If you own a property in Cornwall with a septic tank or small sewage treatment plant, the General Binding Rules 2020 apply to you. They replaced the patchier pre-2020 rules and set clear, nationwide requirements for how off-mains drainage systems must operate. This guide explains, in plain English, what you need to comply with — and what happens if you don't.

What are the General Binding Rules?

The General Binding Rules (GBR) are statutory rules issued by DEFRA and enforced by the Environment Agency covering small-scale sewage discharges. They came into effect on 1 January 2015 and were strengthened in 2020 with the well-known "no discharge directly to surface water from a septic tank" requirement.

If you have a septic tank, small treatment plant, or cesspit discharging less than 2 cubic metres per day (groundwater) or 5 cubic metres per day (surface water), you're covered by these rules — no separate permit usually needed.

The 8 core requirements (simplified)

The rules cover both what your system must do and how you must look after it:

  1. Capacity: Your system must be the right size for the property. Undersized systems must be replaced.
  2. Discharge type: Septic tanks must discharge to a drainage field, not directly to a watercourse, ditch, or stream.
  3. Treatment standards: Packaged sewage treatment plants must be CE-marked to BS EN 12566-3:2016 (the European standard for small wastewater treatment systems up to 50 population total). Septic tanks themselves are covered by BS EN 12566-1.
  4. Maintenance: Systems must be maintained "in good working order" — emptied regularly, repaired when needed.
  5. Records: Keep records of maintenance, emptying, and waste-carrier transfer notes.
  6. Location: Drainage fields must be sufficient distance from drinking water sources, buildings, and boundaries.
  7. Replacement on sale: If your system breaks the rules, you must fix it — including when you sell the property.
  8. No pollution: The system must not cause pollution of surface water or groundwater.

The big 2020 change: no direct discharge to watercourses

Before 2020, many older Cornwall septic tanks discharged effluent directly into streams, ditches, or rhynes. The 2020 amendment ended that practice. If your tank still discharges to a watercourse, you have two options:

  • Replace the septic tank with a sewage treatment plant that produces cleaner effluent (this can discharge to a watercourse with the right specification).
  • Install a drainage field so the septic tank discharges to soil instead.

The 2020 deadline was 1 January 2020 for already-known systems, but the Environment Agency takes a "fix on selling, repair, or failure" approach in practice. If you're staying put and your system is working, urgent replacement isn't always required — but you must fix it when you next have major work, or when the property is sold.

Are Cornwall properties commonly compliant?

Honestly? Many older Cornwall properties have grey areas. Rural Cornwall has a lot of historic systems installed before modern rules — concrete septic tanks discharging to ditches, soakaways under saturated land, missing drainage fields. The rule of thumb:

  • Pre-1990s property: Worth getting your system assessed if you're not certain it's compliant.
  • Discharge to a stream or ditch: Not compliant. Needs a drainage field or upgrade to a treatment plant.
  • System installed since 2000: Usually compliant if professionally fitted.
  • Buying a property: The compliance check is essential — see below.

Selling a Cornish property: GBR matters

When you sell, you must declare your sewage system honestly on the property information form (TA6) and confirm GBR compliance. If your system doesn't comply, the buyer or their solicitor will usually require you to fix it before completion (cost: £3,000–£15,000+).

This is one of the most common pre-completion holdups for Cornwall rural properties. A CCTV drain survey and assessment from a competent specialist is often the cheapest way to confirm compliance before listing.

Maintenance obligations

The rules don't specify exact emptying intervals, but require systems to be "in good working order." In practice:

  • Septic tanks: Empty when the manufacturer recommends (usually 6–12 months for domestic). See our full guide.
  • Treatment plants: Annual servicing by a competent engineer is standard.
  • Drainage fields: No specific intervention — but blocking or saturation needs investigation.

Keep records of every emptying and service. Waste transfer notes from licensed carriers are part of compliance evidence.

Penalties for non-compliance

The Environment Agency rarely prosecutes for unintentional non-compliance — their first step is usually a notice requiring you to fix the issue within a timeframe (typically 1–2 months for minor issues, longer for major work). Penalties escalate from:

  • Improvement / Enforcement Notice — fix it within a deadline, no fine
  • Variable Monetary Penalty (civil sanction) — since 11 December 2023 the previous £250,000 cap has been scrapped: the EA can now impose unlimited financial penalties, matching the maximum Crown Court fine. In practice, domestic septic-tank cases still land in the £1,000–£100,000 range; the unlimited ceiling is reserved for serious or repeat polluters.
  • Criminal prosecution — rare, reserved for deliberate pollution or refusal to comply

Most domestic property owners never see anything beyond a notice. But if pollution causes harm (e.g., contamination of a watercourse), enforcement gets serious quickly.

Practical compliance checklist

  1. Know what kind of system you have (septic tank, treatment plant, cesspit) and its capacity.
  2. Know where the discharge goes — drainage field, ditch, watercourse?
  3. Empty regularly and keep transfer notes.
  4. Service treatment plants annually.
  5. If your system discharges to a watercourse — get a quote for a drainage field or treatment plant upgrade.
  6. Before selling: get a current assessment, fix any issues.

If you're unsure where your system stands, submit your postcode and we'll match you with a Cornwall specialist who can do a proper assessment — typically £150–£250 — and tell you honestly what (if anything) needs doing to comply.

Further reading

The official rules are at gov.uk — General Binding Rules. For the related question of whether you need to register your system, see our guide: Do I need to register my septic tank?