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Chapter: Civil : Environmental Engineering : Water Distribution And Supply To Buildings

Water Distribution System Maintenance

Proper maintenance of distribution system components ensures that SPU will be able to deliver reliable water service, reduce the risk of unexpected failures, and provide safe drinking water quality to its customers.




Proper maintenance of distribution system components ensures that SPU will be able to deliver reliable water service, reduce the risk of unexpected failures, and provide safe drinking water quality to its customers. SPU has prepared a number of strategic asset management plans (SAMPs) for each major class of distribution system infrastructure components. The SAMPs outline maintenance strategies for each asset. Summaries of those maintenance strategies are provided below.


Water Mains


Water mains located at 'dead-ends' or with low flows often accumulate sediment or have the potential for microbial growth. SPU crews flush low-flow or dead-end mains to maintain water quality. SPU has also begun a plot unidirectional flushing program, as described in the Chapter


3. Reservoirs and Tanks


Storage facility cleaning is also performed to remove sediment, debris, and/or microbial growth as described in Chapter 3. Water Pump Stations Pump stations in the distribution system are maintained in the same manner as described for the transmission system pump stations, as described in Chapter 4. Water Appurtenances SPU also performs maintenance activities for its valves, hydrants, service lines, and meters to ensure their continuing operation. A brief description of each follows.Valves.  SPU responds to an average of 100 valve-related problems per year. Most valve problems can be categorized as leaks, casting failures, mechanical inoperability, and valves being buried by new pavement. Deterioration of interior packing, broken and bent stems, and construction projects are usually the causes of valve problems. SPU is responsible for operating and exercising distribution line valves. Large valves, those 16 inches or larger, were exercised and inspected by valve crews annually until 2003. Due to shifts in priorities, this routine operation work is performed less frequently. Hydrants. Each fire service agency inspects hydrants located within its service area, generally on an annual basis. Defects are reported to SPU for repair. During a twelve month period in 2002-2003, SPU responded to approximately 2,269 work orders to address fire hydrant defects. During maintenance visits, SPU paints hydrants to prevent exterior corrosion and improve their appearance. The average hydrant painting interval is approximately five years. Service.

 Connections. SPU spends about $1.2 million annually on reactive maintenance and repair of water service lines extending from the water main to a customer's meter. SPU typically learns of water service failures through customer calls. SPU's service connection maintenance program is almost entirely reactive since it is generally not economical to perform preventative maintenance activities on water service lines. The consequences of failure on water service lines are low, and therefore it is more economical to run them to failure.Meters. SPU's retail water meters ensure proper billing of its drinking water sales, as well as wastewater disposal costs. Billing system-generated meter problem reports may be generated under a variety of different conditions: broken meter dials; meters that have been inaccessible for reading for three attempts; consumption that is much higher or lower than what is expected for the customer based on historical information; meter registers that are stuck; and meters that show zero consumption. Customer-reported problems often arise from billing questions. When these problems arise, SPU works with each customer to quickly resolve the issues. Malfunctioning customer meters are much more likely to underregister than over-register. SPU maintains its distribution system water


meters based on meter size and customer type. SPU has a meter testing and maintenance program for its large meters, which represent less than three percent of all retail meters. SPU's


goal is to maintain accuracy of large meters to between 97 and 103 percent as per the guidelines of the American Water Works Association. A large meter with an accuracy falling outside that range is either repaired to restore its performance or replaced.


SPU does not typically perform maintenance activities for small


meters since repairing small meters is not cost-effective and it is


generally cheaper to replace a small meter than repair it.  SPU


replaces about 800 small meters each year.


Record Keeping and Reporting


SPU uses its MAXIMO work management system to capture asset failure, repair, and replacement history. Failure history is not completely reliable because many of the failure codes that were originally developed did not adequately describe the nature of the failure. This problem has since been resolved for all new data entered into the system. SPU uses a geographic information system (GIS) to record and display locations of physical assets and problems. This tool is also utilized to review hydrant spacing and identify hydrants that have deficient spacing.


General, definitions, abbreviations, commonly used waterworks pipes fittings, responsibilities of water and consumers/agents, general principles for installing plumbing works, submissions of pluming proposals, general, submissions, plumbing proposals, format, licensed plumber, commencement of work, interim inspections and final inspections, completion of work, works of a minor nature, metering, general, meterposition, inside service, fresh water supply, flushing supply, fire service, metering requiremnt pipe materials, supply types and arrangements, storage cisterns, water pumps and other miscellaneous, water pumps, valve and taps, earthing, separate metering inexisting premises, authorizing private developers/authorized persons to undertake water supply, connection works, maintenance.


Plumbing installation that receives water supply from the Waterworks has to comply with the Waterworks requirements under the provision of the Waterworks Ordinance/Regulations and Hong Kong Waterworks Standard Requirements for Plumbing Installation in Buildings (HKWSR). Approval from the Water Authority is required in order to construct, install, alter or remove a plumbing installation. Works of a Minor Nature Works of a minor nature are works which can be completed without the involvement of specialized trade skill and those which do not change the general arrangement of the plumbing installation already approved by the Water Authority, or affect the flowconditions of the plumbing system thus causing possible supply problems.


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