# Soakaway Sizer: BRE 365 Design — Percolation test & drainage

> Percolation test & drainage (iPhone/iPad app by Plan CD.)

- Source: https://appshunter.io/ios/app/soakaway-sizer-bre-365-design/id6805900057 (this page in markdown: same URL + `.md`)
- Developer: [Plan CD](https://appshunter.io/developer/309570233)
- Category: Utilities, Productivity
- Price: $9.99
- Age rating: 4+
- Requires: iOS 26.0 · 1 MB
- Languages: American English
- Released: 2026-09-14
- Data updated: 2026-09-15
- User reviews in markdown: https://appshunter.io/ios/app/soakaway-sizer-bre-365-design/id6805900057/reviews.md

## What is Soakaway Sizer?

Soakaway Sizer - The BRE 365 Calculation That Shows Its Working

Planning conditions and Building Control ask for a soakaway designed to
BRE Digest 365. The alternatives are a spreadsheet at your desk, a web
calculator that charges per report, or a consultant at several hundred
pounds per design. Soakaway Sizer runs the full BRE 365 method on your
phone, offline, next to the trial pit, and shows the chain of reasoning
behind every number so the design can be checked and defended.

HOW IT WORKS
Enter your percolation test results (pit dimensions and timed drop, or
an infiltration rate you already have), the impermeable area draining
to the soakaway, and the design rainfall. The app evaluates the
1-in-10-year storm across the full range of storm durations, takes the
worst case as BRE 365 requires, and sizes the storage - showing every
step, so you can check the working rather than trust a black box.

WHAT IT CALCULATES
- Soil infiltration rate f from your percolation test, with the lowest
  of your test runs governing the design
- Warnings when the ground is likely unsuitable for infiltration
- Required storage from the full storm-duration sweep, with the
  governing duration identified, not a single guessed storm
- Optional climate change uplift on design rainfall, as many local
  planning authorities now require
- Storage provided by crate/modular and rubble-filled constructions,
  using the appropriate void ratio, with manufacturer override
- Works both ways: enter dimensions and check compliance, or enter
  your site constraints and get suggested sizes

COMPLIANCE, LINE BY LINE
Clear pass/fail lines for the checks an inspector looks for: half
drain-down within 24 hours, minimum 5 m from buildings and 2.5 m from
boundaries per Approved Document H, and prompts for made ground and
groundwater.

WHO IT IS FOR
Groundworkers, drainage contractors, self-builders and builders dealing
with planning conditions, percolation tests and Building Control
submissions - and anyone who wants to see the method, not just the
answer.

A DESIGN AID, NOT A DESIGNER
Soakaway Sizer is a calculation aid. It does not replace the judgement
of a competent person, and every design should be verified by one
before construction. Calculations follow the method of BRE Digest 365
(2016); the app is not certified, approved or endorsed by BRE.

PRIVACY
No sign-in, no ads, no tracking. Works fully offline. Your data stays
on your device.


## Version history (last 1 release)

### 1.0 — 2026-09-15

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-15.*