What Is a Soakaway?
A soakaway is an underground drainage system that collects rainwater from roofs, driveways, patios, and other hard surfaces, then gradually releases it into the surrounding soil. Rather than directing surface water into public sewers, it allows rainfall to soak naturally into the ground, helping to prevent flooding, reduce waterlogging, and support sustainable drainage.
Most modern soakaways consist of underground plastic soakaway crates wrapped in a permeable geotextile membrane, although older systems may be simple pits filled with gravel or rubble.
A soakaway is commonly connected to:
• Roof gutters and downpipes
• Driveway drainage systems
• Patio and paving drainage channels
• Surface water drains
• Land drainage systems
Unlike foul drainage systems, soakaways are designed to manage clean rainwater and surface water only.
Managing rainwater effectively is an essential part of protecting your property from flooding, waterlogging, and drainage problems. In this guide, we'll explain how soakaways work, their key components, where they're installed, common soakaway problems, and when to seek professional drainage assistance.
What Is a Garden Soakaway?
A garden soakaway is a soakaway installed within a residential garden to manage excess rainwater.
Garden soakaways are commonly used where:
• Lawns become waterlogged
• Rainwater collects around patios
• Downpipes discharge large amounts of water
• Surface flooding occurs after heavy rainfall
As they are buried underground, garden soakaways provide an effective drainage solution without affecting the appearance of outdoor spaces.
What Is a Soakaway Used For?
One of the most common questions homeowners ask is: What is a soakaway used for?
A soakaway is primarily used to:
• Manage rainwater runoff from roofs and hard surfaces
• Prevent standing water in gardens and outdoor spaces
• Reduce pressure on public drainage systems
• Lower the risk of flooding during heavy rainfall
• Improve overall drainage around a property
• Return water naturally to the ground
As rainfall events become more frequent and intense, soakaways play an increasingly important role in sustainable drainage and flood prevention.
How Do Soakaways Work?
Understanding how soakaways work is relatively straightforward when you break the process down into three stages.
Water Collection
The first stage involves collecting rainwater.
Water falling onto roofs, driveways, patios, and other impermeable surfaces is channelled through gutters, downpipes, drainage channels, orsurface water pipes.
Many systems include a silt trap or filter to prevent leaves, dirt, and debris from entering the soakaway chamber.
Temporary Storage
The collected water then flows into the soakaway itself.
Modern soakaways use specially designed plastic crates with a high void ratio, meaning most of the structure consists of space capable of storing large volumes of water.
During periods of heavy rainfall, the soakaway temporarily holds excess water and prevents it from overwhelming drainage systems.
Infiltration into the Ground
The final stage is infiltration.
The soakaway chamber is wrapped in a permeable geotextile membrane that allows water to pass through while preventing surrounding soil from entering and clogging the system.
Water gradually seeps out into the surrounding ground, where it naturally filters through the soil and recharges local groundwater supplies.
This controlled release is what makes soakaways such an effective and environmentally friendly drainage solution.
What Does a Soakaway Look Like?
Many homeowners wonder: What does a soakaway look like?
The answer is that most soakaways are completely hidden underground.
From the surface, there may be little or no visible evidence that a soakaway exists.
However, beneath the ground, a modern soakaway typically consists of:
• Plastic crate structures
• A geotextile membrane wrapping
• Drainage pipe connections
• A gravel or sand surround
• Inspection points where required
Traditional soakaways may simply be large pits filled with rubble, crushed stone, or gravel.
Key Components of a Soakaway Drainage System
A modern soakaway drainage system consists of several important components.
Soakaway Crates
Most new installations use modular plastic crates.
These lightweight structures provide excellent storage capacity while maintaining structural strength. Some systems offer up to 95% void space, allowing large amounts of water to be stored temporarily.
Geotextile Membrane
The crates are wrapped in a permeable geotextile fabric.
This allows water to escape while preventing soil particles from entering and blocking the system.
Inlet Pipework
Surface water is delivered to the soakaway through underground drainage pipes connected to gutters, channels, or drains.
Silt Traps and Filters
Many installations include pre-filters or silt traps.
These capture leaves, sediment, and debris before they reach the soakaway, helping to prolong the system's lifespan.
How Does a Septic Tank and Soakaway Work?
Homeowners with off-mains drainage systems often ask: how does a septic tank and soakaway work?
A septic tank and soakaway system works differently from a rainwater soakaway.
Wastewater first enters the septic tank, where solids settle and partially break down. The remaining liquid effluent then flows into a drainage field or soakaway system, where it filters naturally through the soil.
The surrounding ground provides further treatment before the water eventually returns to the environment.
These systems must be carefully designed and installed to comply with environmental regulations and ensure they operate effectively.
Where Should a Soakaway Be Installed?
The location of a soakaway is critical to its performance.
As a general rule, soakaways should be:
• Located at least 5 metres away from buildings
• Positioned away from foundations
• Installed above the water table
• Located in free-draining soil where possible
• Sized appropriately for expected rainfall volumes
Before installation, a percolation test is often carried out to determine how quickly water drains through the soil.
Soil types such as sand, chalk, and limestone tend to perform well, while heavy clay soils may not be suitable for soakaways.
Benefits of Installing a Soakaway
There are several advantages to installing a soakaway drainage system.
Reduces Flooding Risk
By storing and dispersing excess rainwater, soakaways help prevent localised flooding around properties.
Prevents Waterlogging
Soakaways reduce standing water in gardens, lawns, and landscaped areas.
Supports Sustainable Drainage
By returning water naturally to the ground, soakaways contribute to sustainable drainage practices.
Protects Property Foundations
Proper drainage helps prevent water from accumulating around buildings, reducing the risk of structural damage.
Reduces Pressure on Public Sewers
Diverting rainwater away from the sewer network can help reduce strain on local drainage infrastructure.
Common Soakaway Problems
Although soakaways are generally low maintenance, problems can occur over time.
Blockages
Leaves, silt, roots, and debris can restrict water flow into the system.
Soil Saturation
If the surrounding soil becomes compacted or naturally drains poorly, water may not infiltrate effectively.
Incorrect Sizing
An undersized soakaway may struggle to cope with heavy rainfall, leading to surface flooding.
Structural Damage
Older soakaways can collapse or become damaged due to ground movement or age.
Poor Installation
Incorrect placement or inadequate drainage design can significantly reduce performance.
Common warning signs include:
• Standing water around drains
• Waterlogged gardens
• Overflowing gullies
• Damp areas near the property
• Slow drainage after rainfall
When Should You Call a Drainage Professional?
If your soakaway isn't functioning correctly, professional assistance may be required.
Drainage specialists can investigate issues using CCTV surveys, drainage inspections, and infiltration testing to identify the root cause of the problem.
Whether you're experiencing drainage problems or planning a new soakaway installation, your local team can help ensure your drainage system operates effectively all year round.
Expert Soakaway Advice and Support from Drain Doctor
Soakaways are one of the most effective and sustainable ways to manage rainwater around a property. By collecting, storing, and slowly dispersing surface water into the ground, they help prevent flooding, reduce waterlogging, and protect buildings from water-related damage.
Whether you're looking to understand what a soakaway drain is, wondering how soakaways work, or experiencing problems with an existing drainage system, expert advice can make all the difference.
If you need help diagnosing drainage issues, inspecting an existing soakaway, or planning a new installation, contact our team at Drain Doctor for professional support and expert drainage solutions.