Digging a soakaway for a septic tank

The first thing to remember when digging a soakaway is that there are two distinct types. The first is for surface water, which allows it to soak away and prevent flooding. The second type of soakaway is for a septic tank and serves a very different purpose, albeit using the same principles.

It is also worth remembering that a septic tank soakaway has two functions. The first is to soak away the septic tank liquid to prevent it overflowing. The second is to further treat the effluent liquid and remove suspended solids, as well as bacteria and viruses. Only when this has happened is the liquid safe to be soaked away into the soil. If the soakaway is not correctly constructed, it can contaminate the drinking water and groundwater in the soil.

Sizing your soakaway

The first thing to consider is the size of the soakaway, which is dependent on the size of the septic tank and the amount of use you expect it to get. This can be determined by the number of bedrooms or expected users the soakaway is going to be used by. You also need to factor in the porosity of the soil, so you may need to conduct a soil sample test before construction starts.

Position of your soakaway

Your soakaway site should be positioned at least ten metres from a watercourse or ditch, and at least 50 metres from any water abstraction points. It should be 15 metres from any building or other soakaway site and positioned downslope of any groundwater source. The bedrock must not be within a metre of the bottom of the soakaway.

Construction

Sewage soakaways are designed using a series of trenches and pipes, laid in gravel beds. These are covered with other stones and membranes before a final layer of topsoil is backfilled on the top. You need to use the correct materials, designed and recommended for use as part of a soakaway. You will also need to carry out percolation tests to make sure your soakaway is working correctly. Ideally, you need a professional team of groundworks contractors, like us here at APEC, to ensure that your soakaway is sited, sized and constructed in a professional and legal way.

Get in touch with our team on 01379 673 024 to find out more.