Unidirectional Flushing (UDF) - Updated on May 23, 2023

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. One complete unidirectional flushing of all 12 Zones was completed in December 2021

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 5/20/2022

2022 UDF - Where/When 

  • Contractor, Hydra Tech, has completed unidirectional flushing zones 2 and 5. Flushing is completed for the season. Please check our Water and Sewer NewsFlash for the most up to date information. 

Town-Wide Status

The unidirectional flushing program began in the fall of 2019 and one full cycle of flushing all of the zones was completed in 2021. Please click on the image below for a map of the flushing zones.

Flushing Program Zone Map
  1. Important Message from the Water and Sewer Division - Unidirectional Flushing on 12/11/2023

    On Monday, December 11th, the Shrewsbury Water Division will be conducting unidirectional flushing in the Barnard Rd, Rawson Hill Dr, Deerfield Rd, Tanglewood Dr, Forest Hill Dr, Ashwood Cir Hemlock Cir, Balsam Cir and Birch Brush Rd neighborhood. Read on...
  2. Important Message from the Water & Sewer Division - Water Service Interruption on Saturday 12/9/2023

    On Saturday December 9, 2023, the Shrewsbury Water Department will be conducting an emergency water service repair near the Coolidge School on Florence Street. Read on...
  3. Important Message from the Water & Sewer Division - Annual Drinking Water Quality Report for 2022

    The annual drinking water quality report for calendar year 2022 is now ready and can be viewed at www.shrewsburyma.gov/depreportccr This document, also known as the Customer Confidence Report, contains valuable information about our drinking water. Read on...
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More Information about Hydrant Flushing