How to comply with the current septic tank rules (2020)

An owner of a septic tank which fails to meet new standards that came into force at the start of 2020 risks significant fines from the Environment Agency, and non-compliance may also make it more difficult to sell a property.

This article explains:

  • the problems and changes surrounding septic tanks
  • the new rules about septic tank systems
  • the options and responsibilities for affected homeowners
A new septic tank being installed.

What is the problem with septic tank systems?

Pollution incidents are rising, often due to poorly installed septic tank systems or lack of maintenance. A septic tank does not treat sewage in wastewater, it creates a soluble waste from solids, and the surrounding ground layers must filter this effluent before it reaches groundwater. If the filtration is inadequate, it can cause localised pollution. Sewage treatment plants are more effective as they break down the sewage and treat over 95% of pollutants before discharging effluence into a drainage field.

What are the changes?

To protect natural watercourses, it is not permitted to discharge from a septic tank system to a watercourse, or to any other type of soakaway system other than a drainage field. Owners of a septic tank system in England or Wales that discharges directly to surface water, such as a river, ditch or stream, are not compliant with the new legislation. The Environmental Permitting (England and Wales) (Amendment) (England) Regulations 2014 came into force on 1st January 2015 and created General Binding Rules for septic tanks or small sewage treatment plants for domestic use.

The rules mean that homeowners are responsible for ensuring their wastewater treatment systems operate correctly and do not cause pollution. The Rules are subject to review, and it is incumbent on homeowners to be aware of any changes. A septic tank not meeting the rules needed to be replaced by 1st January 2020; if this did not happen, swift action is needed otherwise the homeowner risks a fine.

The new septic tank regulations:

  • The discharge rate from a septic tank or sewage treatment system must be less than 2cu m/day.
  • The sewage must be treated by a septic tank and filtration system or a sewage treatment system.
  • The sewage must be domestic, i.e., coming from a bathroom, toilet, shower or kitchen of a house or business.
  • The existing discharge must not cause pollution to surface water or groundwater 5m from a boundary, 10m from a ditch or watercourse, 50m from a water abstraction point or 15m from any building and other soakaway network.
  • The discharge must not be within a groundwater source protection zone 1 or within 50m of a well or borehole used to supply domestic water.
  • Compliance with British Standard manufacturing standards is mandatory and septic tank systems must be correctly installed and maintained.

The options for septic tank owners:

1 Connect to a mains sewage system if possible.

2 Install a drainage field, also known as an infiltration system, designed to British Standard BS6297. This enables the septic tank to discharge into the ground..

3 Install a sewage treatment plant that meets BS EN 12566-3 standard to replace the septic tank.

4 In exceptional circumstances, a permit can be applied for to allow sewage discharge to surface water drains.

5 Septic tank conversion units can be used to upgrade an existing septic tank that discharges to surface water, but a permit is required along with specific evidence.

Operator’s Responsibility

General Binding Rules compliance is the responsibility of the operator of septic tank treatment systems. The operator may be the owner of the property where the treatment plant is located; the user (even if the system is located on a neighbour’s land), or the tenant/leaseholder.

Rules for new discharges from septic tank treatment plants installed on or after 1st January 2015.

If there was a discharge to surface water before 1st January 2015 and the aim is to change this to discharge to ground water (or the reverse), or if there was a discharge to ground before 1st January 2015 and the aim is to install a new drainage pipe to discharge more than 10m away from the existing one, this is the guidance:

  1. New discharge from a sewage treatment plant is not allowed if the building served by the treatment plant is within 30m of a public sewer.
  2. Apply for a permit if a public sewer is inaccessible; for instance, within 500m of a sensitive area such as an aquatic local nature reserve.
  3. Apply for planning consent and Building Regulations approval to install a new septic tank or sewage treatment plant.
  4. Seek Environment Agency advice regarding new discharges to ditches or surface water; this is only allowed if there is sufficient flow of water.


While rarely at the top of anyone’s list for property improvements, the septic tank regulations mean that non-compliant systems cannot be ignored. Protection of watercourses is paramount and substantial fines for causing pollution incidents are being handed out by the Environment Agency. Homeowners thinking of selling their property will also face problems if their septic tank system does not meet the new rules when it goes on the market. Finally, all sewage treatment plants must be checked to ensure that they:

○ Met the British Standard when installed or have a CE mark (not applicable to systems installed pre-1983).

○ Have the correct maximum capacity.

○ Meet the manufacturer’s installation requirements.

○ Undergo annual maintenance according to manufacturer specifications.

○ Are repaired or replaced if not working efficiently.

○ Meet regulations if sited in a tidal area where sewage release must be below the ‘mean low water spring mark.’

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