Do the calculations in Visual Soakaway Design 4 follow BRE 365 or CIRIA 156 documents?

Visual Soakaway Design 4 incorporates the best of BRE 365 and CIRIA 156. The Design methodology follows all of the BRE 365 guidelines and includes many other features such as “Factor of Safety”, user definable failure parameters.

The most recent release of our software includes many new features not previously seen. For further details on new features click here.

What is the basic design theory underlying soakaway design?

The basic theory of Soakaway design follows the formula shown below…

Storage = Inflow - Outflow


Storage = the amount of water that can be stored within the Soakaway.

Inflow = the total defined runoff from the impermeable area (taking into account the volumetric runoff coefficient and any deduction for filter trench design).

Outflow = (surface area of exfiltration) x (soil infiltration rate) x (storm duration).

Full details of our design methodology can be found in the Help files here.

I see that Visual Soakaway Design 4 designs filter trenches. How does it do that?

Visual Soakaway Design 4 designs filter trenches in the same way that it designs soakaways, however, when the designer chooses the filter trench option he/she must select a percentage of the impermeable area which will overflow out of the soakaway. In doing this, the majority of the volume is still infiltrating into the ground with only a predefined amount being released into the watercourse. This attenuation protects the integrity of the watercourse from excessive erosion.

From an environmental viewpoint, can Visual Soakaway Design 4 help me with designing sustainable drainage systems on new developments?


Visual Soakaway Design 4 can design Filter Trenches which give the following benefits to new developments…

  • Surface water run-off from road and hard-standing areas can be filtered within the trench, thus allowing only a predefined volume of water to discharge to the watercourse or surface water sewer.
  • The use of filter trenches provides attenuation during the storm event. This lessens the impact of drainage from new developments on the watercourse thereby protecting rivers from excessive siltation and erosion.
  • Soakaways are constructed underground and, therefore, do not impact visually on the final landscaped surface.

Can Visual Soakaway Design 4 design infiltration systems that use “Stormcell” units?


Visual Soakaway Design 4 has a user-definable setting for the Void Ratio of the soakaway. This can be set as high as 0.95 which is comparable to that found in Stormcell units produced by HRD Ltd.

What extras do you get with the full version that the evaluation doesn’t have?

The full version of Visual Soakaway Design 4 includes the following features…

  • Full file open/save/print functions.
  • Unlimited use plus full technical support.

I see that there is a disclaimer on the software regarding maintenance of soakaways. What does this mean?

WebCom Systems include this disclaimer due to the importance of maintaining the soakaway throughout its useful life.

Soakaways can become clogged with silt through time and regular monitoring of silt levels must be carried out. The use of a silt trap manhole at the head of a soakaway can, however, greatly reduce the inflow of silt and suspended solids.

As an aid to the designer, we now include a maintenance schedule with version 4.

If I buy Visual Soakaway Design 4 what kind of after-sales support can I expect?

WebCom Systems will respond to all queries whether by telephone or email in 2 working days. We can be contacted at any time on 07050 184360. Click here to email us direct.

Is there any other comparable product on the market today?


Visual Soakaway Design 4 has a visual design window which allows designers to see a 3D representation of the soakaway and stretch it while designing it in real-time.

We have been in the soakaway software market for over 10 years now and aim to remain the preferred supplier of such software.

How much does Visual Soakaway Design 4 cost?

Visual Soakaway Design 4 is currently priced at £399 for the download version.
An Activation key will be issued on purchase to activate the software.

If you would like to order a copy please click here…