Soakaway Crates For Infiltration

Modern plastic soakaway crates are used for a number of purposes, namely rainwater recycling, attenuation and infiltration. In this article we take a brief look at infiltration.

What is Infiltration

Infiltration is the most common use for soakaway crates. It is the preferred method of managing stormwater in permeable soils, particularly when it is not suitable to discharge the rainwater further downstream or where there is no suitable natural outlet nearby. Essentially infiltration is a method of collecting stormwater from rainwater pipes in an underground void and allowing the water to seep back into the ground slowly over a period of time.

What are the benefits of infiltration?

Infiltration provides a natural recharge for groundwater aquafiers - underground boreholes and streams. The filtration process cleans the water, providing valuable fresh water for surrounding vegetation. Most importantly, soakaway systems reduce the strain on public stormwater drains and sewage treatment plants by reducing the demand on them. Some local authorities also offer a reduction in the water rates section of your sewerage bill if you have a soakaway installed - its always worth a check!

How does it work?

Rainwater pipes feed water into a localised surface water drain pipes. This runs to an excavation, usually sited in the garden and filled with soakaway crates that are wrapped in geotextile membrane. The crates themselves have a void ratio of 95%, meaning that 5% of this underground space is comprised of plastic and the other 95% is free to be filled with water. In our standard 1 cubic metre Ellipse soakaways this gives a water storage capacity of an eye-popping 934 litres!

The geotextile membrane around the crates prevents soil particles from entering the soakaway but allows a free flow of water.

Pre-filters installed prior to the soakaway add an additional level of cleaning by taking sediment out of the water. This improves water quality and increases the life of the soakaway.

Are all sites suitable for infiltration by soakaways?

Provided your soil is permeable, you don't have a very high water table (the level at which water is naturally found in the soil), and your chosen site is not within 5m of yours or any other property (for domestic soakaways) your site should be suitable.

Very heavy clay soils are not suitable as the clay holds the water in suspension rather than allowing it to infiltrate down through the soil layers. If your soil is not fully clay but is heavier than normal you should consider our soakaways for heavier soils.

If you are unsure as to whether your soil is suitable for a soakaway, check first with your local planning officer. You can also carry out a soil percolation test which will help determine the rate of infiltration for your soil.

Is it easy to install a soakaway?

Yes, installation is a relatively simple process - definitely easier if you hire a mini-digger! For full instructions on how to go about the installation we suggest reading our article Building Your Soakaway.