The short answer
A soakaway in the UK typically costs £600–£3,000, with a domestic crate soakaway most often around £1,500–£2,500 installed. A soakaway is a buried pit or crate-filled void that lets collected water disperse slowly into the surrounding ground rather than running to a drain. The cost depends on the volume of water it must handle, the soil's ability to absorb it, the depth required and access for excavation. Free-draining ground needs a smaller, cheaper soakaway; clay that absorbs water slowly needs a larger one — and in heavy clay a soakaway may not work at all, so a percolation test is done first to check the ground can take it.
A soakaway is usually where a french or land drain sends its water. Its size, and therefore its cost, comes down to how much water it handles and how well your soil absorbs it.
Typical UK costs
- Soakaway range£600–£3,000
- Domestic crate soakaway~£1,500–£2,500
- What it isburied crate or pit
- Sized bywater volume + soil absorption
- Checked bya percolation test
What the cost depends on
- Water volume: the more roof or surface water it must take, the bigger the crate or pit and the higher the cost.
- Soil absorption: free-draining sandy soil needs a smaller soakaway; slow clay needs a much larger one.
- Depth & access: a deep soakaway, or one a digger can't reach, costs more to excavate.
- Percolation test: a small upfront cost that sizes the soakaway correctly and confirms the ground can take it at all.
| Item | Typical figure | Notes |
|---|---|---|
| Soakaway (overall) | £600–£3,000 | by size & ground |
| Crate soakaway (domestic) | ~£1,500–£2,500 | common modern approach |
| Percolation test | modest upfront cost | sizes & validates the soakaway |
| Larger / clay ground | higher end | needs more volume |
Indicative UK figures for guidance. Sources: MyJobQuote and Checkatrade cost guides.
When a soakaway is needed — and when it won't work
A soakaway is needed whenever collected water has no watercourse or surface-water sewer to be sent to — which is common in many gardens. But it relies on the surrounding ground being able to absorb water, so in heavy clay or a high water table a soakaway can fail, staying full and backing up. That is why a percolation test is carried out first: it measures how fast water drains from a test hole and tells the specialist whether a soakaway is viable and, if so, how big it needs to be. Building regulations and the Planning Portal also set out minimum distances from buildings, so siting matters.
Need a soakaway sized properly?
We'll match you with a vetted land drainage specialist who runs a percolation test, sizes the soakaway for your ground, and quotes it on a clear specification.
Frequently asked questions
How much does a soakaway cost?
Typically £600–£3,000 in the UK, with a domestic crate soakaway most often around £1,500–£2,500 installed. The size — and so the cost — depends on the water volume and how well your soil absorbs it.
What is a soakaway and how does it work?
A buried crate or pit that lets collected water disperse slowly into the surrounding ground instead of running to a drain. It relies on the soil being able to absorb water, so it suits free-draining ground better than heavy clay.
Do I need a percolation test for a soakaway?
Yes — a percolation test measures how fast water drains from a test hole, confirming whether a soakaway will work in your ground and sizing it correctly. In heavy clay or a high water table, a soakaway may not be viable at all.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific garden and ground. They are guidance, not a quotation.