How Much Does a Percolation Test Cost?
Quick Answer
Roughly £100–£300 for the percolation test alone, £300–£800 for a fuller site assessment or full site investigation
2026 UK estimates for the standard Approved Document H test (2–3 trial holes). Most homeowner quotes land around £300–£500; a specialist national installer’s test starts from about £500–£600 including VAT. The higher tiers likely reflect a fuller site evaluation and, in some cases, a written report, though the published price guides don’t itemise exactly what each tier includes. Prices vary by region, number of holes and site access, so always get written quotes locally, these are estimates, not a quote.
Percolation Test Costs by Scope (2026 UK)
The price depends almost entirely on how much is included beyond the test itself: a bare reading you interpret yourself costs far less than a fully reported test a Building Control body will accept. The ranges below collate MyBuilder’s 2026 groundwork price guide, the UK septic-system knowledge base Housey, and Premier Tech Aqua, a national UK septic installer.
| Scope | Guide price | Notes |
|---|---|---|
| Percolation test only | £100–£300 | MyBuilder’s own description: a soil test to determine drainage suitability. In practice that typically means 2–3 hand-dug trial holes per Approved Document H’s own minimum, with no formal written report at this tier |
| Percolation test with site assessment | £300–£600 | Adds an initial evaluation of ground conditions for the drainage field, still short of a full engineered report (MyBuilder 2026) |
| Full site investigation | £300–£800 | Percolation test plus wider site investigation combined into one job (Housey UK septic tank installation guide, 2026) |
| Specialist test, national installer | From £500 + VAT (≈£600 inc. VAT) | Premier Tech Aqua’s published starting price for a percolation test; the separate groundwater trial hole is quoted per site, not a fixed fee |
| This site’s own typical range | £100–£600 | Most quotes £300–£500 (our percolation test calculator’s own sourced estimate); use the calculator itself for free once you have readings |
What the Test Actually Involves
Whatever the price, a compliant percolation test follows the same Approved Document H 2015 method (§1.34–1.37): excavate a 300mm square hole to 300mm below the proposed pipe invert, fill it and let it drain away overnight as a pre-soak, then refill the next day and time the fall from 75% full to 25% full, a 150mm drop. That reading is repeated at least three times across at least two trial holes and averaged into a percolation value, Vp, in seconds per millimetre. Because the method needs an overnight gap, most contractors price in two site visits, not one, which is a large part of why a bare test rarely comes in under £100.
Why the Price Range Is So Wide
- Number of trial holes: Approved Document H sets a minimum of two holes and three readings; larger sites, an inconclusive first result, or more than one proposed drainage field all mean more holes and more time on site
- Written report or not: a number scribbled on site costs little; a report a Building Control body will accept alongside your BS 6297:2007 drainage field design costs more. Published price guides don’t itemise exactly what each tier includes, but a formal report is a reasonable driver of the higher figures
- The separate groundwater trial hole: Approved Document H §1.32–1.33 also requires a preliminary trial hole, at least 1m² and 2m deep (or 1.5m below the proposed pipe invert), to check the water table doesn’t rise within 1m of the drainage pipes. This is a bigger dig than the percolation holes themselves and specialist firms such as Premier Tech Aqua quote it separately per site rather than as a fixed add-on
- Access and travel: a firm travelling further, or a site needing hand-digging because machinery can’t reach, adds time
- Region: contractor day rates set the floor under every quote; see below
Can I Do a Percolation Test Myself?
Yes. The Approved Document H method only needs a spade or 300mm auger, a tape measure, water and a stopwatch, and our free percolation test calculator turns your own timed readings straight into a Vp value and checks it against the 12–100 seconds-per-millimetre range a drainage field needs (§1.38). Doing it yourself avoids the test fee entirely. What you can’t skip is the separate groundwater trial hole, and most Building Control bodies still want a written report alongside your drainage field design, which is why many homeowners pay a professional for the accuracy and the paperwork rather than the digging itself.
Labour Behind the Price
Where a contractor does charge a day rate rather than a fixed test fee, UK groundworker rates for 2026 run £180–£280 per day nationally, £240–£350 per day in the South East, and £280–£400 per day in London, labour only. If a mini-digger is needed for the deeper groundwater trial hole rather than hand-digging, plant hire adds a further £150–£300 per day on top, or £350–£500 per day for a larger 3-tonne machine (whattocharge.co.uk, 2026 UK trade rate guide).
London and the South East
As with most groundworks pricing, London and South East quotes sit at the top of every range above: the higher day rates that push a full site investigation towards £800 are far more likely in those regions than in the rest of the UK, where the typical £300–£500 band is more representative.
Don’t Skip It to Save the Fee
A percolation test is not optional paperwork. Under the Environment Agency’s General Binding Rules, treated effluent discharged to ground must pass through a drainage field designed to BS 6297:2007, and Approved Document H requires the site assessment, trial hole and percolation test before that field can be sized. Skipping the test risks a drainage field that is undersized (frequent blockages, effluent surfacing) or that Building Control simply refuses to sign off. Once you have a Vp reading, size the field itself with our percolation test calculator, or the soakaway equivalent for surface water with our soakaway sizing calculator to BRE Digest 365. If you also need to route the drain itself, check how deep drainage pipes need to be buried under Approved Document H Table 10.
Important Notes
- All figures are 2026 UK guide prices from published sources, not quotes: get at least two or three written quotes covering the same scope before budgeting
- A percolation test alone doesn’t size your septic tank or drainage field, that’s a separate calculation once you have the Vp value
- Excludes VAT unless stated; Premier Tech Aqua’s £500 starting price is explicitly quoted excluding VAT
- Don’t test in heavy rain, severe frost or drought, Approved Document H §1.37 flags abnormal weather as a reason a result can’t be relied on
Figures cross-checked against MyBuilder’s groundwork and septic tank cost price guide, Housey’s UK septic tank installation knowledge base, Premier Tech Aqua’s published soil testing pricing, and whattocharge.co.uk’s 2026 UK groundworker day rate guide, all fetched July 2026. Test method and suitability thresholds verified against Approved Document H 2015 §1.32–1.44 and BS 6297:2007. Last updated: July 2026.