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Show A disadvantage of plastic pipe is its susceptibility to fracture as a result of third party diggings, " hot" tapping procedures and differential settlement. Water losses due to fractures can be significant. Pipe Rehabilitation The predominant pipe rehabilitation approaches include cleaning and lining with cement mortar, pigging, slip lining and mortar lining. A pipe that experiences more than two to three breaks per mile per year is often considered structurally unsound and cannot be repaired by cleaning and lining. Unlined cast iron mains can be cleaned and cement lined, thus extending the useful life and postponing replacement. A disadvantage of this process is a reduction in internal diameter of the pipe and a reduced flow capacity. Most utilities replace appurtenances as part of a rehabilitation program. Status Utah currently has no requirements for periodic leak testing of conveyance and distribution systems. Pressure testing of new pipelines is routine as part of the inspection and acceptance process and for qertification of drinking water systems. Several states have enacted legislation to address pipe leak prevention either through specific state codes or through the permitting process. Examples of state regulatory policies are given in Table 4. Typically, in cases where state codes specifically address water losses from water conveyance systems, only general guidelines are given with respect to reduction of water losses from pipe leaks. The reason for the lack of specificity is due to the wide range of pipe maintenance and leak prevention programs practiced. The use of meters to quantify water use and water loss patterns is not universally practiced throughout the U. S. It is, therefore, difficult to determine the amount of water unaccounted- for and to identify vulnerable segments of the water distribution system. Another major problem is the lack of uniformity with respect to installation, calibration, and inspection of water meters. Potential Water Savings From Unaccounted- for Water In order to determine the potential savings from a local leak detection and repair program, the amount of water to be saved must first be estimated. Most Utah water systems meter all water delivered to retail customers. In addition, records are kept of the amount of water purchased or produced. The difference between the amount of water sold and the amount purchased or produced is unaccounted- for water. Unaccounted- for water can fall into several categories: Unmetered Use Most systems in Utah are trying to reduce unmetered water use, especially in cities. The most common unmetered water use is fire fighting and line flushing, but neither of these uses is believed to account for a large quantity of water use. Meter Error Meter error probably causes the biggest difference between volume of water purchased or produced and the volume of water sold. Retail meters generally do not receive the service that the larger wholesale meters receive. When a meter begins to wear and lose accuracy, it will typically read low. If a significant number of retail meters are in need of service the total amount of water sold will be under reported. Reducing or eliminating meter error will not reduce the amount of water used, but it will provide a more accurate determination of the amount of water used. Under reported water use 49 |
