Searching for a universal water loss indicator using correlation and frontier analysis

Ideally, water loss indicators enable tracking water loss levels independent of system specific factors, which allows for comparison between utilities. No universal indicator has been identified, which would be uninfluenced by utility size, network type and other relevant elements. To fill this gap, this study seeks to compare leakage indicators utilising data from 114 Finnish water utilities. Six leakage indicators are examined using correlation analysis and frontier analysis, along with other criteria. In the correlation analysis, the indicators are evaluated based on their correlation with utility specific factors. Instead of actual leakage, non-revenue water is used in the calculations. A new indicator combining non-revenue water per connection and leakage as percentage of system input volume performed best in the analysis. The results indicate that the traditional percentage indicator and non-revenue water per connection may also perform quite well in water loss level comparison between utilities. Comparing the results to previous studies shows that more research is needed to conclude whether a universal indicator could be used for inter-utility comparisons and leakage target setting.