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Flooding & Flood prevention » Sewer Backup

Sewer Backup

Every home in River Forest has a sewer pipe that connects from the home to the municipal sewer which is typically located in the roadway. It is commonly referred to as a “sewer service”. Under normal circumstances, wastewater flows from the home into the municipal sewer and continues to flow (via gravity) through the River Forest sewer network until it flows into a much larger sewer “interceptor” owned by the Metropolitan Water Reclamation District (MWRD). The MWRD is a regional sewer operator that owns a very large sewer network which collects wastewater from all of the municipal sewers in the Chicagoland area and conveys the wastewater to one of the MWRD-owned sewage treatment plants.

See below for:


Potential causes of sewer backup

Cause #1 of sewer backup

The majority of River Forest homes are connected to a “combined” sewer system. This means that the same pipe that carries wastewater through the Village is also tasked with carrying stormwater during rain events. During light to moderate rain events, there is sufficient capacity within the municipal sewer system to carry wastewater and stormwater as intended. However, during heavy rain events the municipal sewer can become overwhelmed and as a result, the water that continues to enter the system may begin to back up. As it backs up throughout the municipal system it can also start to back up through the pipe that connects to your home. If the backup continues to build until it reaches the elevation of a floor drain, shower drain, or other connected drains in your basement, you could begin to see water coming up and out of the drain instead of going down it. This is considered sewer back up. 

Cause #2 of sewer backup

On occasion, the MWRD sewer network can also reach capacity and start to back up. While there are almost no River Forest homes that connect their sewer service directly to a MWRD interceptor sewer, the fact remains that the MWRD interceptors are the receiving system for the entire River Forest sewer network. It is possible that a rain event occurs in a manner that is manageable for the River Forest sewer network but if the receiving system begins to back up, it will back up into the River Forest sewer network and potentially cause sewer back up into homes. For more information about efforts taken by the MWRD to prevent this, click here. There are relief points in the MWRD sewer network known as combined sewer overflows (CSO) in an effort to combat this from occurring, however, this is not always 100% effective. For more information and real time data on CSOs, click here

Cause #3 of sewer backup

While the previously mentioned scenarios do occur, more times than not a sewer back up is caused by a problem located on the sewer service. In this situation, the municipal and MWRD sewer networks may be working just fine, but if the water is unable to get through the sewer service (from the house to the municipal sewer) it can also lead to back up. Causes for this type of problem can include the following:

  • Tree Roots

Sewer service pipes are typically constructed of several pieces of pipe that are joined together at a joint. Over time, trees within the vicinity of a sewer service pipe will send their roots toward the sewer pipe as it can be used as a source of water. While the pipe joints may remain somewhat tight in their connections, very fine tree roots can still work their way into the pipe. While small amounts of tree roots may have little to no effect on the efficiency of the sewer, once the water source is found the tree will continue to send more and more roots toward the pipe and eventually there will be enough roots to cause a substantial blockage. As wastewater from your home is conveyed toward the municipal sewer system, it may become blocked at the tree roots and would then start to back up toward the home.  

  • Sewer collapse

In more established communities such as River Forest, sewer services are often quite old and constructed of clay pipe. While this often has no impact on the efficiency of the sewer service, it does occasionally lead to pipe failures. This can mean anything from a small section of pipe breaking off and falling into the sewer service to entire sections of pipe 2’-3’ long experiencing a collapse. These blockages can be substantial and, if so, may lead to water backing up toward the house. 

  • Back-pitched pipes 

Over time as changes occur in the ground around your sewer service pipe (tree plantings/removal, repeated traffic loading, construction equipment or excavations, etc.) it can cause the ground and potentially portions of the sewer service to settle. When this occurs, the steady slope of the sewer from your home to the municipal system may experience an interruption with a low spot. This low spot can begin to trap and collect debris, which may continue to the point that there is a substantial blockage. Once the blockage is present, it can lead to sewer back up as waste water from the home may not be able to pass through to the municipal sewer system. 

  • Separated connections

The sewer service from your home extends out toward the municipal sewer system in the roadway. The connection between the home’s sewer service and the municipal sewer pipe can often be one of the more fragile portions of the sewer service, depending on the strength of the connection. In some instances, the residential sewer service may settle or separate from the municipal sewer pipe. If this occurs, the flow of wastewater from the house into the municipal sewer network may become partially blocked. Similar to the back-pitched pipes above, even a small blockage can lead to a collection of debris and material that can often lead to a substantial blockage. If the blockage becomes substantial enough, water from the house may begin to back up as it can no longer enter the municipal system efficiently. 


What to do if sewer backup occurs

In the event that you begin to experience sewer back-up, there is unfortunately not too much that can be done to provide immediate relief. While some believe that sewer standpipes can prevent water from spreading throughout a basement, they can also cause substantial amounts of pressure in the sewer service which can lead to additional failures in the pipe. 

Make sure there are no electric wires or devices under the water level and disconnect electrical service to any areas that are underwater. All items that are impacted by flooding from sewer back up should be dried out and cleaned as soon as possible to prevent mold from accumulating. 


How to prevent sewer backup

The following list are measures that can be taken in an effort to prevent sewer back up from occurring:

  • Have your sewer line rodded regularly - this should ensure a clean and efficient pipe from your home to the municipal sewer network. For a list of Sewer and Drain Contractors currently licensed in the Village, click here
  • Once rodded, have a plumber insert a camera into your sewer to “televise” it - this will allow you to see if there is any damage to the pipe and to ensure a clean connection to the municipal sewer network. For a list of Sewer and Drain Contractors currently licensed in the Village, click here
  • Ensure all downspouts and sump pumps are disconnected from your home’s sewer system - if a blockage does occur, the addition of stormwater from downspouts and sump pump discharges can cause significant sewer back up into the home
  • Participate in the Village’s Resident Assistance Program - Protect Your Basement - additional information can be found here.