Common question, surprisingly simple answer: most domestic septic tanks in Cornwall do not need to be separately registered with the Environment Agency. As long as you comply with the General Binding Rules 2020, no formal registration is required. The big exception is tanks discharging to a watercourse — those need a permit. Here's the full picture.

The simple answer first

You probably don't need to register if:
  • Your septic tank discharges to a drainage field / soakaway (not directly to a stream or ditch)
  • You produce less than 2 cubic metres of sewage per day (basically any domestic household)
  • Your system was installed properly and complies with the General Binding Rules

You probably DO need to register / get a permit if:

  • Your discharge goes directly to a watercourse, stream, or ditch (even after the 2020 rule changes)
  • You're discharging more than 2 cubic metres per day to ground, or 5 cubic metres per day to surface water
  • You're running a commercial property, large holiday park, or anything beyond a typical home

Why the confusion?

Pre-2015, there was a more complex registration system run by the Environment Agency. Domestic property owners were supposed to register their septic tanks formally. Most never did, and the EA eventually accepted that the registration scheme wasn't workable.

The current system (General Binding Rules) replaced it: as long as you operate within the rules, no separate registration. If you don't comply, the EA can take action regardless of registration status.

When you actually do need a permit

Some Cornwall properties still need a formal Environment Agency permit. These cases are:

1. Direct discharge to a watercourse

If your treatment plant discharges effluent directly into a stream, ditch, or other watercourse, you need a permit. This is the most common case for Cornwall homeowners. The permit ensures the effluent meets specific quality standards before it enters the water.

How to apply: gov.uk — Septic tank permits. The standard application fee is £141.43 (2026 rate) for discharges up to 5,000 litres/day. The Environment Agency aims to decide within about 13 weeks. More complex cases requiring a bespoke "Permit to Discharge" can run up to £850.

2. High-volume discharges

If your sewage volume exceeds the thresholds (2 m³/day to ground, 5 m³/day to surface water), you need an environmental permit regardless of where it discharges. This typically affects:

  • Holiday parks with central treatment systems
  • Schools and community buildings with on-site treatment
  • Large agricultural operations
  • Commercial properties with on-site treatment plants

3. Discharges in protected zones

Properties in Source Protection Zones (areas around drinking water boreholes) or near Sites of Special Scientific Interest (SSSI) may need permits even at smaller volumes. Cornwall has several SPZs — check the DEFRA magic map for your area.

How to check what applies to you

  1. Find out where your system discharges. Most homeowners don't know — the answer is usually in the property survey or the original installer's documentation. If you can't find it, a CCTV survey can trace the outflow.
  2. Check what type of system you have. Septic tank, treatment plant, or cesspit? See our comparison guide.
  3. Check the daily volume. For domestic properties this is almost always under 2 m³/day (a 4-person household generates ~600 litres = 0.6 m³).
  4. Check your location. Source Protection Zone? Near an SSSI?
  5. If permit needed: Apply via gov.uk. The EA aims to decide within ~13 weeks; the standard application fee is £141.43 (2026) for discharges up to 5,000 L/day.

What if I've never registered and I should have?

For domestic systems, the EA's enforcement approach has historically been pragmatic. If you discover you need a permit, apply for one — they'll generally grant it without retrospective action provided your system is operating properly and not causing pollution.

If your system is causing pollution (e.g., visible contamination of a stream), enforcement is more serious. Get a competent specialist to assess and quote for any remediation before approaching the EA.

Cornwall-specific considerations

  • Coastal properties: Many older Cornwall coastal cottages have direct discharges to the sea via streams or ditches. These almost certainly need a permit.
  • Bodmin Moor / inland rural: Granite-based soils mean lots of properties have proper drainage fields. Usually no permit needed.
  • The Lizard / Penwith: High water tables in some areas force soakaway-impossible conditions, so direct watercourse discharges are more common. Check carefully.
  • Holiday lets: If treated as commercial (multiple lets, central system), the rules differ. Check whether your setup falls under domestic or commercial categories.

The bottom line

Most Cornwall homeowners with a typical septic tank discharging to a drainage field don't need to do anything formally — just operate the system properly and keep records. If you discharge to a watercourse, that's the trigger for a permit. If you're unsure where your discharge goes, that's the first thing to figure out.

Need an assessment of your Cornwall property's system? Submit your postcode and we'll match you with a licensed specialist who can survey and advise on what (if any) registration applies.