2020 Changes to Septic Tank Operation – Updated

If your property does not drain to mains drainage, then a recent change to the regulations may affect you.
The General binding rules: small sewage discharge to a surface water determines which system you require to treat your waste, and new rules came into effect on the 1st January 2015.


Previous versions of the guidelines allowed the ‘treated’ water from a septic tank  to discharge to either:

  1. A drainage field so that the septic tank can discharge to ground or
  2. Directly to a watercourse – a river, stream, ditch, canal, or surface water drain

Under the new guidelines, option 2 is prohibited as from 1 January 2020.

If the septic tank was installed and in use before 31st December 2014, the installation is regarded as an ‘existing discharge’. If it came into use after 1 Jan 2015, then it is classed as a ‘new discharge’ and is subject the the new guidelines anyway.

So, if you have an existing septic tank discharging to surface water what options do you now have?

  1. Connect to a mains sewer if there is one available (if you have a septic tank, then this probably is not possible)
  2. Stop the discharge to the watercourse and install a drainage field that enables the septic tank to discharge to ground instead (The drainage field should be planned and constructed to BS 6297:2007+A1:2008 – Code of practice for the design and installation of drainage fields for use in wastewater treatment)
  3. Replace the septic tank with a small package treatment plant designed to BS EN 12566-3:2005. The treatment plant treats the waste liquid so that it should meet the required standard to enter a watercourse.

Action needs to be taken quickly to meet the deadlines – you will be in breach of the regulations if you do nothing.

As the 1st January 2020 deadline came and went the General Binding Rules were updated as follows:

If your septic tank discharges directly to a watercourse, you need to do one of the following as soon as possible:

  • connect to mains sewer
  • install a drainage field (also known as an infiltration system) so the septic tank can discharge to ground instead
  • replace your septic tank with a small sewage treatment plant

You must have plans in place to carry out this work within a reasonable timescale, typically 12 months.

There are, as would be expected, exceptions, restrictions and exemptions, but the Environment Agency are available to help and advise.

You have a new package sewage treatment plant. But how do I know it is performing as designed?