A vital part of any septic tank is its soakaway or drainage field, without this a septic tank may not be the correct option. (Sewage treatment plant or a cesspool)

Building Regulation state, soakaways should be sited so as not to have an adverse effect on the sub structure of any buildings

Apart from the Building Regulations there are various good practices regarding the positioning of a soakaway;

•    Avoid sitting within 5 metres of a road or highway.
•    Avoid sitting within 2.5 metres of a boundary.
•    Note that areas with a high water table are likely to be unsuitable.
•    Any new soakaway should not compromise existing systems.


Permeable sub-soils such as sand, along with permeable bedrock types, such as limestone, sandstone or chalk, are usually good areas to have a soakaways.

Whereas hard, igneous rocks, such as granites and basalts, and heavy soils such as clay may mean a soakaway is not going to be feasible.

There are many different type of soakaways available for septic tanks, the most common being a herringbone system.

Septic Tank Supplies are able to supply both 110mm sewage pipe and 110mm perforated pipe used in the installation of soakaways.

Design and Construction of your Soakaway

Soakaways should be always constructed with perforated pipe, and laid in trenches with the same gradient not steeper than 1:200

Pipes should be laid on a 300mm layer of shingle or medium of up to 50mm.

The trenches must be filled 50mm above perforated pipe and covered with a membrane and then filled in with soil.

The trenches for a soakaway should be between 300mm and 900mm wide with a distance of 2m between trenches.

It is recommended that an inspection chamber should be installed between the septic tank and the soakaway. (this is to make sure no solids are coming out through the outlet pipe into your soakaway)

Other Factors

Drainage fields are not to be constructed under driveways, parking areas, buildings, near

trees, dwellings, boundaries, watercourses & boreholes.







 The minimum size of a soakaway should not fall below 30m

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