Applications will be prioritized based upon sewer backup history and location (areas susceptible to sewer backups and flooding.)

This program allows property owners to apply to be reimbursed 75 percent of an installation cost up to $1,500 for a backwater valve.

A sewer backwater valve is a valve designed to allow flow in a sewer lateral in only one direction. The backwater valve allows flow out of the residence through the sewer lateral but will close and block flow coming from the sewer main.

plumbing code

Your sanitary sewer lateral is the pipe that carries your wastewater from your home (toilets, sinks, showers, laundry, floor drains, etc.) to the public sanitary sewer main, which is a larger pipe that is typically under the street.

Typical Floor Drains with backwater valves

Sewer Backwater Valve Benefits

Property owners are responsible for the maintenance, repairs and replacements of sewer pipes on their property. Many Madison area homes are older and lack this protection against backups.

Sewer backups can be expensive to clean up and are a public health and safety hazard.  Sewer backwater valves can help protect homeowners from wastewater flowing back into a home.

Many homes have backwater valves already.  It has become common practice in residential construction to include a backwater valve as part of the floor drain, but it is not required the City or the State plumbing code. Sewer blockages are impossible to predict. While backwater valves are not required for homes, we recommend them for most properties.  A plumber will be able to determine whether you have a functional backwater valve.

Growing Concern for Sewer Backups

Aging Infrastructure

As infrastructure gets older, sewer and water mains become more likely to fail. Failure of water mains, storm sewers, and sanitary sewers may cause more fluid flow into the sanitary sewers, which then may cause backups into sewer pipes into residences.

Climate Impacts

Extreme weather events are becoming  more frequent in the Madison area and may cause more frequent failures in the sewer system.  Properties in low lying areas and properties near bodies of water may be especially susceptible to backups caused by extreme weather events.  Unexpected clogging of sanitary sewer mains caused by buildup of grease, sanitary wipes, and other items in the sanitary sewer system can also results in backups.

Street Reconstruction Project Participation

The Engineering Division piloted the installation of exterior backwater valves as part of designated Public Works street reconstruction projects. Property owners in these designated projects areas are individually contacted to determine if they want to participate.  Their reduced portion of the cost of the installation will be included with their total assessment for the project.

Private Property Participation Eligibility

The program offers participating homeowners a rebate of 75% up to $1,500 to have a backwater preventer installed if it is determined that their property is not currently protected by a functional backwater valve.  The pilot program will also be made available upon request to properties outside of the limits of the above Public Works contracts.  Eligibility for inclusion is limited to 1- and 2- unit residential properties that do not have an existing backflow valve and were constructed more than five years ago.

Interested Participants

  1. Call Us

    Contact City Engineering at 608-266-4751 to answer a few basic questions and confirm you are eligible.

  2. Plumber Visit

    If eligible, City Engineering will set up a time for our plumber to visit your home and do an inspection. The inspection will determine that there is no existing backwater valve as well as identify any clear water connections to the sanitary sewer.

  3. Notice to Proceed

    After your inspection is complete, City Engineering will provide you with a Notice to Proceed Letter.  This letter will tell you if you have any clear water connections that need to be addressed. You can now proceed with obtaining quotes from area plumbers. Work needs to be done by a Wisconsin licensed plumber.


    Property owner will obtain a minimum of three quotes for the work and submit them to City Engineering. City Engineering will reimburse 75 percent of the lowest quote amount up to a maximum reimbursement of $1,500. The maximum reimbursement amount will be provided in writing to the property owner.

  5. 1-Year Completion

    Work shall be completed within one year of the City notifying the property owner of the eligibility for reimbursement. The plumber will need a City of Madison Building Permit.

  6. Submit Form

    Within six months after the work is completed, the property owner shall submit the Sanitary Sewer Backwater Valve Reimbursement Form they were provided, a photo of the backwater valve maintenance sticker in close proximity to the backwater valve or the sewer clean out, and a copy of the paid invoice/proof of payment to City Engineering.

  7. Reimbursement Check

    City Engineering will mail a reimbursement check to the property owner.