Soakaway not draining: diagnosis and fix
Water pooling on the lawn or driveway after rain? Your soakaway has failed. Here's why, and what your options are.
If water sits on your lawn or driveway for hours after rain stops, your soakaway has stopped soaking away. There are three usual culprits.
1. Silted up
The gravel pit (or crate) has clogged with fine silt and roots over many years. Common in soakaways more than 20 years old.
Test: Jet the surface-water run and the soakaway inlet. If water flow improves dramatically for a few weeks then slows again, silting is your cause.
Fix: Either deep jetting and vacuum extraction (cheap, partial result) or excavate, replace the gravel/crates and re-wrap with geotextile.
2. Crushed plastic crate system
Modern soakaways use plastic 'crates' wrapped in geotextile membrane. Under driveways they can collapse if installed without adequate cover or with the wrong load-rating crate.
Test: Sudden failure (months not years) under a driveway = crushed crate, almost certainly.
Fix: Excavate and replace with a higher load-rating crate, or restore the gravel-pit design.
3. Wrong location for soakaway to work
- Too close to the house (less than 5m)
- Heavy clay sub-soil (low percolation rate)
- High water table
- Below the level of the surface-water run feeding it
Test: Dig a 1m test pit nearby. Fill with water. If it doesn't drain away within 24 hours, the ground won't soak no matter what soakaway you fit there.
Fix: Relocate the soakaway to better ground, or convert to a surface-water connection if the local sewer permits.
Typical costs
- Jet + vacuum extraction (recovery attempt): £200–£400 + VAT
- Replace single domestic crate soakaway: £1,500–£3,000 + VAT including excavation, crates, geotextile, gravel and reinstatement
- Soakaway relocation: quoted on inspection
Part H of the building regs requires a percolation test before a new soakaway. We can do this as part of any replacement quote.