Soakaways: how they work and problems encountered...

Soakaways are used for the disposal of water to ground. There can be storm water soakaways, septic tank soakaways, sewage treatment plant soakaways and trade effluent soakaways. The only type of foul water drainage system which does not utilises soakaways are cesspools, sealed units.


Types of soakways

Domestic soakaway

a) Storm water soakaway

 i) Infiltration unit soakaways

 ii) Trench soakaways

  Herring bone soakaways

  Looped soakaway

 iii) Concrete ring slab

b) Septic tank soakaways

 i) Infiltration unit soakaway

 ii) Trench soakaways

 iii) Combination of soakaways

c) Septic tank soakaways

 i) Infiltration unit soakaway

 ii) Trench soakaways

 iii) Combination of soakaways

Commercial soakaway

a) Trade effluent soakaway

b) Storm water soakaway

c) Sewage Treatment Plant soakaway

d) Septic tank soakaways

e) Interceptor soakaway




The installation of soakaways, the design of soakaways and the construction of soakaways are governed by the Environment Agency

The size of soakaway required is dependent upon the permeability of the ground, therefore the slower the drainage the larger the soakaway area needs to be. Volume of water discharged also dictates the size of soakaway.


Legislation for the construction of soakaways, specifically domestic soakaways is changing, due to the increase in water consumption per person and historical rainfall data. Recently it has been found that domestic foul water drainage soakaways have been failing due to these factors.


It is important to note that all storm water soakaways will fail at some time due to the fact that we cannot control the volume of water falling onto the soakaways catchment area. There is a minimum design requirement for a soakaway serving a rainwater down pipe as set out in building regulations. However in a storm water soakaway design, catchment area, ground permeability and frequency and strength of storm need to be taken into account. Cost is always a governing factor in storm soakaway designs, especially for domestic soakaways. However should a surface / storm water soakaway fail it is not an initial health hazard, which would be the case with a foul water drainage soakaway.


In very poor ground conditions some soakaways may be installed to act as a filter bed / filter soakaway prior to discharge to a drainage ditch or water course.

Important factors to remember with soakaways

  • All soakaways will fail at some stage
  • All soakaways to be designed in accordance with Environment Agency regulations
  • All soakaways to be designed with building regulations
  • Soakaways come in various designs to suit different requirements
  • Unless mains drains are available your drainage will need a soakaway

Finally on an environmental note, all water should discharge to soakaways rather than drains as they directly return the water to ground and in turn aquifers.




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The Drain Experts unblock soakaways and drains and service and repair your sewage plant, cesspitt, broken drain pipe, broken drains and domestic sewage treatment plant. We also provide sewage treatment

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