2006 Water Comprehensive Plan - City of Bellevue

• Apparent Losses: Includes unauthorized uses and customer meter inaccuracies,both of which are lost revenue opportunities.• Real Losses: Includes various types of system leaks. A certain level of leaks isunavoidable, however, leaks beyond that level should be fixed in order to not undulyburden both the natural resource and the physical infrastructure.• Remainder: This is not part of the IWA’s official water balance format. Under theIWA’s protocol, any amount that can not be assigned to another category is put intothe leaks category. For this Water Comprehensive Plan, any amount that could notbe assigned to another category was put into the Remainder category, toacknowledge that data systems are not currently set up to track all of thesubcategories discussed above.The third level simply further splits water into additional sub-categories.Water Loss AnalysisIn 2003, Bellevue developed a “Water System Loss Report”, which summarized analysis ofunaccounted for water conducted between 2001-2003 to better understand and quantify itsvarious components. The report included analysis of five areas:• Distribution system losses• Inlet meter discrepancies• Customer meter inaccuracies• Billing adjustments• Miscellaneous other uses (e.g. maintenance, construction, fire-fighting)Bellevue’s analysis concluded that between 1998 and 2000, its non revenue water duringthat period was comprised as follows:10% System leaks35% Inlet meter inaccuracies45% Customer meter inaccuracies10% Miscellaneous other100% Total non revenue waterLeak Detection Survey: In 2001, Bellevue retained Utility Services Associates to conductwater line leak detections surveys on a representative portion of the distribution system.Again, the water lost to leaks was estimated at approximately 1.0%, or 60 million gallons peryear. The survey covered approximately 45 miles (or 8%) of the distribution systemrepresenting various material types, geographic locations, soil conditions, and pipecharacteristics such as size and age. Leakage was generally caused by minor system leaksfrom pipes and appurtenances, including hydrant foot valves. The report recommendedperiodic leak detection surveys on representative samples of the water system, as a costeffectivetool to avoid escalation of water loss due to system leaks.4-5