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Building over sewers

If your proposed development will be within 3 metres of a public sewer, including lateral drains, you will need to gain permission from South West Water

The Building Regulations list in priority the methods which can be used to carry foul water away from buildings.

Connection to a public sewer is the preferred option and must be used if a public sewer is located within 30 metres of your proposal unless there are factors (such as access being denied over private land) which prevent a connection being made.

Second priority is a connection to a private sewer.

If this is not practicable you can install either a septic tank and soakaway or another type of waste water treatment. These types of installation can require a considerable amount of land, where this is an issue the final option and fourth priority is the provision of a cesspool.

Further information and guidance can be found on the British Water website.

Septic tanks are normally purchased from builders merchants, however they can be constructed on site.

Before you install a septic tank you will need to determine that the land you have available is of sufficient size and that there are no other constraints such as wells, boreholes or other drainage fields within prescribed distances.

You must carry out a percolation test to determine the extent of soakaway required. It is essential that this exercise is carried out because it will determine the suitability of the subsoil as a drainage field and also how much area is required. The result of the percolation test may mean that a soakaway is not practicable and other options need to be explored.