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.


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.


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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Water, Water Everywhere: Understanding our Water Infrastructure

Staying afloat of our nation’s growing water infrastructure problems means understanding the culprits

Understanding our water infrastructure

Water main breaks, “Do not drink” orders, and water leak emergencies are headlines we are  used to seeing as across the nation, Americans learn that the country is losing an estimated 2.1 trillion gallons of water each year due to leaking pipes, broken mains, and faulty meters.

The problem is that amongst all the infrastructure systems we have – transportation, telecommunications, air traffic control – water and sewer pipelines are mostly hidden from our daily lives.  We often don’t know there is a problem, until there is one.

And yet, our water system is one of the most important and economically viable infrastructure systems we have in our country. The US Department of Commerce Bureau of Economic Analysis estimates that for every dollar spent on water infrastructure, about $2.62 is generated in the private economy, and for every job added in the water workforce, about 3.68 jobs are added to the national economy.

A recent article from National Public Radio blames much of the problem to aging pipes originally installed close to 100 years ago.   In many cases, however, that isn’t necessarily the case. Some pipes can last hundreds of years in proper soil conditions. In other cases pipes just a couple of decades old can be found in complete disrepair because of the environment around the pipe.

Just think about your town and how it has developed over the last 10,15, or even 20 years.  The town is probably unrecognizable compared to what it looked like 100 years ago when many of the same water lines we use today were installed.  New elements, often corrosive ones, may have been introduced into the soil surrounding the pipelines including landfills, cinders in the pavement, contamination, stray currents, and high groundwater.  These elements represent only a few that will degrade the exterior of the pipe over time, ultimately causing failure.  By understanding why pipes fail and documenting corrosive areas, communities can focus their limited dollars on replacing pipes with a high risk of failure.

It has been estimated that over the next 20 years, upgrading municipal water and wastewater systems is expected to cost between $3 and $5 trillion. Building and replacing water and sewage lines alone will cost some $660 billion to $1.1 trillion over the same time period. This is money utilities will need and that states do not have to give.  With water rates already on the rise, more has to be done to cost efficiently upgrade our infrastructure.

While the country is now faced with the inevitable burden of paying for upgrades, many in the industry argue that there is an efficient way to modernize our water infrastructure without breaking the bank. A suite of cost-effective approaches to reducing water loss and providing smart, responsible water service to customers are now being employed in municipalities across the country. Best practices include state-of-the-art auditing methods, leak detection monitoring, targeted repairs or upgrades, pressure management, and better metering technologies. By adopting such practices, water service providers can save themselves and their communities money in the long run, while protecting water resources and generating economic growth.