Everything You Need to Know About Water Main Flushing

Everything You Need to Know About Water Main Flushing

Chances are that at some point in early spring, you have noticed fire hydrants being flushed and releasing large amounts of water into the streets. While it may appear that hundreds of gallons are going to waste, there are actually several benefits to this hydrant flushing process. Water main flushing is an important preventative maintenance activity that:

  • verifies proper operation of the hydrant
  • evaluates the available flow to the hydrant
  • allows utilities to deliver the highest quality water possible to their customers
  • removes mineral and sediment build up from the water mains
fire hydrant flushing water

Proper Operation of the Hydrant

According to the Massachusetts Department of Environmental Protection (MassDEP), the process of water main flushing is one of the most critical practices carried out by public drinking water systems. This practice allows water operators to identify broken or inoperable valves and hydrants to assure that they are working at their maximum potential.

Fire & Emergency Needs

During the flushing of a hydrant, operators can assess the water pressure and available flow rate for firefighting purposes. It’s imperative that each hydrant is operating as firefighters rely on them for fire-ground operations.

firefighter attaching hose to hydrant

High-Quality Water

Over time, water settles, ages, and is affected by biofilm (a thin layer of microorganisms) that grows on the inside of the distribution piping. Each of these factors affects the quality and taste of the water, so it is important to flush the water out of the mains and hydrants regularly. Flushing can remove water from areas of the distribution system that have low water use, since the older water may no longer have the desired chorine residual.

water coming from faucet

Mineral and Sediment Build Up

Throughout the course of several months or a year, loose sediment and mineral deposits may slowly build up inside of the water mains resulting in discolored water and reduced capacity. Flushing the water mains can remove the sediment and mineral build up, and improve the color, odor and taste of the water if it has been problematic.  Unidirectional flushing at the minimum required velocity will improve the carrying capacity of the mains.

Questions?

Now that we’ve discussed the benefits of flushing our water mains and hydrants, you may have some questions about the process and how it will affect your day-to-day life. We’re here to help!

When will a hydrant near me be flushed?

Hydrant flushing normally takes place at the start of spring. Your Pubic Water Supplier (PWS) should notify you of what streets will be undergoing flushing and when.

What can I do to prepare for flushing?

Prior to local hydrants being flushed, you may want to obtain water (in pitchers prior to flushing) for your everyday use including drinking, cooking, etc.

When the flushing is taking place, water quality may temporarily be reduced. Using water for tasks such as dishwashing, laundry, or showering may result in the discoloration/staining of your clothes or household items. Plan ahead and be sure your laundry and dishes are done before the flushing process begins!

How does water main flushing work?

Water main flushing usually takes place in one of two ways – conventional flushing or unidirectional flushing (UDF). WATER Finance & Management does a good job describing the difference between the two methods. In conventional flushing, hydrants are opened in different targeted areas and discharge water until accumulations are removed and water runs clear. While easy to conduct by water operators and crews, this method requires a lot of water, and may not always clean the pipe completely. With UDF, each pipeline is isolated to create flow in a single direction and quickly clean the pipe. By concentrating the flow, UDF creates higher velocities to clear the pipes and requires less water.

Learn more about the benefits of unidirectional flushing in our infographic here.

UDF-infographic

How will flushing affect my water?

During the process, you might experience a difference in the water pressure in your faucets as well as some discoloration in the water.

How long does it take to flush the hydrant?

Typically, this process takes between 30 and 60 minutes.

When will my water be back to normal?

Once the hydrants in your area have completed their flushing, it won’t be long until your water is ready for normal use again. In most cases, water should run clear with just a few minutes of faucet flow. Turn your faucets on cold and let the water run for 5 minutes or so. If you are still seeing discolored water or sediments in the water, continue running cold water on all your faucets until it is clear. Should your water still be discolored after several hours, please contact your water supplier.

Is water main/hydrant flushing a waste of water?

Although you will see water flowing for up to an hour, rest assured that most of the water that was flushed will return to a river, stream, or aquifer.  Flushing is a necessary process to help keep our water mains clean and clear of sediment, allowing your public water supplier to provide excellent water quality, and increased pressure and flow.

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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:

UDF-infographic

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

Unidirectional Flushing Programs – A Yearly History Lesson Whitepaper

Unidirectional Flushing Programs – A Yearly History Lesson Whitepaper

ABSTRACT: A unidirectional flushing (UDF) program when properly performed can provide a unique chronological account of flow through the distribution system.  While a UDF program cleans the loose debris from individual mains, it also identifies closed and/or malfunctioning valves and provides data relative to pipe friction factors.  Performed year after year, a UDF program can identify the effect of recent system improvements or deterioration through comparison of annual data.

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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.

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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.

Conclusion

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!
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