Soakaway and Land Drainage Installation in North Devon: How Surface Water Is Dealt With Properly
Every roof, patio and driveway collects rainwater, and that water has to go somewhere. On a flat site with free draining soil, it may soak in without help. In Ilfracombe, where gardens climb steep hillsides, soil can be thin over rock, and winter rain arrives sideways from the Bristol Channel, water needs a plan. A soakaway or land drain is often the answer. This guide explains how a soakaway works, how drains are designed, when each is suitable, and what goes wrong when they are installed badly.
Crabb Contractors Ltd has been laying drains, digging soakaways and shaping ground in Ilfracombe since 1962. We have seen waterlogged lawns, damp walls and flooded drives that all trace back to the same cause: nowhere for the water to go.
Quick Answer: What Is a Soakaway?
Short answer: A soakaway is an underground pit or chamber that collects rainwater from roofs and hard surfaces and lets it drain slowly into the surrounding soil. It works only where the ground can absorb water, which is checked with a percolation test, and it must be sited a safe distance from buildings and boundaries.
A land drain, sometimes called a French drain, is a different tool. It is a perforated pipe in a gravel filled trench that collects groundwater or surface water and carries it away to a suitable outlet.
Soakaway or land drain: which does what?
Feature | Soakaway | Land drain (French drain) |
Main job | Gets rid of rainwater from roofs and paving | Lowers wet ground and intercepts water |
Water source | Downpipes, channel drains, paved areas | Soggy lawns, springs, runoff from slopes |
Where water ends up | Soaks into surrounding ground | Carried to a ditch, soakaway or approved outlet |
Needs permeable ground | Yes | Not always, as it carries water elsewhere |
Typical form | Crate chamber or stone filled pit | Perforated pipe in a gravel trench |
Why Drainage Matters So Much in North Devon
North Devon is wetter than much of England. Hills channel water downhill, Atlantic weather brings heavy bursts, and many properties were built long before modern drainage rules.
Problems that point to a drainage fault include:
Damp patches on walls, floors or in basements
Soft, boggy or squelchy lawns that stay wet for days
Water running across a driveway towards the house
Puddles at the base of downpipes
Driveway surfaces that sink or crack in wet areas
Garden walls that bulge or lean
Overflowing gutters and manholes during storms
Our article on how groundwork and drainage work together on a North Devon property explains why drainage should be planned at the start of a project and not left until the end.
Where Should Rainwater Go? The Drainage Hierarchy
Under Building Regulations guidance, surface water from a roof or paved area should be dealt with in a set order of preference.
Into the ground, via a soakaway or other infiltration system, where the soil allows it.
To a watercourse, such as a stream or ditch, where there is permission and a safe route.
To a surface water sewer, if one exists nearby, with the sewerage company's approval.
To a combined sewer, as a last resort and only with approval.
You cannot simply connect roof water to a foul sewer or put it wherever is convenient. Check with the building control team and the water company before connecting to any public sewer.
How Does a Soakaway Work?
A soakaway has three jobs: take in a lot of water quickly during a storm, store it temporarily, and release it slowly into the ground.
Traditional stone filled soakaway.
A pit is dug and lined with geotextile, then filled with clean, large stone. Water enters through a pipe, fills the gaps between stones, and soaks outwards through the sides and base.
Crate soakaway.
Modern systems use interlocking plastic crates wrapped in geotextile. Crates store far more water in less space than stone, because they are mostly void. They are lighter and quicker to build, and are now the common choice for domestic work.
Pipe or trench soakaway.
On some sites, a long perforated pipe in a gravel trench is used instead of a single pit, spreading water over a larger area.
Does Your Ground Suit a Soakaway? The Percolation Test
Not all soil drains. Clay holds water, and areas of thin soil over rock may not take it at all. Whether a soakaway is suitable is judged by a percolation or infiltration test, usually carried out following guidance in BRE Digest 365.
In outline:
A trial pit is dug to the depth the soakaway would be.
It is filled with water and left to drain.
The time taken for the level to drop between set points is measured.
The test is usually repeated to confirm the result.
The rate is used to calculate the size of soakaway required.
Poor results mean a standard soakaway will not work, and you may need a larger structure, a different drainage route, or an alternative such as discharging to a ditch or sewer with permission. A good local groundworker knows which parts of Ilfracombe and the surrounding villages tend to drain well and which do not, but the test on your plot is what counts.
