A bre 360 soakaway is a vital part of sustainable drainage systems where surface water needs to be managed. Used in the UK, soakaways allow surface water to infiltrate into the ground rather than overwhelming the local drainage system. This article will cover everything you need to know about soakaway testing, what it is, why it’s necessary, how it’s done and some tips.
What is a Soakaway?
A soakaway is a hole filled with gravel or similar material where rainwater can percolate into the ground. This is especially useful in flood prone areas or where the main drainage system can’t cope with excess water. Soakaways are used for managing rainwater runoff from roofs, driveways or other hard surfaces.
They can be simple, a hole filled with rubble or specially designed plastic crates to store and slowly release water into the surrounding soil.
Why is Soakaway Testing Necessary?
Before you install a soakaway you need to know if the soil in your area can absorb water. Soil types vary across the country and not all soils are suitable for soakaways. For example clay soils have poor drainage and sandy soils are better at absorbing water.
Soakaway testing, also known as a percolation test, measures how quickly water drains away in a specific area. The results of this test will inform the design and construction of the soakaway so it works correctly and doesn’t waterlog or flood.
Testing is necessary for:
- Regulatory Compliance: In many areas planning authorities require percolation tests to ensure soakaways won’t create water runoff problems.
- Environmental Protection: Good soakaway systems protect local watercourses from contamination by managing surface water on site.
- Flood Prevention: Properly tested and designed soakaways reduce the risk of flooding on your property.
The Soakaway Test Process
Soakaway testing is usually done by professionals but understanding the process will help you make informed decisions when planning your project. The standard test involves digging a trial pit and then monitoring how quickly water disperses.
Soakaway Testing Step by Step
- Selecting the Site:
- Choose a site where the soakaway will be installed.
- The test location should be away from buildings, boundaries and underground utilities.
Excavating the Test Pit:
- Dig a test pit 300mm x 300mm in area and at least 1 meter deep.
- For larger soakaways deeper pits may be necessary.
- Make sure the sides of the pit are vertical to mimic the conditions of the actual soakaway.
Saturating the Soil:
- Before the test fill the pit with water and let it drain away naturally.
- This pre-soak ensures the soil reaches its natural absorption rate and prevents over optimistic results.
Filling the Pit for the Test:
- After pre-soaking fill the pit with water to a depth of approximately 300mm.
- Measure how long it takes for the water to drain away using a stopwatch.
Calculating the Percolation Rate:
- The percolation rate is calculated by dividing the time taken for the water to drop by the depth of water.
- Repeat this process several times to get an accurate average percolation rate.
Interpreting Results:
- If the water drains too quickly the soil may be too permeable and the soakaway won’t work.
- If the water drains too slowly the soil may not be suitable for a soakaway and alternative drainage solutions should be considered.
Soakaway Testing Regulations
In the UK there are specific regulations for installing soakaways particularly in relation to the Building Regulations and Sustainable Urban Drainage Systems (SuDS). To comply with these regulations soakaway testing must be done in a specific way. This ensures the results are reliable and the soakaway will work over time.
According to the Building Regulations a soakaway must be at least 5 meters away from any buildings so water doesn’t affect the foundations. Also the system must be able to handle a 1-in-10 year storm event without overflowing.
SuDS which aim to manage surface water in an environmentally friendly way often require soakaway testing as part of a wider assessment. The goal is to minimize the impact of new developments on local water systems and reduce the risk of flooding.
Soakaway Testing Pitfalls
Soakaway testing is relatively straightforward but there are several pitfalls:
- Inaccurate Test Pit Depth: Making sure the test pit is the correct depth is crucial for accurate results. Too shallow or too deep can give misleading results.
- Inconsistent Results: Recent rainfall or an unusually dry period can skew results. The test should be done in typical weather conditions for the area.
- Misinterpreting Soil Saturation: If the soil isn’t properly saturated before testing the absorption rate will be overestimated and the soakaway will perform poorly.
- Choosing the Wrong Soil Type: Not all soils are suitable for soakaways. If the soil is too impermeable you may need to look into alternative drainage solutions such as a rainwater harvesting system or connecting to the main drainage network.
Top Tips for Soakaway Testing
- Hire a Professional: You can do soakaway testing yourself but it’s recommended you hire a professional. They will have the equipment and knowledge to interpret the results correctly and to comply with regulations.
- Choose the Right Time of Year: Do your soakaway test during typical weather conditions. Avoid testing during extreme weather like prolonged drought or heavy rain as this can skew the results.
- Consider Soil Variability: If your site has different soil types consider doing multiple tests in different locations to get a full understanding of how the soakaway will work.
Other Options
If your soil isn’t suitable for a traditional soakaway there are other drainage solutions:
- Rainwater Harvesting: Collect and reuse rainwater for irrigation or other non-potable uses to reduce the demand on the drainage system.
- Swales: Shallow, vegetated channels that slow and direct the flow of surface water so it can filter into the ground naturally.
- Attenuation Tanks: Underground tanks that store excess water and release it slowly to reduce flooding.
Soakaway testing is a key part of managing surface water on your site. By understanding the process and working with professionals you can get your soakaway working effectively and protect your home from flooding and contribute to a sustainable drainage system.
Whether you’re building new or upgrading an existing property a soakaway system is a practical and environmentally friendly way to manage water runoff. But testing is crucial to make sure it will work as intended and make your investment worthwhile in the long run.
