An essential part of our system’s maintenance program is to flush hydrants every spring and fall in an effort to clear our water mains of sediment and mineral build-up. This practice improves water quality and helps to extend the life of our water mains.

Water main flushing moves water systematically through sections of our drinking water distribution system, creating a scouring action to clean the line. The increased flow rate scours the water pipe’s inner walls and helps to remove build-up of naturally occurring debris and sediment.

The water is discharged through select hydrants onto local roads or other surface areas. This process is critical to the overall maintenance of a distribution system and is one of the most important practices carried out by public drinking water systems to maintain high water quality, improve the carrying capacity of pipes, and ensure proper operation of distribution system components, such as hydrants and valves.

Spring 2024 Water Main Flushing has concluded, the program will resume in Fall 2024.

Flushing is limited to dead-end water mains only.
Flushing hours are 7:30 am to 3 pm, Monday – Friday, excluding holidays.
Flushing will begin in northwest Sudbury and will travel systematically throughout the distribution system by Section (1-5) ending in the southeast quadrant of town.

View Schedule by Street Name and (estimated) Flushing Date

View Schedule by Flushing Section and Sequence Order

  2024 Spring Water Main Flushing Bulletin

Questions About Flushing? Please contact our Administration office during regular business hours by phone at (978) 443-6602 or email customerservice@sudburywater.com.

Unidirectional flushing (UDF) is a standard industry maintenance practice used to clean, and improve the carrying capacity of water distribution systems. UDF works by flushing the areas closest to the source water (tanks) to the outer edges of the water system. Targeted valves are closed during UDF operations, to minimize disturbances. UDF isolates each pipeline 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. The water is discharged through select fire hydrants onto local roads or other surface areas.

Flushing is conducted Monday-Friday from 7:30 am-3 pm, it is safer for our staff to flush during daylight to work on the streets. Daylight also provides better visibility to see discolored water being flushed out of the system and when water is running clear. Keep in mind the flushing schedule is subject to change based on the progress of the crew, inclement weather, and other water-related emergencies that take precedence over flushing.

There may be a slight drop in pressure or noticeable discoloration of the water from the minerals and sediments that are being flushed out. During the flushing operation in your neighborhood, you will be able to see our crew flushing the water mains through hydrants and ends of water main pipes commonly called blow-offs. The crews will usually direct the water being flushed into appropriate areas to avoid sediment erosion or localized pooling of water, but you may notice water on the street or roadway.

  • Run a cold water tap closest to your meter (usually found in the basement) or a first-floor sink or bathtub faucet for up to 15 minutes, Keep the tap open until the water runs clear.
  • If you have trouble seeing if the water is clear, fill a light or white-colored cup or container to view the water. If the water coming from the tap is not clear after running for 15 minutes, wait 30 minutes and try again.
  • Milky-looking water: Air bubbles caused by opening and closing water main valves, run a cold tap to draw out the air or pockets.
  • Low water pressure: If water pressure or volume seems low after flushing has been completed, check your faucet screens and home filters for trapped particles.
  • Do not run a tap that has a water filter connected to it or the sediment may clog your filter.
  • Avoid running a hot water tap because it could draw sediment into your hot water tank.
  • If you inadvertently drew discolored water into your home while we are flushing your Zone and staining on fabrics and fixtures occurs, rust removal products are available at most home products stores. The District also keeps a steady supply of Iron Out stain remover on hand at our Administration office located at 199 Raymond Road. Iron out packets are free to all District customers, stop by anytime during regular business hours to pick up a few packets to have on hand should staining occur.

It is normal for there to be an increased amount of chlorine in the water during flushing because the velocity of the water is moving through the pipes shortens the travel time from the treatment plant. You can easily remove the chlorine taste and smell by filling an open container with water and keeping it in the fridge for drinking as chlorine will dissipate.

If you are sure that sediment got into your hot water tank, use the clean-out tap at the bottom of the tank to remove any settled material. Follow the instructions which came with the tank to drain the tank and be careful of the hot water.

The hot water should run clear once the cold water is clear.

  • Removes Sediment: Loose sediment and other deposits may slowly build up on the inside of the water mains over time causing discolored water. Flushing at the appropriate velocities can remove these sediments and deposits and will improve taste, odor, and color that may be problematic e.g. naturally occurring iron or manganese deposits in the distribution system may affect the color.
  • Reduces biofilm: Biofilm is a thin layer of microorganisms that can grow on the inside of the distribution piping, A proper scouring velocity must be achieved to effectively minimize biofilm.
  • Maintains Proper Distribution System Operation: Flushing requires the opening and closing of hydrants and valves to ensure that water moves through pipe segments for effective cleaning. This operational practice also provides water operators with the opportunity to identify broken or inoperable valves and hydrants which is important to ensure that they will work properly in an emergency.
  • Improves the Age of the Water in the Distribution System: Flushing can remove water from areas of the distribution system that have low water use. Older water may no longer have the desired chlorine residual.
  • Fire Protection: Flushing allows the assessment of the flow rate available for firefighting purposes.

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 improve water quality by removing mineral sediments, identify broken or inoperable valves and hydrants to assure that they are working at their maximum potential for fire emergencies. In warmer weather disinfectants in the water are consumed more rapidly than in the winter, creating the need to flush even during drought conditions. For these reasons MassDEP allows and encourages flushing during this restriction period in recognition of the value that it provides.

During times of drought, if we start to face high demand periods and our pumps cannot tolerate the additional demand for flushing we may consider delaying routine water main flushing if such delay will not adversely affect water quality. Provided that is not the case, then we plan to continue to flush until the entire system has been addressed for the year. Our goal is to produce the highest quality water at the tap, and flushing is needed for us to meet that goal.

Please contact the District’s Administration office:

8 am – 4 pm Monday, Wednesday, Thursday
8 am – 6 pm Tuesday
8 am – 1 pm Friday



199 Raymond Road
Sudbury, MA 01776