The possible cause of persistent nighttime humming noises in areas such as Table View, Parklands and Blouberg has been revealed.

The City of Cape Town has issued an alert clarifying that the mechanical noise reported by some residents could be coming from specialised vacuum and jetting trucks used to clean out wet wells at sewer pump stations.

This comes after dozens of residents reported the humming sounds to Ward 113 Councillor Sue Van Der Linde in recent weeks.

Theories initially included that it could be noise coming from the Astron Refinery, pump stations and the Potsdam water treatment plant, but this was all ruled out. Ship noises, data centres, transformers and Eskom drills at Koeberg were also discounted.

In a post on social media on Wednesday morning, 9 September, the City said the Water and Sanitation Directorate regularly carries out essential wet well cleaning at sewer pump stations.

Wet wells are underground chambers where sewage collects before being pumped onwards through the sewer network.

These cleaning operations require specialised vacuum and jetting trucks, which can generate significant mechanical noise while operating.

The work is generally scheduled between 00:00 and 04:00, when sewer flows into the pump stations are at their lowest.

The City says cleaning the wet wells during this period allows teams to safely access and clean the facilities while minimising the risk of disrupting the operation of the pump station or causing sewer overflows.

“While the City understands that the noise may cause concern or inconvenience to nearby residents, these operations are essential preventative maintenance that helps keep the sewer system functioning reliably and reduces the risk of blockages, equipment failures and sewer overflows.”

The City says it will investigate whether the reported noise is linked to any current Water and Sanitation operations in the area and will continue to make every effort to minimise the impact of essential maintenance work on surrounding communities.