What are Soakaways?

by | Sep 20, 2022

When living in the UK, there is one thing for certain – rainfall. More often than not, river-adjacent towns or cities have seen the occasional washout or flood. This leads to the question, “What are soakaways? Do I need one?”. If the threat of flooding is consistent for a commercial or private facility, then action must be taken! This is when a soakaway installation should be considered.

Our team at Borehole Solutions, an industry-leading geotechnical drilling company in the UK, would like to offer more insight into the humble soakaway, including what they are and when they are required.

What is a Soakaway?

In the simplest of terms, they are a form of drainage. Soakaways consist of a storage device, filled with either concrete rubble or flint, which filters the excess water in a controlled manner. This drastically reduces the chances of surface runoff water escalating into a flood. Some form of guttering is used to transfer the runoff water into the soakaway.

They are extremely cost-effective and also work in almost every situation. Recently, newly designed soakaway crates, as opposed to the concrete rubble, have proven to work efficiently. These features also have the additional benefit of replenishing the groundwater, meaning they help with ecological processes!

When should I install a Soakaway?

Soakaways can be installed in both rural areas, where a lack of storm drains results in a higher risk of flooding, as well as urban environments. They are often found in gardens of suburban homes, especially those that regularly become waterlogged. Consequently, the majority of urban planning approvals now require a check for soakaway suitability.

Another advantage of installing a soakaway is the fact that it is an invisible feature, meaning it will not be an eyesore for either you or the community. With this in mind, there are very few reasons not to have a soakaway installed in a rain-prone area.

Checks and Tests 

Unfortunately, you can’t simply go ahead and install a soakaway without performing the necessary checks and tests beforehand. Percolation tests (also known as perc tests) help to determine whether the ground conditions are suitable for the installation of a soakaway. This test finds the rate at which the soil can absorb water. One of the testing standards is called the BRE Digest 365.

BRE Digest 365 

To meet these standards, soakaways must show that the water stored drains away quickly enough so that it can provide the necessary support for subsequent rainfall. According to the Building Research Establishment (BRE), the feature should discharge 50% of the water volume, for example from 75% full to 25% full.

To meet the BRE standards, the following test is carried out:

  • Firstly, a trial pit is excavated. This can be dug by hand or with the use of mini-diggers, and it is used to replicate the intended soakaway.
  • The pit is then filled with water repeatedly in a short amount of time. Whilst this is being carried out, the rate of percolation is measured.
  • The calculations are used to determine the size of the soakaway required. 

Sustainable Drainage Systems (SuDS)

When planning the installation of a soakaway, the following must be considered:

  • Water quantity.
  • Water quality.
  • Biodiversity.
  • Amenity.

Collectively, the above are referred to as Sustainable Drainage Systems (SuDS). These are designed to transport surface water, slow the run-off, and they can allow water to infiltrate into the ground or be evaporated from surface water or lost from vegetation. SuDS are considered to be beneficial for the environment, causing minimal long-term issues. They are often regarded as management practices and control strategies that are designed to efficiently drain surface water, whilst minimising pollution and managing the impact on local water quality. 

Contact Borehole Solutions 

We offer comprehensive percolation testing, as well as soakaway installation, along with numerous other geotechnical services. If you’d like to find out more about our BRE365 testing or any other drilling solution, then get in touch today! Contact us on 01733 200501 or email us at info@boreholesolutions.com.