What is a soakaway? Why would I use one?

By Jonathon McAllister

How soakaway systems manage rainwater, prevent flooding, and keep your outdoor spaces dry

A soakaway is a simple underground system that lets excess rainwater soak into the ground rather than pool or flood. It fits well with Raincatcher’s practical, solutions-focused tone.

Section 1: What’s a soakaway?

Underground pit or crate system
Surface water is diverted underground
Water disperses into soil over time, stopping waterlogging and pooling

Section 2: Why bother?

Part of SuDS (sustainable drainage systems) to manage runoff from new builds or paved areas
Helps prevent localised flooding, reduces pressure on sewers
Mimics natural water movement into soil — efficient, cost-effective, low-maintenance

Section 3: Soakaway methods – old vs new

Traditional: hole filled with rubble or hardcore. Short-term fix; blocks easily, unpredictable capacity, potential contamination, and no structural strength.
Modern: plastic crate systems:
- High void ratio with known storage capacity
- Uniform shape, easy to stack and connect
- Wrapped in geotextile to block debris and soil
- Strength tested for garden and driveway use
- Made from virgin materials for long-term durability

Modern crates provide a reliable, engineered solution that meets drainage regulations and avoids the common failures of rubble soakaways.

Section 4: Practical example

John added a single-storey extension, increasing impermeable surfaces. He saw pooling on his patio and soggy garden during heavy rain.

A soakaway solves this by:

Removing surface water quickly
Redirecting water underground gradually

Before installation:

Percolation test for soil drainage
Calculate needed water capacity using impermeable area (m²)
Position soakaway away from buildings/boundaries
Check local council rules or permits

Section 5: Choosing and installing crates

Crate sizes: 100 L, 190 L, 300 L, 400 L. Stackable and linked with connectors
Wrap in non-woven geotextile
Bed in clean pea gravel for better water flow
Use perforated pipe with correct fall to feed water in

Extra tips:

Consider load rating — driveways need stronger crates (e.g., 60-tonne)
Add a silt trap at the inlet to catch debris before it reaches the crates

Section 6: Maintenance and regulations

Maintenance is low, but check inlets and silt traps yearly to clear leaves, grit or moss.
Keep nearby drains and gutters clear to prevent blockages.
Avoid planting large trees close to the soakaway to reduce the risk of root intrusion.
Plastic crates last far longer than rubble pits, giving consistent performance.

These checks keep your soakaway working efficiently and compliant with building standards.

Section 7: Summary checklist

Step	Task
1	Run percolation test
2	Measure area; estimate crate volume
3	Pick crate size/load rating
4	Choose site (distance, access)
5	Excavate, lay gravel, crate, membrane, pipe
6	Add silt trap
7	Backfill, reconnect drains, mow or pave
8	Maintain and check periodically

Closing thoughts

Soakaway systems are Raincatcher-worthy. They’re simple, effective, regulatory-friendly, and help avoid soggy gardens or patios. Choose the right crates, site it well, keep it clean – enjoy dry ground from now on.