Introduction

Johannesburg currently experiences approximately 3500 sewer blockages monthly throughout the 10, 000km of sewer network that it operates and maintains.

The cause of these blockages vary from tree roots in the older established areas, sand infiltration in the lower income areas and general abuse of the network due to improper usage. The sewer overflows resulting from the blockages inevitably result in pollution to the environment and as Johannesburg Water is dedicated to the reduction of environmental pollution a preventative maintenance sewer cleaning program has been implemented.

Operations

Johannesburg Water has a fleet of 9 hydro jetting tankers that are used to proactively clean the sewer network. These tankers range from combination units (i.e. have the ability to jet and vacuum simultaneously) to dedicated jetting tankers.

The tankers operate by using a high pressure water pump, able to generate up to 120 bars of water pressure at a flow rate of 300l/minute. This “jets” water into the sewer and dislodges all accumulated debris that may potentially cause blockages.

Hydro Jetting Vacuum Tanker

The water is pumped through a jetting nozzle, which is thrusted up the sewer line due to the water pressure. It is these jetting nozzles that actually clean the sewers and there are various types available depending on the different cleaning applications, e.g. Cleaning of sand, root cutters, fat removal etc.

Removed Roots

Since the inception of the program, the annual average decrease in sewer blockages in the targeted areas is around 17%. 

The Sewer Service Section, from which these tankers are managed also utilizes 6 CCTV vehicles that assess the condition of sewer pipes and determine the cause of problems that lead to sewer blockages.

Cleared Stone and Sand

These CCTV teams are vital in determining the condition assessment of the sewers as they allow the operators to look inside the pipes to physically see the problems.

In addition to the above mentioned jetting program, a manual depot based sewer cleaning program is also in place, This program uses manual rodding methods to preventative sewer cleaning.

The Sewer Services Section also has 4 dedicated teams that routinely patrol the large diameter outfall sewers that are usually located in more remote areas, The Outfall Sewers are checked and basic maintenance is done on these sewers by the 4 teams.

It is anticipated that by using the above mentioned equipment, that JW can reduce the annual sewer overflows that are caused due to maintenance problems.