Flow Control - Jan 2012
best practices by Brad Clarke Under Pressure Strategies for Limiting Leakage Loss in Water Distribution Systems W ater is a resource that is often taken for granted Yet as the effects of climate change and population growth take hold the challenges ahead for water supply and availability figure only to increase Consider Adelaide Australia where the Murray River has long supplied the city with its water The Murray River has seen extensive overuse for potable agricultural and industrial use and now due to this overuse and changing weather patterns Adelaide is in trouble In North America Lake Lanier in Georgia essentially the sole source of Atlantas water supply is approaching a critically low period potentially threatening that citys water supply Meanwhile in Las Vegas and the U S Southwest the Colorado River which supplies Lake Mead and the Hoover Dam is in a critical low period as well Unless weather patterns change water supply in these regions will continue to face challenges as population grows and resources dwindle Solutions to Water Scarcity Every water utility has some degree of leakage or water loss within its systems which can be greatly reduced by pressure management In North America for example between 10 percent and 30 percent of the water pumped or fed into the distribution network simply leaks out of the system and into the ground Internationally leakage can be as high as 70 percent Aging infrastructure cracked pipes poorly maintained valves leaking gaskets and leaking threaded connections at curb or corporation stops are only a few examples of In a large city with many millions of residents there may be 100 to 200 pressure zones Each DMA districted metered area will generally provide a payback of six months to one year where leaks or water loss occurs The International Water Association IWA iwahq org and the American Water Works Association AWWA awwa org have many water audit tools that can easily determine the levels of water loss that a water utility might be encountering It is important to keep in mind though the costs of water loss may be far greater than just the cost of the water being lost as energy required to pump this water is wasted chemicals used to treat this water are lost and labor and resources are expended to build additional reservoirs to store more water What is the solution to lost water In an ideal world the solution would be to replace ailing infrastructure entirely old pipes valves and poorly threaded connections to ensure systems dont leak While this would be a very effective solution it is generally not a feasible option due to the high replacement costs it would entail However pro active water utilities will replace a small percentage of challenged systems every year to eliminate or greatly reduce leakage within that particular pipe section This approach is sound and is practiced by many utilities around the world to help mitigate the problem Pressure management is another avenue utilities can pursue to provide an immediate cost effective approach to reduce water loss and leakage Pressure In a System Whats the Big Deal If pressure can be decreased in the system by 1 percent the leakage rate will decrease by 115 percent average and subject to variation In daytime consumers use a lot of water to shower wash cook etc therefore demand of flow increases When this happens pressure is almost always lower At nighttime as demand is reduced the pressure increases in the system It is not uncommon to see pressure change by 15 30 PSI 1 2 Antiquated leaking valve on Catalina Island Calif 16 January 2012 Flow Control
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