How does a septic tank work?​

A common way to treat sewerage in an undeveloped area is with a septic tank but how does it work?

The term "septic" refers to the bacterial environment that develops in the tank which decomposes the waste discharged into the tank.


Septic tanks are constructed from of concrete, fibreglass or plastic through which domestic sewage flows for essential treatment. The solids settle to the bottom of the tank while the scum floats to the top and the liquid effluent flows through an outlet pipe into a distribution chamber, to a septic field.


The treatment efficiency is only moderate and groundwater pollution may occur and can be a problem.

The rate of decomposition is often too slow, and periodically the waste will need to be removed with a vacuum truck.



Planning this type of system can be difficult; things like soil porosity, location and regulations must be considered.

Consider filtering the liquid effluent before it reaches the septic field, also known as a French drain.

Today plastic septic tanks are the norm of the modern-day wastewater treatment process.


The Law

Septic tank systems must be designed in accordance with SANS 10400-P, or by a competent person as defined therein, to satisfy the requirements of Part P of the National Building Regulations and Building Standards Act.

  • A person wishing to use the sewage disposal system must make application to the Municipality
  • If granted by the Municipality constitutes an agreement between the Municipality and the customer.
  • The owner is liable for all the prescribed fees until the agreement between the Municipality and the owner terminates.


Speak to Supa Nova to help with planning and creating the right septic system.


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