Who regulates septic tanks in Devon?
Devon is in England, so private sewage discharges are regulated by the Environment Agency. In England, small sewage discharges (up to 2 m³ a day to ground, or 5 m³ a day to surface water) don't need a permit if they meet the general binding rules. Under those rules, septic tanks must not discharge to surface water such as a ditch or stream, systems must meet the relevant British Standard and be sized correctly, and new discharges can't be in or within 50 metres of protected sites or in Source Protection Zone 1. Any new septic tank or treatment plant needs building regulations approval.
Building approval for a new or replacement system comes from your district council (East Devon, Mid Devon, North Devon, South Hams, Teignbridge, Torridge or West Devon), Plymouth, Torbay, or a registered building control approver. Read more in our England regulations guide.
Ground and soil conditions
North and mid Devon's Culm Measures produce heavy, wet clay soils, which often fail percolation tests. Dartmoor is granite with thin soils and peat. The red sandstone around Exeter and east Devon generally drains better. The variety means a site visit and percolation test are essential.
Protected waters and environmental checks
Devon has protected rivers and estuaries, including the River Axe Special Area of Conservation, where nutrient neutrality has affected planning, and the Exe estuary. It also has many bathing and shellfish waters. Septic tanks must not discharge to surface water in England, so properties with a stream outfall often need a treatment plant.
Local practicalities
Farmhouses, barn conversions and holiday lets are common across Devon, and steep lanes can make access hard for diggers and tankers. Dartmoor National Park Authority handles planning within the park.
Towns and villages covered
Installers we work with cover Devon, including:
- Okehampton
- Tavistock
- Crediton
- Tiverton
- Honiton
- Holsworthy
- Barnstaple
- Bideford
- Kingsbridge
- Totnes
- Ashburton
- South Molton
The list isn't exhaustive. Enter your postcode and we'll find installers who cover your property.
What it typically costs
The figures below are national guide prices from installers' published guides and merchants' list prices, because there's no reliable published data for Devon on its own. Expect your quote to reflect the local ground, access and discharge route described above.
- Like-for-like septic tank replacement: roughly £3,000–£7,000
- New septic tank with drainage field: from about £5,500; commonly £5,000–£15,000
- New drainage field: £3,000–£7,000
- Sewage treatment plant unit only: about £2,190–£2,700 inc VAT (equipment only)
- Sewage treatment plant, supplied and installed: commonly £7,500–£15,000
- Emptying: priced by volume. One private tanker firm charges £170 for up to 1,000 gallons and £380 for up to 4,000 gallons
Other areas in England
Norfolk · Suffolk · Lincolnshire · Cornwall · Cumbria · North Yorkshire · Northumberland · Shropshire · Herefordshire · Somerset · Dorset
Frequently asked questions
Our Devon septic tank goes to a stream. Do we have to change it?
Yes. In England, septic tanks discharging directly to a watercourse must be replaced or upgraded, usually with a small sewage treatment plant or by diverting the outlet to a drainage field. If you're selling, it has to be dealt with as part of the sale.
Is Culm clay suitable for a drainage field?
Often it isn't, without special design. A percolation test will tell you. Treatment plants with a suitable discharge, or engineered drainage fields, are common in north and mid Devon.
How much does septic tank replacement cost in Devon?
We don't publish made-up local prices. Installers' published guides put a like-for-like replacement at roughly £3,000–£7,000, a new tank with a drainage field at commonly £5,000–£15,000, and a treatment plant at commonly £7,500–£15,000 fitted. Ground and access in Devon can move your price either way, so compare site-visit quotes.