Where Can a Soakaway Go?
Siting matters as much as size.
At least 5 metres from buildings. Water soaking close to foundations can weaken the ground or cause damp.
A safe distance from boundaries and neighbours. Guidance suggests about 2.5 metres, so water does not flow onto someone else's property.
Away from septic tank drainage fields, water supplies and boreholes.
Downhill of the building where possible.
Not under driveways, patios or parking where the load is heavy, unless it is designed for it.
Away from tree roots, which can invade and block systems.
On steep and cramped Ilfracombe plots, finding a legal position for a soakaway can be the hardest part. Sometimes the best answer is a different route altogether, such as a ditch connection, a larger shared system, or a storage tank with controlled release.
Soakaways for Driveways and Patios
Hard surfaces generate a lot of runoff. A 40 square metre driveway collects a surprising volume in a heavy downpour, and if it slopes towards the house or the road, that water causes harm.
Typical solutions for driveways are:
A linear channel drain across the entrance, catching water before it reaches the pavement or highway.
Gullies and pipes taking water to a soakaway.
Permeable surfacing, letting water pass through into a stone sub base that stores and releases it. This is common under permeable block paving and gravel with grids.
Falls towards a lawn or border, allowing natural soaking within the property.
Drainage also affects planning. Front gardens paved with impermeable surfaces over 5 square metres need either permeable materials or a drainage plan within the boundary. Our article on driveway planning permission and dropped kerbs in Devon explains the rule, and our guide to why proper drainage installation matters for driveways in North Devon covers the design side.
Land Drains and French Drains: Dealing with Wet Ground
Where the problem is water already in the ground, a land drain is a better tool than a soakaway.
How a French drain is built:
A trench is dug with a steady fall towards the outlet.
The trench is lined with geotextile.
A layer of clean stone is laid, and a perforated pipe sits on top, holes facing down or as the manufacturer directs.
The trench is filled with more stone, and the geotextile folded over the top.
The surface is finished with turf, gravel or soil, as the site needs.
The geotextile stops silt blocking the stone. Without it, a drain can silt up and fail within a few years.
Where land drains help
At the foot of a slope where water collects
Behind retaining walls, to relieve pressure
Along the edge of a patio or driveway
Across a wet lawn or sports area
Around a building to protect foundations from groundwater
The pipe has to run to a place where water can legally and safely go. A drain that just stops in the middle of a garden moves the problem a few metres sideways.
Drainage on Sloped Gardens
A hillside garden is both a challenge and an opportunity. Water gathers speed on a slope, but gravity is also free. A well planned drainage scheme uses it.
Typical measures include:
Cut off drains across the slope above a house or patio, intercepting water before it arrives.
Drainage behind retaining walls, using free draining stone and pipe.
Stepped terraces with drains at each level.
Swales or gentle channels guiding surface water along a planned route.
Our guide to sloped and uneven gardens in North Devon explains how levels and water are handled together on such sites.
Septic Tanks and Private Drainage: A Separate Matter
Soakaways for rainwater are not the same as drainage fields for foul water from toilets, sinks and washing machines. Septic tanks and drainage fields are regulated under the Environment Agency's General Binding Rules, and cannot be treated as an ordinary soakaway job.
If your property is off mains drainage, you need specialist advice, a correct percolation test, and often permission. We can prepare ground, excavate and backfill under the direction of the system designer or installer, but the design of foul drainage should be done by a qualified professional.
Installing a Soakaway: What Happens on Site
Here is how a typical domestic crate soakaway is built.
Step 1: Survey and test. Check levels, services, outlets and conduct the percolation test.
Step 2: Set out. Mark the position, keeping distances from buildings, boundaries and trees.
Step 3: Excavate. Dig to the design size and depth. A mini digger makes this quick and accurate. Our team can supply an operated digger where a machine is needed.
Step 4: Line the pit. Lay geotextile over base and sides.
Step 5: Bed and install. Place a bed of clean stone, set the crates, connect the inlet pipe with a silt trap or inspection chamber ahead of it.
Step 6: Wrap and backfill. Fold the geotextile over the top and backfill with clean stone and soil to the right depth.
