Percolation Testing in Warwickshire

Percolation Tests provides BRE365 soakaway percolation testing and foul infiltration testing across Warwickshire for planning applications, self-builds, and small developments.

Ground conditions in Warwickshire

Warwickshire sits largely on Mercia Mudstone (formerly known as Keuper Marl), a heavy clay-rich deposit that covers much of the county and tends to drain slowly. Some areas, particularly around river terraces near the Avon and Leam valleys, have sand and gravel deposits that percolate considerably better. Because of this contrast, soakaway feasibility varies plot to plot, and it’s common in Warwickshire for a percolation test to determine that an alternative drainage strategy, rather than a standard soakaway, is the right solution.

What we test for

• BRE365 percolation testing for surface water soakaway design
• Foul effluent infiltration testing (Part H) for septic tanks and treatment plants
• Drainage strategy (SuDS) support, working with civil engineering partners

Coverage across Warwickshire

We test across Warwick, Leamington Spa, Stratford-upon-Avon, Rugby, Nuneaton, Kenilworth, Bedworth, and the surrounding rural areas. Available Monday to Friday to fit around build schedules.

Why get a percolation test

Given the prevalence of slow-draining clay across much of Warwickshire, planning authorities routinely require BRE365 test evidence before approving drainage conditions — and a test can also save you from over-specifying (or under-specifying) a soakaway that won’t perform as expected.

Planning authorities in Warwickshire

Drainage conditions on Warwickshire planning permissions are set by the district or unitary council, and for larger schemes the Lead Local Flood Authority is consulted on the surface water strategy. Both expect infiltration to be considered first in the SuDS hierarchy and both expect the evidence to be a BRE Digest 365 test carried out on the site, not a figure taken from a map or a neighbour’s result. The authorities we most often write reports for in Warwickshire are:

• Warwickshire County Council — the Lead Local Flood Authority, consulted on surface water drainage for larger applications across all five districts
• Warwick District Council — Warwick, Leamington Spa, Kenilworth and Whitnash
• Stratford-on-Avon District Council — Stratford, Alcester, Shipston and the rural south
• Rugby Borough Council
• Nuneaton and Bedworth Borough Council
• North Warwickshire Borough Council — Atherstone, Coleshill, Polesworth

If your decision notice asks for ‘infiltration testing in accordance with BRE 365’, ‘evidence of soakaway feasibility’ or ‘percolation test results to BS 6297’, that is what we produce, laid out so the case officer can find what they need without asking again.

Ground conditions in more detail

Most of the county is Mercia Mudstone, and it is worth being blunt about what that means: a conventional soakaway is often not viable, and the test is what proves it either way. The pattern breaks in three places. The Avon, Leam and Sowe valleys carry terrace sands and gravels that can drain well; south of the Fosse Way the mudstone gives way to Lias clay, which is slower still; and around Nuneaton and Bedworth the Warwickshire coalfield leaves made ground and old workings where a result in one pit says little about the next. Where a soakaway fails, a measured rate is still what the drainage engineer needs to size attenuation or to make the case for a watercourse or sewer connection.

Which test does your site need?

A BRE 365 test sizes a surface water soakaway — roof and driveway run-off — and is what Approved Document H3 and the SuDS hierarchy point to. A BS 6297 test sizes a foul drainage field for a septic tank or package treatment plant under Approved Document H2. They use different pits, different procedures and different calculations.

The rural south and the villages between the towns are largely off the mains foul sewer, so treatment plants and septic tanks with drainage fields are common. Those drainage fields are sized from a BS 6297 test, which is not the same as the BRE 365 soakaway test and cannot be substituted for it — a drainage condition asking for one is not discharged by the other. Sites needing both get both on a single visit.

What our testing in Warwickshire shows

We have carried out more than 50 tests within a dozen miles of the Warwickshire towns listed below since 2018. Of the sites where we recorded an outcome, well over half did not achieve an infiltration rate that would support a conventional soakaway. That is not a reason to skip the test — it is the reason to do it early. A measured rate, even a poor one, is what your engineer needs to size attenuation or justify a different discharge, and it is what the authority will accept. A guessed rate is what gets a scheme sent back.

What you receive

• A full report with the recorded times for every pit and every fill
• The calculated infiltration rate, ready to hand to your engineer or planner
• Trial pit locations and depths
• Photographs of the testing on site
• A clear statement of whether a soakaway is viable, and if not, why not

Get a quote

Contact us for a free, no-obligation quote for percolation or infiltration testing anywhere in Warwickshire. Call 01902 475653 or request a quote online.

Towns and areas we cover in Warwickshire

• Warwick — Avon terrace gravels by the river, mudstone above; 21 tests within ten miles
• Leamington Spa — Leam valley gravels next to slow clay; 19 tests within ten miles
• Stratford-upon-Avon — Avon terraces in town, Lias clay to the south; 14 tests within ten miles
• Rugby — Lias clay and mudstone; marginal results are common; tested nearby
• Nuneaton — coalfield made ground and old workings; 9 tests within ten miles
• Kenilworth — sandstone outcrops give better odds than the surrounding mudstone; 22 tests within ten miles

Recent work near Warwickshire