Septic tanks and treatment plants: permits and general binding rules

3. The general binding rules

You must follow the general binding rules if you’re the operator of a septic tank or small sewage treatment plant.


The sewage must:


  • be domestic in nature, eg from a toilet, bathroom, shower or kitchen of a house, flat or business (eg a pub, hotel or office) - contact the Environment Agency if you’re not sure if the sewage is domestic in nature
  • not cause pollution - find out how to check for pollution

There are other rules depending on whether you’re releasing this sewage:

  • to the ground, eg in your back garden
  • to a surface water, eg a river or stream

Ask your local installation or maintenance company if you’re not sure what sort of system you have.

Releasing to the ground 


You must use a septic tank or a small sewage treatment plant and a drainage field (infiltration system).


You must apply for a permit if you release (‘discharge’):


  • to a well, borehole or other deep structure 

  • more than 2 cubic metres (2,000 litres) per day 

  • in a groundwater source protection zone (SPZ1)

Calculate how much sewage you discharge


For sewage from a residential property, use the calculator to work out how much you discharge per day.



For commercial properties (eg a hotel, restaurant or office) or holiday accommodation (eg a cottage or chalet), use British Water’s flows and loads guidance or contact the Environment Agency for advice.


Work out if you’re in a groundwater source protection zone 1 (SPZ1)

An SPZ1 can be either:

  • the area around a commercial water supply shown on the map of protected zones - check whether your discharge is in the inner zone (Zone 1) or ask the Environment Agency
  • any area within 50 metres of a private water supply for human consumption - ask your neighbours if they have a spring, well or borehole, and how far it is from your drainage field


Releasing to a surface water


You must use a small sewage treatment plant. 

You must apply for a permit if you’re discharging more than 5 cubic metres (5,000 litres) per day. Use the calculator to work out how much you discharge per day.



For commercial properties (eg a hotel, restaurant or office) or holiday accommodation (eg a cottage or chalet), use British Water’s flows and loads guidance or contact the Environment Agency for advice.


Installing a new system

You must have both:

If you didn’t get permission and approval

You must apply retrospectively for both planning permission and building regulations approval.

You don’t need to do this if your system was installed before 1 January 2015.