You must follow the  opens in a new windowgeneral binding rules if you’re  opens in a new windowthe 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) –  opens in a new windowcontact the Environment Agency if you’re not sure if the sewage is domestic in nature
• not cause pollution – find out how to  opens in a new windowcheck 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

Releasing to the ground

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

You must  opens in a new windowapply 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  opens in a new windowcontact 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  opens in a new windowmap of protected zones – check whether your discharge is in the inner zone (Zone 1) or  opens in a new windowask 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  opens in a new windowapply 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  opens in a new windowcontact the Environment Agency for advice.

Installing a new system

You must have  opens in a new windowbuilding regulations approval. You may also need  opens in a new windowplanning permission.

Check with  opens in a new windowyour local council.

If you did not get permission and approval

You must apply retrospectively for  opens in a new windowplanning permission. You may also need  opens in a new windowbuilding regulations approval.

If your system was installed before 1 January 2015, you should contact your local council for advice.