Saint John Water conducts an annual unidirectional flushing (UDF) program to clean water distribution pipes. Where our water source is from lakes there is a certain amount of sediment that gets pulled into the system. Old cast iron pipes shed particles too. Flushing uses the power of water to remove silt, sand, and other natural build-up from the inside of water mains.
Unidirectional flushing takes advantage of known scientific principles and control valves to direct water through isolated sections of pipe. The water is flushed in sections –fire hydrant to fire hydrant. The resulting flow moves at an optimum rate of speed, picking up any loose particles and expelling them with the water out of the fire hydrant. Throughout the process water is sampled and tested for clarity (turbidity) to determine when the pipe is clean.
Unidirectional flushing has some distinct advantages. It requires less water to clean a pipe, the flushing typically takes less time, and because valves are used to isolate the section of pipe being cleaned, it limits the number of customers who could be exposed to turbidity (dirty/cloudy water) or lower water pressure. Turbidity is caused by the flushing itself and any particulate it generates. The water is safe to consume.
Saint John Water began unidirectional flushing with a pilot project in 2005. The intention was to grow it into a system wide program and to adopt the method as the standard for routine pipe cleaning. After ten (10) years of development, 2014 marked the fourth year that the Saint John Water distribution system was flushed with the UDF method.
The flushing program is a condition of Saint John Water’s Approval to Operate as issued by the Department of Local Government and Environment.