Unidirectional flushing (UDF) is the most effective way of cleaning water mains and maintaining water quality and system capacity. It also requires the least amount of water of any cleaning method. Valves are closed and hydrants opened to create a one-way flow. This type of high-speed flushing (5 to 6 ft/sec) increases the swiftness of the water in the mains, maximizing shear velocity near the pipe wall. This produces a scouring action that effectively removes sediment deposits and biofilm. Among its many advantages, UDF can help improve water quality by restoring the disinfectant residual, reducing bacterial regrowth, dislodging biofilms, removing sediments and deposits, controlling corrosion, restoring flows and pressures, eliminating taste and odor problems, and reducing disinfectant demand throughout the distribution system. These benefits can also prolong the life expectancy of the system and reduce the potential for waterborne disease outbreaks.

	Conventional flushing in a looped system results in water flowing toward the hydrant from all directions generating lower flow velocity and less scouring of the pipes.		Unidirectional flushing results in water flowing toward the hydrant in only one direction resulting in higher flow velocity, more scouring and better cleaning of the pipes with less water use.

Unique in its class, MWH Soft InfoWater UDF capitalizes on the intelligence and versatility of the GIS geodatabase architecture, in combination with advanced network hydraulic theory. Its advanced capabilities can help water utilities develop effective unidirectional flushing sequences for each flushing zone, quickly identify which fire hydrants and water main valves should be manipulated for proper cleaning while avoiding excessive pressure drops (e.g., below 20 psi) and maintaining the desired level of hydraulic performance in the distribution system. The program also computes minimum flushing time, total flushing volume and pipe length, flushing velocity of every pipe in the sequence, shear stress for every pipe in the sequence, and available flow at the minimum residual pressure. The hydraulic impact of each flushing sequence is also monitored to ensure that the desired minimum pressure is maintained throughout the system. InfoWater UDF generates detailed reports of flushing sequences showing which fire hydrants and water main valves should be manipulated to assure optimal cleaning. Both minimum velocity and minimum shear stress criteria can be specified.

Watch an introduction to Unidirectional Flushing from AWWA. (For more information about this video, visit the AWWA bookstore.)

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InfoWater UDF will help you:

....and many more benefits.