On-site leakage in selected suburbs of Johannesburg, South Africa

M.Ing.An investigation was conducted on on-site leakage in selected suburbs of Johannesburg to determine the average leakage flow rate of water lost per property, as well as the distribution patterns of leakage flow rates for two categories of properties: Residential (single domestic houses on stands) and Other (non-domestic and large domestic users). The incentive of this research project, funded by the Water Research Commission (WRC) of South Africa, was to provide figures and to gain insight into the magnitude of water lost at the consumer level, also defined as "on-site leakage". Little was published on on-site losses compared to water losses in municipal distribution systems. The key information for this study was collected through physical inspection of a group of randomly selected properties and by means of measurements taken from municipal water meters used for billing purpose. The project was assisted by Johannesburg Water (Pty) Ltd who provided a list of 233 properties having water meters of less than five years old. These properties were chosen at random and included properties whose meters were replaced due to meter failure or customer complaints. The results of the research show that overall 64 % of investigated properties had measurable on-site leakage at an average rate of 22.9 I/h per property, equivalent to a monthly volume loss of 16.5 kl per property. The median rate was 5.7 I/h per property, translated into a volume loss of 4.1 kl/month per property. An analysis of the data revealed that the general extreme value distribution and its derivatives (Frechet, Wakeby, Exponential and Gamma) provide good descriptions of the distribution of on-site leakage rates. The apparent losses resulting from metering errors were also estimated. The results of this study should be of interest to water engineers and to decision-makers involved in water demand management. It could form a basis for further investigation in the analysis of on-site leakage on a large scale in South Africa by systematically monitoring all segregated categories of users throughout different cities and towns in South Africa