Methods of Leak Detection: An Overview

In 1957 the AWWA Committee on Revenue-Producing Water presented a report, "Revenue-Producing Versus Unaccounted-For Water," that was intended to aid the water utility industry in evaluating and improving conservation practices [Jour. AWWA, 57:12:1587 (Dec. 1957)]. The eleven members of the committee were managers, superintendents, and engineers from various parts of the country; they represented investorowned as well as publicly owned utilities. The committee agreed that the concept of metered ratio would be the first step in evaluating distribution system performance. [The metered ratio concept was included in the AWWA Annual Survey of Water Utility Operation form, published in jour. AWWA, 62:6:354 (Jun. 1970).] Metered ratio is the ratio of metered sales to metered delivery to the distribution system. Good performance is indicated by a ratio of 85 to 90 percent, when the use of water is between 378 and 472 L (100 and 125 gal) per capita per day. When industrial use causes a higher per capita use, the ratio may approach 100 percent. The difference between the ratio and 100 percent is unaccounted-for water. Factors that affect the ratio are the age of the system and ground conditions; unavoidable leakage; pressures and the source of supply; the quality of materials and workmanship; use per capita per mile of main; the amount of industrial and commercial use; under-registration of domestic meters; and unauthorized use.