Uni-directional Flushing (UDF)

Uni-directional Flushing (UDF)

Uni-directional Flushing (UDF) is used to improve operations and enhance the water system. Water main flushing is considered an effective method to remove unwanted tastes, odors, or discolorations of the water, and to improve chlorine residual. UDF, a specific type of water main flushing, uses less water than conventional flushing and provides greater cleaning of the pipes.

UDF isolates each pipeline to create flow in a single direction to quickly and efficiently clean the pipe. By concentrating the flow in one direction, UDF creates higher velocities that are better able to clean the pipe.  The major advantages of this method are improved cleaning of accumulated deposits on pipes, less required water than conventional flushing, and an impact reduction for customers


We started the Water Improvement Project in the spring of 2019 as an effort to clear our water mains of sediment and mineral build-up. This will not only extend the life of our water mains, but it will also improve water quality. 

This project includes Unidirectional Flushing, which involves systematically opening hydrants to “flush” mineral deposits from the pipes; and Ice Pigging, which is done by pumping an ice slurry into the main lines and forcing it along inside in order to scour the interior of the pipe and remove sediment.

We encourage you to subscribe to our website and CodeRed (our emergency notification platform). You will automatically receive updates about the project when your area is being affected.

Current Projects - Updated on 11/1/2021

2021 UDF - Where/When 

  • Contractor, HHydrant Flushing Photoydra Tech, is currently unidirectionally flushing Zone 10 and cleaning and exercising gates in Zone 11. Please visit the Water and Sewer Division's home page for daily News Flash updates on progress.
  • They completed unidirectional flushing of Zone 4, on October 27, 2021.
  • Unidirectional flushing will continue through the fall of 2021, weather permitting, and will also include Zones 9, 11, and 12.

Town-Wide Status

Significant progress has been made since this program began in the fall of 2019. To date, 8 out of the 12 zones in the Town have been unidirectionally flushed. These zones are 1, 2, 3, 4, 5, 6, 7, and 8. Please click on the image below for a map of the flushing zones.

Flushing Program Zone Map
  1. Message from the Water & Sewer Div - Emergency Water Service Repairs are Complete on Main Street

    January 23, 2022, 12:00PM Updated: The Shrewsbury Water Department has completed repairs to a water service break in the vicinity of 448 Main Street. Water service in the area has now been restored. Read on...
  2. Sodium Fluoride for Water Treatment for the Town of Shrewsbury

    Date of Record: 12/8/21 -Due to a global supply chain issue, the inventory of sodium fluoride has been depleted in the Town's water. Dr. Hirsh, Med. Director- Worcester & the Shrewsbury Board of Health are urging parents to fluoride-treat their children. Read on...
  3. Important Message from the Water & Sewer Division - Annual Drinking Water Quality Report

    The annual drinking water quality report for calendar year 2020 is now ready and can be viewed online. This document, also known as the Customer Confidence Report, contains valuable information about our drinking water. Read on...
View All

More Information about Hydrant Flushing