The installation of a soakaway is not an exact science but there are formulas to assist in obtaining the correct design. It cannot be exact due to the fluctuation of the volumes of water whether foul or storm.
PERCOLATION TESTS tell us how long it will take on average for a certain volume of water to disperse into the soil. There are various designs ranging from perforated pipe to soakaway crates, and the results provide the basis for calculating not only the design, but also the size and location of the proposed soakaway.


Rain/surface water soakaways generally require holding capacity because there is often a large volume of water delivered to the soakaway in a short period of time. When this occurs the volume of water is greater than the sub-soil can disperse over the same period of time.
The design should provide a storage facility so the water can be collected quickly and stored, then dispersed as the soil will allow. However, soakaways are not always the answer and will not always cope during prolonged or heavy rainfall.