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Soakaway Installation & Repair in Derby

A soakaway disperses surface water and roof run-off into the ground. When it fails or underperforms — waterlogged garden, overflowing gullies in heavy rain — we assess your ground conditions, design a correctly sized replacement, and install to current regulations.

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What a Soakaway Does

A soakaway is an underground drainage structure that collects surface water — from roofs, drives, or patios — and allows it to percolate gradually into the surrounding soil. It is the standard method for managing surface water on properties that cannot discharge to a surface water sewer or watercourse.

When a soakaway is working correctly, surface water drains away quickly after rain and the garden or drive does not flood. When it fails, the first signs are usually standing water after heavy rain, an overflowing gully or downpipe, or a persistently waterlogged area of garden above where the soakaway is buried.

Why Soakaways Fail in Derby

Derby and Derbyshire sit on predominantly clay-heavy subsoil, particularly in areas like Chellaston, Mickleover, Littleover, and the Trent Valley. Clay has low permeability compared to sandy or loamy soils — water passes through it slowly, which means a soakaway must be correctly sized to compensate. Many soakaways installed in Derbyshire were sized for more permeable conditions and simply cannot cope with the actual infiltration rate.

Beyond soil type, soakaways fail for several other reasons:

  • Silting: Fine particles wash into the soakaway over years and gradually fill the voids, reducing storage capacity and percolation rate. A rubble-filled soakaway silts more quickly than a plastic crate system.
  • Undersizing: The original installation did not account for the full roof or surface area it would serve, or additional hard surfacing was added later (a new extension, a paved drive) without upgrading the soakaway.
  • Age: Traditional rubble soakaways from the 1970s and earlier are frequently at the end of their effective life. The rubble has compacted and the drainage capacity is gone.
  • Root damage: Tree roots from nearby trees can penetrate and displace soakaway structures.

Our Process — Percolation Test First

  1. Site assessment: We identify the area to be drained, the existing soakaway location (if replacing), and the soil type.
  2. Percolation test: We excavate a test pit and measure the actual infiltration rate of the soil at the depth where the new soakaway will sit. This determines the required soakaway volume to current BRE Digest 365 standards.
  3. Design and quote: Based on the test result and the area to be drained, we design a correctly sized soakaway and give you a fixed price.
  4. Installation: We excavate, install a geotextile-wrapped plastic crate system (or alternative), connect the incoming drainage, and backfill correctly.
  5. Test: We run water through the complete system to confirm it is performing correctly before leaving.

When a Soakaway Is Not the Answer

If the percolation test shows the soil has very low permeability — as is sometimes the case in heavy clay areas — a conventional soakaway may not be able to discharge water fast enough regardless of size. In these situations, alternative options include a French drain discharging to a watercourse (where one is accessible), connection to the surface water sewer (where permitted), or a flow attenuation system. We will explain all options honestly after the percolation test.

Related services: Drainage Repairs · Blocked Outside Drain · Domestic Drainage

Areas We Cover

Not sure if we cover your area? Call us — we serve all of Derby and surrounding Derbyshire.

Frequently Asked Questions

Why does my garden flood in heavy rain even though there is a soakaway?
Three things typically cause this: the soakaway has silted up and lost its percolation capacity, it was undersized for the roof or surface area it serves, or the surrounding soil — particularly clay — has a lower percolation rate than was assumed when it was installed. A failed soakaway cannot be repaired by jetting; it usually needs to be replaced and resized. We assess the ground and size the replacement correctly.
Do I need building regulations approval for a soakaway?
For a new soakaway serving surface water drainage from a new building or extension, building regulations approval is required. Replacing a failed soakaway like-for-like under permitted development rules is generally permissible without full approval, but we advise checking with your local authority. We design installations to current BS EN 752 / BRE Digest 365 standards and can provide documentation for building control if required.
How long does a soakaway last?
A soakaway installed to modern standards with a plastic crate system will last 30–50 years under normal conditions. Traditional rubble-filled soakaways have a shorter effective life because the voids fill with silt over time. If your soakaway is more than 15–20 years old and is struggling, it is likely nearing the end of its useful life rather than experiencing a fixable fault.
Will a soakaway work in Derby's clay soil?
It depends on the depth and precise soil profile at your location. Clay-heavy subsoil has low permeability, which limits how fast the soakaway can discharge water. We conduct a percolation test to measure the actual infiltration rate at the installation depth before designing the system. In some locations, an oversized crate soakaway will work; in others, an alternative drainage solution — a French drain discharging to a watercourse or the surface water sewer — may be more appropriate. We will tell you honestly which applies.

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