Greenfield PPII Program

PPII Program (Private Property Inflow / Infiltration)

The Greenfield PPII program is a collaborative effort between the City of Greenfield, the Milwaukee Metropolitan Sewerage District (MMSD) and private property owners. The goal of the program is to work with private property owners in an effort to identify the source of, and reduce the inflow and infiltration of stormwater and groundwater from entering the sanitary sewer system. MMSD has provided grant funding to Greenfield and other municipalities in our region to help begin to address this issue.

Sewer Systems

The City has two separate sewer systems. Sanitary sewer and storm sewer.

The sanitary sewer is a system of underground pipes that carries sewage, or waste water from bathrooms, sinks, and kitchens to the MMSD wastewater treatment plant for treatment prior to returning it to Lake Michigan. 

The storm sewer is a system designed to carry stormwater (rainfall and melted snow), from storm inlets, ditches and roads, untreated into local streams, rivers, and lakes.

The Problem

Sanitary sewer systems are designed to carry a daily volume of waste water flow.  In large rain events or wet weather conditions where stormwater and groundwater are allowed to enter the sanitary sewer system, the volume of flow in the sanitary sewer system can increase greatly as stormwater and groundwater become mixed with the normal daily volume of waste water flow.  In some cases, the change in volumes of flow from dry weather to wet weather in the sanitary sewer system can be significant depending on groundwater depths, the number of connections to the sanitary sewer, the amount of rainfall, and the flow characteristics of the sanitary sewer pipe.

When a large increase in the volume of flow occurs, the volume of the flow into the sanitary sewer system can over exceed the capacity of the system leading to basement sewage backups, sanitary sewer overflows into local waterways and additional sewage treatment costs.

Stormwater and Groundwater Sources

Stormwater and groundwater can enter the sanitary sewer system from many different private property sources.  Some of the more common sources include:

  • defects in private sanitary sewer laterals such as defective pipe, root intrusions, separated or misaligned pipe joints, faulty pipe to pipe connections, etc.
  • direct foundation drain connections of drain tile to sanitary sewer through a palmer valve
  • direct downspout connections into the sanitary sewer system
  • broken clean-out covers on sanitary sewer laterals
  • illegal plumbing in basements (i.e. sump pump discharging into stationary tub)

Questions or Comments?

PPII house schematic


Building foundation drains, downspouts, and other types of basement piping, if connected to the sanitary sewer system can channel stormwater and groundwater directly to the sanitary sewer system.  This process is called inflow. 


Over time, a sanitary lateral can develop cracks and separations at joints causing stormwater and groundwater to leak or infiltrate into the pipe.  This process is called “infiltration.”

Foundation Drain Connections

Until 1954, it was legal to build a home with the foundation drains connected directly to the sanitary sewer system.  Many of these types of connections are still in existence today and are not considered illegal, but can contribute a significant amount of groundwater flow into the sanitary sewer system on a daily basis.  When asked, we recommend that these connections be disconnected, however residents are not required to separate these connections at this time.

After 1954, it became illegal for new foundation drain connections to connect to the sanitary sewer system.  Homes built since 1954 should have sump pump systems that collect water from the foundation drain system and discharge that water to the lawn or storm sewer system thereby keeping it out of the sanitary sewer system.

For those homes that still have their foundation drain connected directly to the sanitary sewer system, this connection most often takes place under the basement floor and near the basement floor drain through a plumbing device called a palmer valve.   

Palmer Valve

A palmer valve is a type of check valve that was designed to allow the groundwater that collects in the drain tile from around your foundation to be directed into the sanitary sewer system through a flap that would open as water flow or pressure increased behind it. 

Since palmer valves were made of metal, over time the ‘flap’ tended to rust or become frozen and inoperable.  Once the flap was inoperable, foundation drainage could not discharge freely into the sanitary sewer and the foundation drain tile system had nowhere for the ground water to drain to.  In many cases, this led to increased hydraulic pressure on the basement floor and foundation wall and common basement issues such as cracks in the floor and walls, basement seepage, etc.

Sump Pump System

Once a foundation drain connection to the sanitary sewer lateral or the palmer valve is disconnected, a sump pump system should be installed so that the groundwater near the building foundation has a place to drain to.  Groundwater is directed to the sump pump system where it is pumped up and away from the foundation either to the storm sewer system, or to surface grade around the structure.

What Can Be Done To Help?

In order to work to eliminate the sudden change in the volume of flow in the sanitary sewer system, efforts need to be made to try and keep unwanted stormwater and groundwater from entering the sanitary sewer system.

While efforts have been made by Greenfield and many other municipalities over the last several years to greatly reduce inflow and infiltration in our “public” sanitary systems through pipe lining, manhole repairs and other rehabilitation efforts, there remain issues with inflow and infiltration from the “private property” side of the sanitary system.

The "public" side of the system typically includes the main pipes and maholes in the roadway, while the "private" side typically includes your building’s plumbing, including the lateral from the building that connects to the "public" sewer main.

MMSD has started to provide grant funding to Greenfield and other municipalities in our region to help begin to address the inflow and infiltration on the private property side.

While it would be impossible to eliminate all stormwater and groundwater from entering the sanitary sewer system, our goal is to try and reduce as much stormwater and groundwater from entering the sanitary sewer system from the private property side of the system as we possibly can.

I Don’t Have Problems With Sewer Backups.  Why Should I Participate in PPII Reduction?

Even if you are not experiencing backips or issues with your private plumbing system, you may still be contributing to the overall problem and may not realize how big an impact your foundation drain connection or leaks in your lateral may have.  A leaky lateral can contribute on average as much as 40 or 50 gallons of water per minute to the sanitary sewer system.  Foundation drain connections and other illegal connections to the sanitary system may also be contributing an equal amount, or more.

PPII Inspection Processes

The first step in identifying potential PPII related defects is to conduct an inspection at your property.  A typical PPII inspection is likely to include the following:

  • An inspection of the property exterior to review property grades, downspout discharge locations, sump pump discharge, etc.
  • An inspection inside your basement in order to evaluate house plumbing configurations, the status of a sump pump system (if any), the status of foundation drain connections and/or palmer valve, etc.
  • Televising your sanitary sewer lateral in conjunction with dyewater injections into the ground above the lateral and into gutters and downspouts to look for clear water entering your lateral.  To access your lateral, we typically look to use your basement clean-out as the access point.
  • During the inspection, the City would document our findings by taking photos, making sketches, capturing sanitary lateral televising footage, etc.
  • On average, each inspection is likely to take between 30 minutes to one (1) hour to complete and someone would need to be home.

PPII Rehabilitation

Depending on our findings during the investigative phase, your property may or may not be a candidate for a PPII construction rehabilitation phase.  Typical PPII rehabilitation work includes capping palmer valves, sump pump installation, gutter and downspout disconnections, and sanitary sewer lateral rehabilitation.

MMSD Pipe Check Program

Learn more about MMSD's Pipe Check Program here.

In collaboration with MMSD


PPII Videos & Images

  1. PPII Videos
  2. PPII Images