This guide summarises the Environment Agency's guidance on gov.uk as checked in October 2026. Always read the official pages for your situation: discharges to the ground and discharges to surface water.
Septic tanks must not drain to a watercourse
A septic tank must discharge to a drainage field. If yours drains straight into a ditch, stream or river, the guidance says you must act as soon as possible: connect to the mains sewer, replace the tank with a small sewage treatment plant, or install a drainage field that meets the rules. Plans should usually be in place within 12 months.
Volume limits
To meet the rules, discharges to the ground must be 2 cubic metres (2,000 litres) a day or less, and discharges to surface water from a treatment plant 5 cubic metres (5,000 litres) a day or less. Above that, you need to connect to the sewer where reasonable or apply for a permit.
British Standards
Your system must meet the British Standard in force when it was installed. For new systems that means BS EN 12566 for tanks and treatment plants, and BS 6297:2007 for drainage fields. Systems installed before 1983 don't need to meet a standard but must still meet the other rules. Soakaways installed after December 2007 can't meet the rules.
Emptying and maintenance
The system must be maintained in line with the manufacturer's instructions and repaired or replaced if it isn't working properly, for example if it leaks, is blocked or smells. Sludge must be emptied at least once a year, or as the manufacturer says, by a registered waste carrier.
Building Regulations
You must have Building Regulations approval for a new septic tank or treatment plant, and you may also need planning permission.
Selling a property
When you sell, you must tell the new owner in writing that a sewage discharge is in place, with a description of the system, where the main parts and the discharge point are, any changes made, and maintenance details and records where available.
Do I need to register my septic tank?
In England there's no general registration for a septic tank or treatment plant that meets the general binding rules. If you need an environmental permit instead, it will appear on the Environment Agency's public register. Scotland and Northern Ireland have their own rules.
When you need a permit
You'll need an environmental permit if you can't meet one or more of the rules and can't connect to the sewer. Common triggers include being in a groundwater source protection zone 1, being within 50 metres of certain protected sites, or a public foul sewer being within 30 metres of your boundary.
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