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Private Property Infiltration & Inflow Reduction

Program Overview

The goal of the Private Property Infiltration and Inflow (PPII) Reduction Program is to reduce the risk of basement backup events, by reducing the amount of clear water that enters the sanitary sewer system through private property infiltration and inflow points.

The program is being funded through a grant provided by the Milwaukee Metropolitan Sewerage District's (MMSD) Private Property Infiltration & Inflow Reduction Program. 

This program involves DPW working within neighborhoods that have been identified as having high rates of clearwater infiltration and inflow. Past projects typically consisted of Sanitary Sewer Lateral Rehabilitation and Foundation Drain Disconnection. These projects are administered by DPW at no cost to residents. Though participation is voluntary, the more homes that participate, the stronger the impact this program will have on lowering costs and reducing basement backups. Residents can learn about the PPII investigations through this visual process guide or the YouTube video below, both created by Michael Timm and Kelly VanZant.

Currently, DPW is administering a pilot PPII project in the Grasslyn Manor neighborhood. Learn more about the project on its EngageMKE project page.

In addition to the PPII program, DPW works to get ahead of sewer problems by inspecting sewers regularly, and conducting sewer relays and cured-in-place lining projects. 

Sewer Projects    Grasslyn Manor Project Page

Milwaukee Sewer Systems 101 

The City is served by two different sewer systems. 

  1. Combined Sewer System – Sanitary sewage and stormwater are conveyed through a single pipe. A majority of the peak flow experienced in the system is due to stormwater runoff and groundwater infiltration. All flow is sent to the wastewater treatment plant.
  2. Separate Sewer System – Sanitary sewage and stormwater are conveyed separately in two pipes. 
    • The sanitary sewer in the separate system is design to carry base sanitary flow only, so increase in flow due to Infiltration or Inflow can cause the system to surcharge, increasing the risk of basement backups. 
    • Additionally, extra water that enters the sanitary sewer through Infiltration and Inflow is sent to the wastewater treatment plants, where it must be processed. This negatively impacts the performance efficiency of the treatment plant, resulting in higher costs for users. 
    • The storm sewer in the separate system collects stormwater runoff and groundwater infiltration and carries it directly to a local waterway and, ultimately, Lake Michigan.

Sewer Diagram

Past PPII projects typically consisted of two different projects: Sanitary Sewer Lateral Rehabilitation Project and Foundation Drain Disconnection Project. Details on each below. 

  • Sanitary Sewer Lateral Rehabilitation Project
  • Foundation Drain Disconnection Project

This portion of the program removes the sources of infiltration caused by faulty sanitary sewer laterals by rehabilitating a home’s lateral. 

  1. Sanitary sewer lateral is inspected. 
  2. Cured-in-place pipe (CIPP) technology is used to insert a flexible liner into the existing pipe. 
  3. This liner is inflated inside the pipe, and then cures to a hard state. 
  4. The final product is a seamless, jointless, structural pipe.

BEFORE                                                                                                                                                

Lateral has various defects. Clear water can enter the lateral through Infiltration points.                            

Sanitary Sewer Lateral - Before                                                                         

AFTER

Lateral is smooth and sealed. Clear water cannot enter the lateral. 

Sanitary Sewer Lateral - After

Most homes built after 1920 have foundation drains that surround the home. These drains collect the ground water that gathers at the home's foundation, and drains the water away from the home.

Many homes in the City of Milwaukee that were built prior to 1954, had their foundation drains directly connected into the sanitary sewer system, rather than being collected by sump pump system and discharged into a storm sewer or into the home's yard. 

Foundation drain connections contribute a considerable amount of inflow into the sanitary sewer system. This portion of the program removes that source of inflow by disconnecting foundation drains from the sanitary sewer system, and rerouting the drains into a newly installed sump pump system.