Rainwater drainage: what is a soakaway?

Soakaways are a useful addition to your property’s rainwater drainage. Mark Brinkley explains how they work and how you can build your own…

- Mark Brinkley

Soakaways are a long-established way of dealing with rainfall. They are essentially a pit in the ground into which you run your rainwater drainage. They are also used, less frequently, to dispose of the effluent from septic tanks, where they are more commonly known as leach fields. The overall idea is much the same — it’s a way of disposing of surplus water slowly, by directing it away from the house or hardstanding and letting it seep into the ground. This both mitigates against flooding and stops damage to the house and its foundations.

Solutions for surface water runoff aren't optional either — it’s covered by Part H of the Building Regulations for new homes.

GETTING STARTED

First ensure the ground beneath is permeable, which will need a percolation test. A soakaway has to let the water soak away if it is to be successful.

To do a percolation test, dig a hole in your garden measuring about 300mm square and 300mm deep. Pour at least 10 litres of water into that hole. If the water has soaked away within about two hours then soakaways should work very well.

However, if the water sits in the hole without draining, then you will have to explore further. First consider a deeper percolation test, going down to a depth of a metre. If the water still stands without draining away, then you will have to seek an alternative destination for your rainwater drainage.

Instructions for doing a more accurate soil percolation test, as well as for installing soakaway crates, can be found at www. drainage pipe. co.uk