Step 7: Reinstate. Replace topsoil, turf or surfacing. Mark the position of the access point on a plan.
Step 8: Record. Keep a drawing showing where it sits, which helps with future maintenance or a house sale.
Excavated material needs removing or reusing on site. Our guide to muckaway services in North Devon explains how spoil is handled.
Why Soakaways Fail
Most failures come from a handful of causes.
No percolation test, so the ground cannot absorb water.
Undersized for the roof or paved area.
Too close to a building, causing damp.
No silt trap, so sediment clogs the stone or crates.
No geotextile, letting soil wash into the voids.
Tree roots invading the system.
Blocked gutters and gullies, sending leaves and grit into the soakaway.
High water table, leaving no room for water to go.
Wrong materials, such as dirty stone or rubble.
A properly built soakaway should last for decades. A badly built one can fail in a few years.
Maintenance: Keep Water Moving
Drainage works quietly until it stops. A few simple checks protect it.
Clear gutters and downpipes at least twice a year, once in autumn after leaf fall.
Check silt traps and inspection chambers annually, and clear them when needed.
Keep gullies and channel drains free of leaves and grit.
Watch for slow draining or standing water after rain, which means something is blocked.
Keep trees and large shrubs away from drainage runs.
Do not build over inspection covers or soakaway access points.
Where a system has stopped working, jetting, camera surveys and local repair are often more sensible than starting again. A camera survey shows exactly where a pipe has collapsed, a root has entered, or a joint has failed.
Drainage and Your Building Project
Drainage touches almost every groundwork job.
Driveways.
Water must go somewhere other than the road or the house. See our article on driveway surfacing options in North Devon for how surfaces handle water differently.
Garages, sheds and extensions.
New roofs add runoff, and new bases need falls and gutters connected. Our guide to concrete bases for garages, sheds and extensions explains how drainage fits around a slab.
Block paving.
Poor drainage is a leading cause of sinking blocks, as we describe in our article on block paving repair and cleaning in North Devon.
Commercial sites.
Larger roofs and car parks need bigger and sometimes engineered systems, as described in our guide to commercial groundwork and site preparation across North Devon.
Choosing a Contractor for Drainage Work
Drainage is hidden work, so you rely on your contractor's honesty and skill. Ask:
Will you carry out a percolation test, and can I see the result?
How will the soakaway or drain be sized?
Where will water end up, and is that outlet permitted?
Will there be a silt trap and inspection access?
How will you handle services, trees and neighbours?
Can you provide a drawing of what is installed?
Our groundwork contractors team plans drainage as part of the whole job, so excavation, pipes, stone and surfacing work together. We have been doing this for over sixty years, and you can read why that history matters in our post on what six decades of North Devon groundwork means for homeowners.
Frequently Asked Questions
How far should a soakaway be from a house?
Generally at least 5 metres from buildings, and a safe distance from boundaries, to avoid damp and neighbour disputes. Always check the guidance that applies to your site.
Do I need permission to install a soakaway?
Often building control approval is needed, particularly when it is part of new work. You may also need permission if water is directed to a sewer or watercourse. Ask your local authority first.
What is the difference between a soakaway and a French drain?
A soakaway lets collected water soak into the ground. A French drain is a perforated pipe in a gravel trench that collects and carries water to another place.
Will a soakaway work in clay soil?
Often not well. Clay drains slowly, and a percolation test may show a standard soakaway is unsuitable. Alternatives include larger systems, storage with controlled release, or connection to an approved outlet.
How long does a soakaway last?
A well designed and maintained soakaway can last for decades. Silt, roots and poor installation shorten its life.
Can Crabb Contractors install soakaways and land drains in Ilfracombe?
Yes. We excavate and install soakaways, land drains and surface water systems across Ilfracombe and North Devon, and plan them alongside driveways, bases and paving.
Give Your Water Somewhere to Go
Good drainage is invisible when it works and obvious when it does not. A soakaway sized to the roof, sited on ground that has been tested, and protected by a silt trap, will do its job quietly for decades. A French drain run to a legal outlet will dry a wet lawn without moving the problem next door.
If you have a damp garden, a driveway that floods or a project that needs somewhere for rainwater to go, call Crabb Contractors on 01271 500072 or contact us online. We will visit the site, read the ground, and recommend a drainage plan that suits both the land and the weather of North Devon.
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