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Countywide Inflow and Infiltration Elimination Program

Because of continuing problems with overloaded sanitary sewers, MSD is inspecting the sewer system in your neighborhood.   This inspection will reveal the primary sources of inflow and infiltration that are causing the problems.

What are inflow and infiltration?

Inflow and infiltration are terms used to describe the ways that groundwater and stormwater enter the sanitary sewer system.

Inflow is water that is dumped into the sewer system through improper connections, such as downspouts and groundwater sump pumps.  (Sump pumps that pump only laundry water or other sanitary wastes are not a problem.)

Infiltration is groundwater that enters the sewer system through leaks in the pipe.

All of this water is called "clear water" (although it may be dirty) to distinguish it from sanitary sewage.

Why is this water a problem?

Clear water belongs in storm sewers or on the surface of the ground, and not in the sanitary sewers.  When clear water gets into the sanitary sewers, it must be moved and treated like sanitary waste.  Too much clear water often causes sewer backups and overflows when it rains.

What is a sanitary sewer?

A sanitary sewer is a pipe located in the street or easement that is designed solely to transport wastewater from sanitary fixtures inside your house or place of business.  Sanitary fixtures include toilets, sinks, bathtubs, showers and lavatories.

What is a storm sewer?

A storm sewer is a pipe designed to carry rainwater away.  Storm sewers are normally much larger than sanitary sewers because they are designed to carry much larger amounts of water.  Drainage ditches and swales perform the same function in many neighborhoods.

What is an improper connection to the sanitary sewer system?

An improper connection permits water from sources other than sanitary fixtures and floor drains to enter the sanitary sewer system.  That water should be going to the storm sewer or allowed to soak into the ground without entering the sanitary sewer.

What are different types of improper sanitary sewer connections?

Some examples of improper connections include downspouts, groundwater sump pumps, foundation drains, drains from window wells and outdoor basement stairwells and drains from driveways.

Where should the water from downspouts, groundwater sump pumps, and/or other clear water sources be directed?

MSD's Wastewater / Stormwater Discharge Regulations and the Kentucky State Plumbing Code require this water to be diverted to storm sewers or above-ground drainage ditches.

Why is it important for everyone to remove improper connections?

Removing improper connections will significantly reduce the flow of clear water to the sanitary sewer system.  This will reduce the possibility of basement flooding due to overloaded sanitary sewers and lessen the amount of water that has to be treated.

How can overloaded sanitary sewers cause basement flooding?

The water in an overloaded sewer flows at a higher level than normal.  If the home has sanitary fixtures or floor drains that are below this higher, overload level, water can flow backward through the sanitary sewer lines into the basement.

Do improper connections really contribute large amounts of clear water to the sanitary sewer system?

Yes, and here's why: An eight-inch sanitary sewer can handle domestic wastewater flow from up to 200 homes, but only eight sump pumps, operating at full capacity, or six homes with downspouts connected to the sewers, will overload this same eight-inch line.

Inflow and Infiltration continued

For more information, please contact:  Angela Akridge

Last Updated: February 28, 2012

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