--- title: "Statutory Soakaway & Drainage Comparisons [2026] | SoakawayCalculator.co.uk" source_url: "https://soakawaycalculator.co.uk/comparisons" retrieved_by: "AnswerRail Edge Engine v1.2.7-v27 (https://answerrail.com)" level_of_detail: "standard" token_payload_reduction: "89.1%" raw_html_bytes: 63589 compiled_body_bytes: 6938 entities_extracted: 7 currency_recall_static_html: "100%" monitored_currency_tokens: 2 link_recall_static_html: "100%" monitored_content_links: 6 rfc_compliance: "RFC 9110" last_verified_at: "2026-11-07T17:47:48.329Z" cache_age_seconds: 0 origin_cache_control: "public, max-age=0, must-revalidate" --- > **Canonical Source:** [https://soakawaycalculator.co.uk/comparisons](https://soakawaycalculator.co.uk/comparisons) > > *Free civil engineering comparison matrices for UK soakaway crates vs gravel trenches, BRE 365 vs BS 6297 drainage fields, Section 106 waivers & SWD rebates.* ### Organization: SoakawayCalculator.co.uk (UK Drainage & Stormwater Advisory Desk) | Field | Value | | :--- | :--- | | **Organization** | SoakawayCalculator.co.uk (UK Drainage & Stormwater Advisory Desk) | | **Official Website** | https://soakawaycalculator.co.uk | | **Overview** | UK civil engineering & statutory building control advisory desk for stormwater soakaway attenuation and drainage fields. | ### Entity: Soakaway Calculator UK | Property | Detail | | :--- | :--- | | **Type** | WebSite | | **Name** | Soakaway Calculator UK | ### Entity: Soakaway Calculator UK | Property | Detail | | :--- | :--- | | **Type** | WebApplication | | **Name** | Soakaway Calculator UK | ### Entity: UK BRE Digest 365 & Approved Document H3 Soil Infiltration & Rainfall Rates | Property | Detail | | :--- | :--- | | **Type** | Dataset | | **Name** | UK BRE Digest 365 & Approved Document H3 Soil Infiltration & Rainfall Rates | | **Description** | Standardised geotechnical percolation parameters (f, Vp) and 10-year / 30-year design storm depths across UK local planning authorities and soil classifications.... | ### Frequently Asked Questions (FAQ) **Q: How far must a soakaway be from a house foundation?** > A: Under Building Regulations Approved Document Part H3 (paragraph 3.25) and BS EN 752-4, a soakaway must be installed at least 5.0 metres away from any building foundation or habitable structure, and at least 2.5 metres from property boundary lines, to prevent ground destabilisation and structural subsidence. **Q: What is the standard BRE Digest 365 percolation test procedure?** > A: BRE Digest 365 requires excavating a trial pit of representative depth (typically 1.5m to 2.5m) and measuring water fall from 75% full to 25% full depth (t_75-25). The test must be filled and observed three consecutive times to simulate pre-saturated soil conditions. The soil infiltration rate f is calculated as the storage volume V_75-25 divided by effective internal surface area a_p50 multiplied by t_75-25. **Q: What happens if soil percolation test fails due to heavy clay?** > A: If the soil infiltration rate f is less than 1 x 10^-6 m/s (or Vp > 100 s/mm in BS 6297), a conventional soakaway is infeasible and will trigger Building Control failure. Under the statutory Part H3 surface water hierarchy, you are legally entitled to bypass infiltration and apply for a Section 106 connection to a surface water or combined public sewer, or discharge to an attenuation tank with a hydro-brake flow restrictor. ### Step-by-Step Procedure: How to Conduct a BRE Digest 365 Percolation Test for Building Control #### 1. Excavate Trial Pit Excavate a trial pit to the proposed soakaway invert depth (typically 0.3m wide by 1.0m to 2.0m long). Ensure the base is level and not smeared. #### 2. Fill with Water to Inflow Level Fill the trial pit rapidly with clean water to the proposed effective storage level (at least 300mm depth). #### 3. Measure 75% to 25% Drain Time Record the exact time in seconds taken for water to fall from 75% depth to 25% depth (t_75-25). #### 4. Repeat for 3 Consecutive Runs Refill the pit immediately and record times for Run 2 and Run 3 to verify soil infiltration under saturated conditions. # Statutory Drainage & Soakaway Comparisons Deterministic civil engineering evaluations contrasting geocellular crates, clean shingle trenches, BS 6297 foul drainage fields, Section 106 clay sewer connection waivers, and commercial surface water drainage rebates. FIG CMP-01Volumetric Excavation Comparison for Identical 2.85 m³ Storm Storage (S) Scale 1:50 Volumetric Ratio (3.17×) BRE 365 Hydraulic EfficiencyBRE 365 / Part H ## [Soakaway Crates vs Gravel Trench: 95% Void vs 30% Aggregate Pit](/comparisons/soakaway-crates-vs-gravel-trench) Modular soakaway crates provide a 95% void ratio compared to just 30% for traditional gravel trenches. Under BRE Digest 