Visual Soakaway Design Version 4 incorporates the best of BRE 365 and CIRIA 156 in design methodologies for infiltration systems.

  • 3D modelling Visual Design Window gives designers true flexibility and freedom to design a soakaway that is sized appropriately for their project.
  • Flat (or Plane) soakaways can be designed for sites where porous paving is needed.
  • In accordance with the requirements of the Environment Agencies Filter Trenches can designed to aid in providing sustainable solutions to urban (and rural) drainage project.

The Visual Design Window

The designer can now see and manipulate a visual representation of either a trench or ring soakaway. The visual soakaway can be moved anywhere within the window and designed in real-time thus reducing the total design time.

Filter Trench Design Option

In addition to the soakaway design functionality, the designer may opt to design a filter trench. A filter trench is essentially the same as a soakaway except that a specified portion of the surface runoff is allowed to discharge through an overflow pipe. In this way, surface water from a site can be treated by infiltration through the fill media prior to discharge to a watercourse and also removes the need for total storage within a traditional soakaway.

Soakaway Maintenance Schedule

Due to the importance of maintenance, we have produced a schedule which can be printed off and kept on file to allow the useful life of the soakaway to be monitored. A free soakaway Maintenance Schedule can downloaded here from our Downloads page.

Ring Soakaway Surrounding Fill and Margin Variable
Version 4 also includes the option of including the granular fill surrounding the ring soakaway for storage purposes. This allows for a slight reduction in depth in the finished design.

The Margin variable has been introduced to account for the width around a Precast concrete ring soakaway which may be filled with granular fill material. The Margin variable is set in the Design Options window as shown below.

Z1 and Z2 Factors

In keeping with the design methodology of the BRE 365, the design rainfall can be calculated to a more accurate statistical level using the Z1 and Z2 factors for various regions of the UK.

Flat Soakaway or Base Infiltration Option

In Version 4 the designer has the option of including the base of the trench soakaway in his/her design, thus making it possible to analyse the behaviour of a permeable surface for surface water drainage. eg. porous block paving.

Failure Depth of the Ring Soakaway

Previously the failure depth of ring soakaways was set to 4 metres. This is now entirely at the designers discretion and can be modified at design time. However, the failure half emptying time is still set to 24 hours.

Factor of Safety

The factor of safety coefficient has been included to allow the designer greater margins of comfort in sites where flooding is an issue. The infiltration rate of the soil is divided by the factor of safety within the design calculations and, therefore, increases the overall size of the soakaway.

Soil Infiltration Table

This feature must be used with caution!

The table is provided purely as a guide to allow for a rapid nominal design based on an estimated infiltration rate. It is vital, for a soakaway to work effectively for its design life, that a porosity test is carried out on site.

AutoCAD Drawings

AutoCAD drawings of typical soakaway arrangements are included in the full version of Visual Soakaway Design 4. These can also be freely downloaded from our Help pages.

System Requirements

IBM Compatible 486MHz (or higher)16Mb RAM minimum HDD with 7Mb of free disk space
Double-speed CD ROM drive or higher
Windows 95, 98, ME, NT, 2000, XP, Vista compatible