Why is it a requirement to separate your stormwater and sewerage drainage services?

In recent years, The City of Cape Town has implemented a 50-year system whereby they require the separation of the stormwater and sewerage drainage system. This is being implemented through the transfer of ownership of properties, which means that when a property is sold the specific criteria must be ensured before it can be signed off.

There are two main types of water drainage, namely (1) stormwater and (2) sewage. Stormwater is classified as white water that is collected from rain, and does not require treatment. Sewage is classified as black water because of its pollutants and contaminants, which requires treatment before being released or repurposed.

Reasons for the separation of the stormwater from the sewerage drainage:

1) Load control: stormwater entering the sewerage may cause unnecessary flooding of the sewerage services due to increased and unpredictable volumes.
2) Sewage plant efficiency and maintenance control: stormwater entering the sewerage system causes excessive strain on the sewerage treatment plants due to the increased volume.
3) Pollution prevention – within the Cape specifically, stormwater is dispersed into natural water systems such as rivers, dams and the ocean. It is detrimental to these systems if raw sewage is disposed of within.
4) Promotion of natural resources: allowing stormwater to be efficiently reused.