Do you need planning permission for a septic tank?

Septic tanks are used to safely dispose of wastewater in homes
Septic tanks are used to safely dispose of wastewater in homes (Image credit: Getty Images)

Household draining legislation can be complicated and generates a lot of confusion, but do you need planning permission for a septic tank?

A septic tank is an underwater sedimentation tank that treats wastewater from household plumbing produced by bathrooms, kitchen drains, and laundry through biological decomposition and drainage.  

Simply put, a septic tank system is an underground watertight container made of fibre glass, plastic or concrete and is usually rectangular or round.

They are used to safely dispose of wastewater in homes that have poor drainage or are not connected to the mains sewage network, such as those in rural areas.

Whether you are upgrading or replacing an existing septic tank, installing a new one, or moving it, there are a number of aspects you must be aware of.

Homebuilding and Renovating spoke to HomeHow.co.uk property construction expert Natalie Mitchell about the regulatory challenges presented by some drainage systems.

Do you need planning permission for a septic tank?

If you are adding an off-mains drainage system such as a septic tank to your property you are likely to need planning permission, but you should confirm this with your local authority as it may not always be the case.

Paragraph 20 of the government's Planning Practice Guidance, which all local authorities should abide by, states that "applications for developments relying on anything other than connection to a public sewage treatment plant should be supported by sufficient information to understand the potential implications for the water environment".

Natalie from HomeHow.co.uk points out: “It’s your responsibility, rather than your water company’s, to make sure your sewage isn’t polluting local rivers and lakes and meets current regulations. This means getting the drainage design right and securing the relevant consents, permits and registrations.

“Just to complicate matters, this varies between England, Scotland, Wales and Northern Ireland – but not doing so can land you with an eye-watering fine.”

She adds: "Ideally, you want to work with specialist installers to help you with the planning and design to make sure you don’t skip any important steps.”

You can also read our guide on what is a septic tank for more detail on this type of drainage system.

How far does a septic tank need to be from a boundary?

In the UK, a septic tank needs to be located five metres from a boundary, but there are other considerations. It also needs to be five metres from any trees and hedges, regardless of where your property boundary is.

Natalie adds: “You should also make sure it’s at least four metres away from walls and buildings.

“Some of the other positioning rules, such as the minimum distance from your house, differ depending on where you live in the UK.”

Do septic tanks need building regulations?

All septic tanks and sewage treatment plants need building regulations approval. Your model of tank also needs to meet the current British Standards when it’s installed. You can read more about the building regulation requirements for septic tanks in the Building Regulations Approved Document H on drainage and waste disposal requirements.

Septic tanks are not the only option for an off mains drainage system. Check out our guide on each off mains drainage system for information on other options.

Do septic tanks need any other permissions?

Not only are new septic tank installations likely to need planning permission and building regulation approval but they are also likely to need a permit from the Environment Agency as well as filling in a Foul Drainage Assessment form.

The government's planning portal explains: "Any discharge from a wastewater treatment system is likely to require a permit from the Environment Agency. Those seeking Building Regulations approval for non-mains drainage should contact the area office of the Environment Agency in order to determine whether a permit to discharge is required and what parameters apply."

And it is prudent to contact the Environment Agency about your planned septic tank installation before submitting a planning application or applying for building regulations approval. This is because the Environment Agency permit can have a direct bearing on what type of system can be installed.

Natalie from HomeHow.co.uk adds that it’s easy to read the rules and misinterpret them and you may also have extra permissions to secure depending on where you live. For example, you may need extra consent from the Environment Agency, SEPA or DAERA. Reasons for this include living near a chalk river, protected wetland or pearl mussel water.

“You also need to make sure your septic tank or sewage treatment plant has the correct capacity to deal with your sewage, which can be hard to calculate,” Natalie explains. “Checks also need carrying out to see if your system can be connected to the mains sewer."

Are septic tanks now illegal?

Septic tanks aren’t illegal, but the rules have been tightened to stop sewage leaching into watercourses.

Since 2015 you are no longer allowed to discharge from a septic tank to a watercourse, or to any other type of soakaway system other than a drainage field. This has given rise to the false belief that they are illegal, combined with the fact that cesspits are illegal in Scotland because of environmental concerns from leakage, but are allowed in England and Wales.

Septic tanks and cesspits are not the same. A cesspit is simply a single-chamber holding tank for wastewater and does not treat or breakdown the sewage it collects.

The main difference between a cesspit and a septic tank is that a cesspit has no outlet pipe while a septic tank does. For more information, check out our expert guide on what is a cesspit.

Sam Webb

Sam is based in Coventry and has been a news reporter for nearly 20 years. His work has featured in the Mirror, The Sun, MailOnline, the Independent, and news outlets throughout the world.  As a copywriter, he has written for clients as diverse as Saint-Gobain, Michelin, Halfords Autocentre, Great British Heating, and Irwin Industrial Tools. During the pandemic, he converted a van into a mini-camper and is currently planning to convert his shed into an office and Star Wars shrine.