Need Help?
Ask us on live chat
The Complete Guide To Soakaway Crates
What are soakaway crates?
Soakaway crates are modular underground drainage units designed to collect, store, and gradually disperse surface water back into the surrounding soil. They form an essential part of modern Sustainable Drainage Systems (SuDS), helping to reduce flooding and manage rainwater runoff from roofs, driveways, patios, car parks, and other hard surfaces.
Manufactured from durable recycled plastic, soakaway crates create a large underground void that can temporarily store significant volumes of water during periods of heavy rainfall. Once the rainfall subsides, the stored water slowly infiltrates into the surrounding ground.
Modern soakaway crate systems have largely replaced traditional rubble-filled soakaways due to their superior water storage capacity, easier installation, and longer lifespan. Quality soakaway crates typically offer a void ratio of around 95%, compared to approximately 30–35% for traditional stone-filled soakaways. This means they can store almost three times more water within the same excavation volume.
How Do Soakaway Crates Work?
A soakaway crate system works by capturing rainwater runoff and releasing it slowly into the ground.
The process typically follows four stages:
1. Water Collection
Rainwater is collected from:
-
Roof gutters and downpipes
-
Driveways
-
Patios
-
Car parks
2. Water Transportation
The collected water is carried through drainage pipes into the soakaway system.
3. Temporary Storage
The water enters the crate structure where it is stored during heavy rainfall events.
4. Ground Infiltration
The stored water gradually seeps through the surrounding geotextile membrane and into the natural ground, reducing pressure on local drainage networks and helping to prevent flooding.
Benefits of Soakaway Crates
Excellent Water Storage Capacity
One of the biggest advantages of soakaway crates is their high void ratio. Most systems provide approximately 95% usable storage space, allowing a relatively small excavation to store large volumes of water.
Reduced Flood Risk
By slowing the release of surface water into the ground, soakaway crates help minimise localised flooding and standing water around properties.
SuDS Compliance
Soakaway crate systems are a key component of Sustainable Drainage Systems (SuDS), helping developments comply with modern drainage requirements.
Space Efficient
Because of their high storage capacity, soakaway crates require smaller excavation areas than traditional soakaways.
Long Service Life
When correctly installed with geotextile membrane and suitable drainage components, soakaway systems can provide decades of reliable performance with minimal maintenance.
Easy Installation
Lightweight plastic crates are significantly easier to transport and install than large volumes of stone or hardcore.
Soakaway Crates vs Traditional Rubble Soakaways
Modern plastic soakaway crates have become the preferred solution for both domestic and commercial drainage projects due to their superior efficiency and storage performance.Soakaway Crates
- Approximately 95% storage capacity
- Smaller excavations required
- Lightweight and easy to install
- Consistent performance
- Long service life
Traditional rubble soakaways
- Around 30-35% storage capacity
- Larger excavations required
- Heavy materials to handle
- Can clog over time
- Less efficient use of space
What Size Soakaway Crate Do I Need?
The correct soakaway size depends on several factors:
- Roof area
- Driveway or paved area size
- Local rainfall levels
- Soil permeability
- Groundwater conditions
A small domestic property may only require a single cubic metre soakaway, while larger driveways or commercial projects may require multiple interconnected crates. For many domestic applications, a 1m³ soakaway system is often suitable for roof areas of around 50m², although proper calculations should always be carried out.
How Many Soakaway Crates Do I Need?
There is no universal answer because every site is different.
To calculate the number of crates required, you should consider:
- Surface area generating runoff
- Rainfall intensity
- Soil infiltration rate
- Crate storage volume
As a general guide:
Typical Soakaway Crate Requirements
- Garden shed or small roof: 1-2 crates
- Typical house roof: 4-8 crates
- Large driveway: 6-12+ crates
- Commercial developments: Site-specific design
How to Install a Soakaway Crate System
Step 1: Carry Out a Percolation Test
Before installing a soakaway, determine whether the soil can effectively absorb water. Clay soils often have poor drainage characteristics and may not be suitable.
Step 2: Select a Suitable Location
Building Regulations generally recommend positioning soakaways:
- At least 5 metres from buildings
- At least 2.5 metres from boundaries
- Away from underground services and utilities
Step 3: Excavate the Area
Excavate a hole large enough to accommodate:
- The crate system
- Geotextile membrane
- Surrounding backfill
Step 4: Install Geotextile Membrane
Line the excavation with a suitable permeable geotextile membrane to prevent soil ingress while allowing water infiltration.
Step 5: Assemble the Crates
Connect and stack the soakaway crates according to the manufacturer's installation guidance.
Step 6: Connect Drainage Pipes
Connect incoming drainage pipes from roofs, channels, or drainage systems.
Step 7: Wrap and Backfill
Wrap the completed system in geotextile membrane before carefully backfilling and reinstating the surface.
Building Regulations and SuDS Requirements
In the UK, surface water should be managed in accordance with Building Regulations and Sustainable Drainage System (SuDS) principles wherever possible.
Current guidance generally favours infiltration solutions such as soakaways before considering discharge into public sewers. Properly designed soakaway crate systems can help developments meet drainage requirements while reducing pressure on existing drainage infrastructure.
Common Applications for Soakaway Crates
Soakaway crates are suitable for a wide range of projects, including:
- Domestic roof drainage
- Garden drainage
- Driveways
- Patios
- Permeable paving systems
- Commercial developments
- Car parks
- Sports facilities
- Landscaping projects
Frequently Asked Questions
Do soakaway crates work in clay soil?
Clay soils drain very slowly and may not be suitable for standard soakaway systems. A percolation test should always be carried out before installation.
How long do soakaway crates last?
High-quality plastic soakaway crates can provide decades of reliable service when installed correctly.
Do soakaway crates need maintenance?
Maintenance requirements are generally low. However, drainage inlets, gullies, and pipework should be inspected periodically to prevent blockages.
Can soakaway crates be installed under driveways?
Yes. Many soakaway crate systems are specifically designed and load-rated for use beneath domestic driveways and commercial vehicle areas.
Can I install a soakaway without a percolation test?
You can, but it's not recommended. Installing a soakaway without testing the ground conditions can lead to standing water, flooding, oversizing costs, or drainage system failure. A simple percolation test provides valuable information that helps ensure your soakaway crate system performs effectively for years to come.
Are soakaway crates environmentally friendly?
Yes. They support Sustainable Drainage Systems (SuDS) by allowing rainwater to return naturally to the ground and reducing pressure on drainage networks.
Shop Soakaway Crate Systems
Whether you're managing roof runoff, installing a new driveway, or designing a larger drainage scheme, soakaway crate systems provide a modern, efficient, and cost-effective solution for surface water management.
Browse our range of soakaway crate systems to find the ideal solution for your project.