Leak Detection Study
In December 2012, Veritec Consulting was awarded the contract to conduct a leak detection study for the Comox Valley water system. The goal of this study was to find out at a jurisdictional level where the high and low loss areas are. As such, Veritec divided the analysis of the water system into four areas:
the CVRD transmission system
the CVRD distribution system (water local service areas)
the Courtenay distribution system
the Comox distribution system
The leak detection process conducted by VeriTec did not involve on-the-ground leak detection using listening devices or comparable methods. Rather, the approaches used in this study aimed at assigning leakage performance indicators to jurisdictions. Primarily two methods were used:
conducting water audits using the standardized International Water Association (IWA)/American Water Works Association (AWWA) water balance
night flow analysis (Appendices A through D)
Appendix A Night flow analysis [PDF - 4.6 MB]
Appendix B IWA AWWA Standardized water audit 2012 [PDF - 524 KB]
Appendix C Master meter verification [PDF - 1.6 MB]
Appendix D Night flow analysis [PDF - 5.1 MB]
Comox Lake supply leak detection study - water committee presentation - Jul 2014 [PDF - 668 KB]
The water audit method involves analyzing the water coming into the system, compared to what was purchased by the customers, and accounting for all other types of water use, over a whole year. This method was not particularly robust because its accuracy relies on water meter records and not all customers on the Comox Valley water system are metered. This method is still useful however as a benchmark for annual comparison and planning activities.
The more robust/most relied upon method in this case was the night flow analysis. In the middle of the night (2-4am) during the time of year when irrigation is not required, water demand/consumption should be at a minimum. Accordingly, during this time leakage is the biggest proportion of overall flow. Flows measured during this time can form the basis for a snapshot leakage measurement across the system.
The results of the night flow analysis showed that at the time of the test there were no significant water losses found in the CVRD transmission and distribution systems. The infrastructure leakage index (ILI) is an internationally recognized operational benchmark for measuring physical water losses. The ILI which emerged for Comox was 2.6, and for Courtenay 6.3. A general rule of thumb is that an ILI of greater than 3 should be the trigger for greater effort in water loss control. The World Bank Institute has guidelines that provide recommendations for water loss management based on ILI results.
Veritec has provided recommendations for addressing the water loss in both Courtenay and Comox. Action steps for Courtenay include a leakage reduction campaign; assessing leakage components; and assessing scope for pressure management. Action steps for Comox include a detailed assessment of night flow components to ensure the accuracy of the assumptions/estimations, then leak detection if required.
The leak detection study has provided a baseline for the extent of water loss in the Comox Valley water system. The procedures developed during this process will allow future night flow analysis to be conducted on an annual basis, and will continue to provide data for the ongoing water loss management strategy.