Soakaway Problems: Signs, Causes and What to Do
In short
A soakaway takes surface water from roofs and hard standing and lets it disperse into the surrounding ground. Signs it is struggling include water lying above it after rain, gullies backing up, a permanently soft patch of lawn and damp at the base of walls. The usual causes are silt and debris carried in from gutters, a collapsed or crushed structure, saturated or heavy ground, and a system that is simply undersized for the area it drains. Confirming which needs an inspection of the pipework and the soakaway itself.
A soakaway is a void in the ground — traditionally rubble-filled, now more often a plastic crate structure wrapped in geotextile — that receives surface water and lets it soak away into the surrounding soil. It only works while two things hold true: water can reach it cleanly, and the ground around it can absorb what arrives.
Most failures come down to one of those two conditions changing, and the symptoms above ground look much the same whichever it is.
Signs a soakaway may not be working
Problems usually show up during and shortly after heavy rain, then disappear in dry spells, which is why they are often ignored for years.
- Water pooling on the ground above or near the soakaway after rain
- A gully or downpipe backing up and overflowing during a downpour
- A patch of lawn that stays soft, boggy or unusually green
- Water taking far longer to clear than it used to
- Damp or staining at the base of a nearby wall
- Surface water running towards the house rather than away from it
What causes a soakaway to stop draining
Several causes produce identical symptoms, and more than one is often present.
- Silt and debris — leaves, grit and roof detritus washed in from gutters gradually clog the voids and the surrounding geotextile.
- Blocked feed pipework — the soakaway may be fine while the pipe or gully feeding it is blocked.
- Structural failure — older rubble-filled pits settle and fill in, and crate systems can be crushed by vehicle loading if they were not built for it.
- Ground conditions — clay soils drain slowly, and a high winter water table can leave no capacity to absorb anything.
- Undersizing — extensions, conservatories and new hard standing added since the soakaway was built increase the volume it has to take.
- Root ingress and vegetation growing into or over the structure.
Why site conditions matter
A soakaway is only as good as the ground it sits in. The same design that copes easily in free-draining sand can fail on clay, and the same soakaway that worked for twenty years can be overwhelmed after a driveway is paved over or a roof area is extended.
Distance from buildings, boundaries and other structures also matters, as does the water table. Building Regulations Approved Document H covers drainage and waste disposal, including surface water disposal, and is the reference point for how surface water should be dealt with on a site.
What you can safely check yourself
There are useful checks that do not involve digging or entering anything.
- Clear gutters, downpipes and gully grates, then watch the system during the next heavy rain.
- Look for water standing above the soakaway once the rain has stopped.
- Check whether the problem also affects foul drainage — if it does, the issue is more likely to be the drain than the soakaway.
- Note whether anything has changed: new paving, an extension, a re-routed downpipe or a removed tree.
When an inspection is appropriate
If the feed pipework is clear and water is still standing, the soakaway itself needs assessing. That normally means jetting and a camera inspection of the pipe run to rule out blockage or collapse, then examining the soakaway's condition and how it sits in the ground.
Only after that is it sensible to talk about replacement, relocation or a larger structure — and the answer depends on soil type, the area being drained and what else is nearby. Do not dig trial holes or excavate around a soakaway yourself: excavations collapse, and services often run close by.
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