Unidirectional Flushing (UDF)

Unidirectional Flushing is an excellent, water-efficient method of cleaning water distribution pipes, in order to improve water quality and restore capacity. The premise is simple: develop a plan that flushes water from a clean source through a "dirty" pipe and out, working in one direction and one segment at a time. By cutting off other flows, scouring velocities of 5 to 10 feet per second (ft/s) or more are achieved, compared to 1 to 3 ft/s with conventional flushing. At these velocities, UDF scours out sediment, biofilm, corrosion products, and tuberculation. Not only is UDF a more effective way of cleaning than conventional flushing, but other utilities have noted that it uses on average about 40 percent less water than conventional flushing. Equally important, the sediment, corrosion products, and biofilm are flushed out and not just moved to another pipe run – (often the case in conventional flushing). Performed properly, UDF saves significant amounts of water, improves water quality, and pays immense dividends in asset awareness and management for years to come. Data collection is done during the flushing sequences and it will be uploaded to the City’s hydraulic model; it is important to update the flow and pressure data obtained from the sequences as they are being performed.


Signs will be placed at the entrance to the flushing zones a few days prior to flushing. Door hangers will be manually placed in the area a few days before the scheduled flushing. Please see below for flushing areas.


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