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Install a new soakaway.
Crate or rubble soakaway — sized to roof area and ground percolation, to current Building Regs.
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Costs, timelines, pitfalls and the right questions to ask before any drain specialist starts on soakaway Installation.
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Undersized soakaway
Cheap quotes use "rule of thumb" without percolation test. Clay soils need bigger soakaway.
Crate crushed
Driven over by car. Use car-rated crates.
Geotextile missing
Without wrap, silt clogs crate within 3-5 years.
Too close to building
Within 5m can cause subsidence in clay soils.
Costs & timeline
Know what it costs. Know when it ends.
Indicative UK ranges and what affects price.
Cost range
By job type
Inc. VAT · 2026
Source: NMT quotes
Source: NMT quotes
Percolation testOne-day site visit
£100–£250
Stormcrate (1m³)Material only
£80–£180
Geotextile membrane3-6m²
£30–£80
Excavation (1.5-2m deep)Mini-digger
£200–£500
Connection pipe and inspection chamber110mm pipe
£120–£300
Standard 1m³ soakaway installDomestic small
£500–£1.2k
!
Quote spread is typically ± 18% — always get 3 quotes.
At a glance
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Soakaway disperses rainwater into the surrounding subsoil — required where no surface-water drain available. Expect to pay £500–£2,500 for UK domestic soakaway.
What Does the Work Involve?
Installer digs pit (5m+ from house, 2.5m from boundary). Pit sized via percolation test. Plastic crates wrapped in geotextile (95% void). Older soakaways used gravel (30% void). Downpipe connected via buried pipe 1m below ground. Pit backfilled.
Typical Costs
| Item | Low (£) | High (£) | Notes |
|---|---|---|---|
| Percolation test | 100 | 250 | One-day site visit |
| Stormcrate (1m³) | 80 | 180 | Material only |
| Geotextile membrane | 30 | 80 | 3-6m² |
| Excavation (1.5-2m deep) | 200 | 500 | Mini-digger |
| Connection pipe and inspection chamber | 120 | 300 | 110mm pipe |
| Standard 1m³ soakaway install | 500 | 1,200 | Domestic small |
| Larger 2-3m³ soakaway | 1,000 | 2,500 | Heavy clay or large house |
How Long Does It Take?
Percolation test: half day + 1-2 days lag. Excavation and install: 1-2 days. Reinstatement: 1 day. Total: 4-5 days.
DIY or Professional?
DIY for confident builder with mini-digger. Professional gives warranty and right sizing.
Choosing the Right Tradesperson
Drainage contractor or groundworker. NADC member. Confirm crate brand (Stormcrate, Polypipe, Hydrocrate).
UK Regulations
Approved Document Part H covers soakaway design. BRE Digest 365 sizing guide. 5m+ from buildings, 2.5m+ from boundary.
Common Problems
- Undersized soakaway: Cheap quotes use "rule of thumb" without percolation test. Clay soils need bigger soakaway.
- Crate crushed: Driven over by car. Use car-rated crates.
- Geotextile missing: Without wrap, silt clogs crate within 3-5 years.
- Too close to building: Within 5m can cause subsidence in clay soils.
Frequently Asked Questions
When do I need a soakaway?
When no public surface-water drain available, or extending and existing drain overloaded. Increasingly new builds use soakaways under SuDS policy.
How big should soakaway be?
Sized from percolation test. Rule of thumb: 0.5-1.5m³ per 25m² roof in average UK clay soils.
Crate or gravel?
Crates — 95% void in small footprint. Gravel obsolete except for very small applications.
Can I drive over soakaway?
Yes if crate rated for vehicle load. Polystorm Lite: foot only. Polystorm Access: car-rated.
How long does soakaway last?
25+ years on crate (warranted). Geotextile wrap, no silt entry, lifetime indefinite.
Do I need a percolation test?
For sizing, yes — without it the soakaway is guesswork. £150 saves £000s on wrong sizing.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
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