated and maintained in England. If you own a property with off-mains drainage, or you are about to install a system, the rules are not optional. A system that falls outside them can lead to enforcement action by the Environment Agency and, in the worst case, the cost of a complete replacement.
This guide explains what the rules require, which systems they cover and what you need to do to stay compliant in 2026. It is based on the guidance published on GOV.UK and on the systems we survey every week across Surrey, Sussex and Kent.
What Are the General Binding Rules?
The General Binding Rules sit under the Environmental Permitting (England and Wales) Regulations 2016. They allow a small sewage discharge, meaning one serving a population equivalent of up to 10 people, to operate without an environmental permit, provided every one of the conditions is met.
If your system meets the rules you do not need to apply to the Environment Agency for anything. If it does not, you either change the system so that it complies, or you apply for an individual permit, which costs more and comes with monitoring conditions.
When Did the Current Rules Come Into Force?
The current rules took effect on 1 January 2020, replacing the 2010 version. The biggest change was the end of septic tanks discharging to surface water. Owners of those systems were required to replace or upgrade them by 1 January 2020, or earlier if the property changed hands. There was no later grace period. In 2026 a septic tank that still discharges to a ditch, stream or surface water drain is simply non-compliant, and it is one of the most common problems flagged during conveyancing on rural properties in the South East.
The Key Conditions for Septic Tanks
Discharge to Ground, Not Surface Water
A septic tank operating under the rules must discharge to a drainage field, where the effluent percolates through the soil and is treated by the bacteria in it. Discharge to a surface water drain, ditch, stream or river is not permitted. If that describes your tank, you need either a sewage treatment plant, a compliant drainage field if the ground allows one, or a permit.
Capacity of 10 People or Fewer
The system must serve a population equivalent of 10 or fewer. For a typical home that covers a house of up to four or five bedrooms. Larger properties, or several dwellings sharing one system, need a proper capacity calculation and may need a permit.
Correct Siting and Construction
The drainage field must be at least 10 metres from any watercourse, spring or borehole and at least 50 metres from any well or borehole used for drinking water. The ground must drain at a suitable rate, which is why a percolation test is carried out before design. The tank itself must be built to BS EN 12566-1 and installed to the manufacturer’s instructions.
No Pollution of Water
The discharge must not pollute surface water or groundwater. Within a Source Protection Zone 1, or close to a drinking water abstraction, tighter restrictions apply and a permit may be needed.
The Rules for Sewage Treatment Plants
A sewage treatment plant is subject to the same conditions on capacity and siting, with one important difference. Because the treated effluent is far cleaner, a plant that meets BS EN 12566-3, is correctly sized and is properly maintained can in most circumstances discharge to a surface water drain, ditch or watercourse without a permit. That is what makes a plant the practical answer on the clay sites and high water table plots we see so often in the Weald, where a drainage field is not an option.
What Happens If Your System Does Not Meet the Rules?
You have two routes. The first is to apply to the Environment Agency for an individual permit. That means an application form, a fee, and ongoing conditions on monitoring and reporting. Permits are reviewed and can be withdrawn if the conditions are not kept.
The second, and far more common, route is to bring the system into compliance. For a septic tank discharging to surface water that usually means either installing a drainage field, where the ground and space allow, or replacing the tank with a sewage treatment plant. As a 2026 guide, a replacement system installed on a typical domestic site falls somewhere between £8,000 and £18,000 depending on the plant, the ground and the access. We confirm the figure with a fixed-price quote after a site survey.
Maintenance Under the Rules
The rules do not set a fixed maintenance schedule, but they do require the system to be kept in good working order. In practice that means having a septic tank emptied by a licensed contractor at least once a year, keeping the drainage field free of compaction and waterlogging, having a treatment plant serviced annually by a qualified engineer, and keeping the paperwork. Records of servicing and emptying are increasingly requested when a property is sold.
Can You Sell a Property with a Non-Compliant System?
This is one of the questions we are asked most often. The short answer is that you can, but expect difficulty. The buyer’s solicitor will report on the drainage, a non-compliant system will show up, and buyers respond by negotiating the price down, making remediation a condition of the sale, or walking away. Putting the system right before the property goes on the market is nearly always the better commercial decision.
How Country Drainage Can Help
We survey and install Klargester septic tanks and sewage treatment plants across Surrey, Sussex and Kent, and have done for more than 40 years. We carry out the percolation test, assess the ground and advise on the most economical way to comply. Contact us for a free site survey and a fixed-price quotation.
Frequently Asked Questions
When did the ban on septic tanks discharging to surface water take effect?
The current General Binding Rules came into Force on 1 January 2020. Septic tanks discharging to surface water had to be replaced or upgraded by that date, or when the property was sold if that came first.
Do I need a permit for my septic tank?
Not if it discharges to a drainage field, serves 10 people or fewer and meets the other conditions. If it discharges to a surface water drain or watercourse you will need to change the system or apply for an individual permit.
What is a percolation test and do I need one?
A percolation test measures how quickly water drains through your soil. It tells us whether a drainage field will work at all and how large it needs to be. Every new septic tank or treatment plant installation needs one, and we carry it out as part of our free site survey.