Benefits of Unidirectional Flushing (UDF) Infographic

Benefits of Unidirectional Flushing (UDF) Infographic

Unidirectional flushing (UDF) is a unique process utilized to maintain a distribution system as well as learn critical information about the system. An effective UDF program should be conducted annually, at a minimum. Check out our UDF infographic that shows the benefits of UDF over conventional flushing:


Please feel free to print and share, with attribution, our UDF Infographic. A high resolution pdf can be downloaded by clicking here.

The Criticality of Unidirectional Flushing (UDF) Programs for Water Utilities

water_tap-300x188Water utilities today are faced with a unique set of difficulties. Population growth has resulted in unprecedented demand while climate change has caused supply to dwindle. Increased regulations have forced utilities to invest more and more capital into treatment while budgets have shrunk. In addition, our nation’s aging infrastructure has forced water utilities to heavily invest in repair and replacement of the distribution system. Therefore, it has become critical that utilities utilize the most cost-effective and efficient methodologies in order to maintain and improve their water systems.

A key issue in distribution systems is tuberculation, or build-up, on distribution pipe walls. These deposits, most frequently caused by corrosion and microbial activity, affect both the quality and quantity of the water supply. Excessive tuberculation greatly reduces distribution system efficiency and has a negative impact on water quality. In fact, AWWA has noted that distribution system deficiencies are responsible for over 25 percent of waterborne disease outbreaks in the United States each year.

Silver fire hydrant is spraying water after valve opened with red wrench.

Fortunately, implementation of a planned, systematic Unidirectional Flushing (UDF) Program helps to reduce these issues. UDF is utilized to maintain a distribution system and provides the added benefit of learning critical information about the system. This information allows utilities to efficiently plan and make the most imperative improvements to the system. And while the primary goal of UDF is to clean water mains, there are also several peripheral benefits. A routinely implemented UDF Program helps to regularly exercise hydrants and valves, prolonging the life of the valves and helping to locate any closed or broken valves. Flushing also helps to pinpoint the cause of water quality or pressure issues in a specific area of the system while determining discrepancies between the hydraulic model and the distribution system. Flushing frequently enables system issues to be discovered before they become critical and require emergency service, giving utilities sufficient time to address and budget them.

Manchester-By-The-Sea-UDF-Zone-4-199x300Because demand is highest in summer and would make flushing impractical, and low temperatures in winter would cause unsafe conditions from flushed water freezing on roadways and sidewalks, flushing is typically performed in the spring and fall. Currently, Tata & Howard is assisting the communities of Haverhill and Manchester By The Sea, MA and Norwalk First Taxing District in Norwalk, CT with their annual UDF Programs. Both AWWA and MassDEP recommend that UDF be performed on an annual basis, at a minimum. If a distribution system is too large to perform UDF annually, flushing should instead be scheduled in rotation so that all parts of the distribution system are exercised on a regular basis.

A regularly scheduled UDF Program is one of the simplest and most cost-effective ways of maintaining the health and safety of a water distribution system. For comprehensive information on UDF Programs including case studies, please download our UDF whitepaper instantly here.


Make a New Year’s Resolution to Exercise – Your Hydrants!

resolutions new yearWith the beginning of each new year come all sorts of resolutions – to eat better, spend less, organize the house, and clean the garage. But the most commonly made resolution by far is to exercise to get into better shape. And while we agree with this resolution 100%, it may not be for the reasons you think. You see, we think you DO need to exercise – your fire hydrants!

Hydrant Calisthenics

Exercising hydrants comes in the form of unidirectional flushing (UDF) which, just as the name implies, flushes water in one direction from the cleanest possible source, such as a well, outward to dirty mains, finally exiting a hydrant. This unique process is utilized to maintain a distribution system as well as learn critical information about the system, allowing utilities to make future improvements based on the information acquired. The primary goal of UDF is to clean water mains, removing as much sediment, debris, and loose tuberculation as possible. Performing unidirectional flushing on an annual basis helps to avoid tuberculation and sedimentation buildup. Water mains that are not flushed on a regular, scheduled basis run the risk of building up tuberculation to the point that the buildup cannot be removed by flushing, and this can have a significantly negative impact on water quality, fire flows, and distribution system efficiency.

unidirectional_flushing_programWhile the primary objective of unidirectional flushing is to clean mains, there are also many secondary goals and benefits. Exercising hydrants and valves prolongs the life of the valves while also locating closed or broken valves. In addition, flushing helps to narrow down a search area when trying to determine the cause of water quality or pressure issues in a specific area of the system. In a best case scenario, the flushing will actually alleviate the water quality issues by flushing out any debris or buildup that is causing the problem. Also, there are often discrepancies between the hydraulic model and the distribution system that can be discovered and addressed during flushing. Lastly, flushing helps to determine or disprove suspected system issues. Frequently, these issues are not of an emergency nature and can either be readily corrected during the flushing process or can be scheduled for repair at a convenient time, BEFORE they require critical attention.

According to The American Water Works Association (AWWA), “distribution system deficiencies continue to be responsible for more then 25 percent of waterborne disease outbreaks in the United States each year, a statistic that underscores the need for water suppliers to effectively control water quality within the distribution system. Flushing is one of the most powerful tools available to a water utility for maintaining this control.” For this reason, AWWA has published a set of guidelines to follow when implementing a unidirectional flushing program. They recommend a minimum velocity of 3.0 feet per second, and also recommend that system pressure in the surrounding area maintain 20 psi, similar to the concept of adequate fire flow availability.


happy_new_yearThere is a great deal of information that can be gathered during flushing, and the better the quality of data recorded, the easier it is to compare data, making it easier to determine if changes are occurring or if a problem has developed in the distribution system. Each step of the process is important, and a successful flushing program is a continuous process. The data should be compared on a yearly basis, at a minimum. Gaining five pounds over the course of one year seems insignificant; however, gaining five pounds per year over a course of five years will find a person with his weight up 25 pounds — and that IS significant. The same holds true for distribution systems. If the data is not reviewed annually, small problems have the potential to become large problems, and simple system improvements run the risk of being overlooked.

So while you are making your 2016 resolutions, be sure to include exercise…of your hydrants — your distribution system, customers, and operators will surely thank you. Happy New Year!