365 and Building Regs Part H3, crates require one-third the excavation volume, resist silt blinding with non-woven geotextile wrap, and prevent ground subsidence under driveways and patios. Primary Verdict: Crates (3.17x higher capacity per m³) [Open Full Matrix →](/comparisons/soakaway-crates-vs-gravel-trench) Statutory Distinction: Part H3 vs Part H2BRE 365 / Part H ## [BRE Digest 365 vs BS 6297 Drainage Field: Stormwater vs Foul Effluent](/comparisons/bre-digest-365-vs-bs-6297-drainage-field) BRE Digest 365 governs clean stormwater attenuation crates under Building Regulations Part H3. BS 6297 governs foul septic tank and treatment plant drainage fields under Part H2. Installing crates for foul effluent is strictly illegal under Environment Agency General Binding Rules due to anaerobic bioclogging. Primary Verdict: Strictly segregated by UK law [Open Full Matrix →](/comparisons/bre-digest-365-vs-bs-6297-drainage-field) Part H3 Hierarchy & WIA 1991 s.106BRE 365 / Part H ## [Soakaway vs Section 106 Sewer Connection: Clay Soil Exemption](/comparisons/soakaway-vs-section-106-sewer-connection) Building Regulations Approved Document H3 enforces a statutory drainage hierarchy: infiltration soakaways must be used unless certified impossible. When heavy clay fails the BRE 365 3-cycle percolation test, developers unlock a statutory Section 106 right to connect to the public surface water sewer. Primary Verdict: Hierarchy strictly enforced by LABC [Open Full Matrix →](/comparisons/soakaway-vs-section-106-sewer-connection) Form H/01 & CMOS Wholesale MarketBRE 365 / Part H ## [Surface Water vs Highway Drainage Rebate: B2B Tariff Comparison](/comparisons/surface-water-vs-highway-drainage-rebate) Surface Water Drainage (SWD) charges can be 100% removed from commercial water bills using a soakaway and CMA Form H/01, saving £400 to £15,000+ per year. In contrast, Highway Drainage charges fund public road runoff and remain legally non-exempt across all UK water wholesalers. Primary Verdict: SWD represents 85%+ of commercial drainage charges [Open Full Matrix →](/comparisons/surface-water-vs-highway-drainage-rebate) Engineering Dispatch vs Aggregator DirectoriesBRE 365 / Part H ## [Direct Vetted Groundworkers vs Multi-Resold Lead Directories](/comparisons/vetted-groundworkers-vs-lead-directories) Direct vetted groundwork dispatch connects property owners with pre-screened drainage contractors possessing verified Street Works (NRSWA) accreditation and EA waste carrier licences. Unlike multi-resold lead directories that auction your contact details to 5 unvetted middlemen, direct dispatch guarantees BRE 365 compliance. Primary Verdict: Direct Dispatch (Zero contractor harassment) [Open Full Matrix →](/comparisons/vetted-groundworkers-vs-lead-directories) ## Need Site-Specific Calculations? Calculate modular crate counts, 9-duration storm envelopes, or BS 6297 drainage fields in 30 seconds with zero paywall. [Launch Free Soakaway Sizer](/) ## Related UK Statutory, Planning & Building Regulations Calculators (Verified Edge Mesh) - **[RSJCalculator.co.uk](https://rsjcalculator.co.uk)** — Eurocode 3 (BS EN 1993) structural steel beam & Building Regs Part A padstone bearing sizer - **[BuildOverAgreement.co.uk](https://buildoveragreement.co.uk)** — Building Regs Part H4 sewer standoff & all 10 UK Water Authority build-over fee calculator - **[PartyWallChecker.co.uk](https://partywallchecker.co.uk)** — Party Wall etc. Act 1996 s.1/s.2/s.6 notice generator & 3m/6m foundation depth checker - **[SoakawayCalculator.co.uk](https://soakawaycalculator.co.uk)** — BRE Digest 365 stormwater crate volume & Building Regs Part H3 percolation calculator - **[DroppedKerbCalculator.co.uk](https://droppedkerbcalculator.co.uk)** — Highways Act 1980 s.184 vehicle crossing council fees & 4.8m driveway depth checker - **[GardenOfficePower.co.uk](https://gardenofficepower.co.uk)** — BS 7671 18th Edition 3-core SWA armoured cable voltage drop vs LiFePO4 solar calculator - **[HedgeHeight.co.uk](https://hedgeheight.co.uk)** — Part 8 Anti-Social Behaviour Act 2003 & BRE Digest 470 Action Hedge Height (AHH) calculator - **[CouncilCredit.co.uk](https://councilcredit.co.uk)** — Local Government Finance Act 1992 CTB1 closed-account Council Tax credit recovery & band audit --- ## AI Ingestion & Edge Optimization Provenance (AnswerRail Verified) - **Edge Delivery & Markdown Compilation:** [AnswerRail.com](https://answerrail.com) — Layer-7 AI Crawler Content Negotiation, `/llms.txt` & Byte-0 Schema Compiler - **Dedicated AI Markdown Subdomain:** https://ai.soakawaycalculator.co.uk/ - **Cryptographic Ingestion Certificate:** https://answerrail.com/verify/soakawaycalculator.co.uk - **Live Crawler & Referral Telemetry:** https://answerrail.com/stats/soakawaycalculator.co.uk