Basement Drain Backflow Preventer Program

Do you have a drain in your basement floor?

A simple device in your sewer line, if properly maintained, can prevent wastewater from backing up into your basement. A one-way valve is installed in your line to allow wastewater to flow out, but it swings shut when wastewater tries to flow back in. The City of Chelsea Public Works Department has a program that may assist homeowners with the cost of installing backwater devices on their sewer lines. Backwater devices are designed to prevent wastewater from backing up into the sewer service line and into basements from the main trunk line.


Most of the time, the City of Chelsea’s combined sewer and drain pipes have adequate capacity to carry wastewater to the treatment plant. But during heavy, extended raining periods when the ground water is high, the capacity of some sections of the sewer system is exceeded. To make matters worse ground water or surface water may enter older sewer pipes through cracks and, added to the wastewater flow, will exceed the space available in the pipe. When these conditions occur the water has to go somewhere. If it can't flow down the main pipe, it will back up into the service line and, possibly, all the way into the basement. Basement drains like the one pictured below not only let ground water out but also allow sewerage to flow into your basement during heavy rains.

How does the sewer service backflow preventer program work?

  1. City will reimburse homeowners up to $2,500 for this work. 
  2. Properties eligible are owner-occupied 1, 2 and 3 families and condos.
  3. Non-profits may be eligible at discretion of the City.
  4. To be eligible, City must confirm that the property is subject to repeated sewer backups during storm events.  Homeowners must complete, at its own expense, televising of sewer service lines to ensure sewer connection is not compromised.
  5. Owner responsible for obtaining own plumber for work.  Work must be completed and inspected by ISD before any reimbursement is processed.
  6. Owner must provide proof of Invoice reflecting cost.  The maximum reimbursement is $2,500.
  7. Owner must sign both Agreements drafted by Law Department (which includes the statement that City makes no admission of liability) and W-9 form for tax purposes. The agreement shall include an attachment prepared by DPW that explains how a sewer service backflow preventer operates. This will include an explanation of maintenance requirements and operational limitations on building sewer service during events where the device is activated.
  8. Owner must also agree to future inspections of the device by ISD or DPW, at the City’s discretion.
The backwater prevention device belongs to you, and you are responsible for continued maintenance and repair. Ask your plumbing contractor for maintenance instructions. 

Download the application package:
1.Basement Drain Backflow Preventer Application (PDF)
2. Basement Drains Information (PDF)

For more information
Contact Chelsea WSD to find out more about the program or contact Christopher Barrett, DPW Deputy Commissioner, at 617-466-4212.