Septic tanks and treatment plants: permits and general binding rules

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, for example from a toilet, bathroom, shower or kitchen of a house, flat or business (such as 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, for example in your back garden
  • to a surface water, for example 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 (such as a hotel, restaurant or office) or holiday accommodation (such as 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 (such as a hotel, restaurant or office) or holiday accommodation (such as 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 did not get permission and approval

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

You do not need to do this if your system was installed before 1 January 2015.