Domestic water meter optimal replacement period to minimize water revenue loss

Abstract

Water meter under-registration results in apparent losses and lost revenue for municipalities. Municipalities should scientifically determine the optimal replacement periods for the meters in their particular municipality, as this would result in the formulation and implementation of appropriate meter replacement strategies and a reduction of apparent losses due to water meter inaccuracies. A water meter management database was analysed using the relative meter error method to determine if a relationship exists between domestic water meter age, total registered volume and accuracy, as well as the volume of apparent water losses caused by inaccuracies due to domestic water meter age and total registered volume. The net present value chain (NPVC_n) method was used to determine the optimal domestic water meter replacement period. This study found no relation between water meter age and total registered volume. A relation was found between water meter age and accuracy and well as between total registered volume and accuracy. The median relative meter error was found to decrease with increasing water meter age and to increase from under-registration to over-registration as the total registered volume increased. The study also determined the volume of apparent water losses caused by domestic water meter inaccuracies due to age and total registered volume for this particular municipality to be 1.814 kL∙meter⁻¹∙month⁻¹, which translated to 2.81% of the municipality’s total system input volume. The optimal water meter replacement period of the municipality was determined using the NPVC_n method to be at water meter ages of 9, 12 and 16 years and total registered volumes of 3 971, 5 162 and 6 750 kL at discount rates of 10%, 8% and 6%, respectively. This means that the municipality can now proactively replace its water meters so as to minimize the impact of meter inaccuracies on non-revenue water.

Keywords: water meter age, apparent water losses, relative water meter errors