Inflow and Infiltration

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What are Inflow and Infiltration?

Inflow and infiltration or I & I are terms used to describe the ways that groundwater and stormwater enter into the Quakertown Wastewater collection system.  The collection system consists of pipes located in the street or on easements that are designed strictly to transport wastewater from sanitary fixtures inside your house or place of business.  Sanitary fixtures include toilets, sinks, bathtubs, showers and lavatories.

Inflow is stormwater that enters into sanitary sewer systems at points of direct connection to the system. Various sources contribute to the inflow, including footing/foundation drains, roof drains or leaders, downspouts, drains from window wells, outdoor basement stairwells, drains from driveways, groundwater/basement sump pumps, and even streams.

It is illegal to connect these sources to the sanitary sewer system.  They may be direct connections or discharged into sinks or tubs that are directly connected to the sewer system.  An improper connection lets water from sources other than sanitary fixtures and drains to enter the sanitary sewer system.  That water should be entering the stormwater sewer system or allowed to soak into the ground without entering the sanitary sewer system.

These illegal connections can be made in either residential homes or businesses and can contribute a significant amount of water to sanitary sewer systems.  Eight inch sanitary sewer pipes can adequately move the domestic wastewater flow from up to 200 homes, but only eight sump pumps operating at full capacity connected to the sanitary sewer pipe will overload the capacity of the same eight inch sewer pipes.  A single sump pump can contribute over 7,000 gallons of water to sanitary sewer systems in a 24 hour period, the equivalent of the average daily flow from 26 homes.

Infiltration is groundwater that enters sanitary sewer systems through cracks and/or leaks in the sanitary sewer pipes.  Cracks or leaks in sanitary sewer pipes or manholes may be caused by age related deterioration, loose joints, poor design, installation or maintenance errors, damage or root intrusion. Groundwater can enter these cracks or leaks wherever sanitary sewer systems lie beneath water tables or the soil above the sewer systems becomes saturated.

Average sewer pipes are designed to last about 20-50 years, depending on what type of material is used. Often sanitary sewer system pipes along with the lateral pipes attached to households and businesses have gone much longer without inspection or repair and are likely to be cracked or damaged.

The Wastewater Department has an ongoing program of monitoring and eliminating sources of both inflow and infiltration.  This includes sewer main and manhole rehabilitation along with investigating illegal sump pump connections.

It is important for homeowners to know that they are responsible for the maintenance of their lateral. Most homeowners are responsible for that part of the lateral that is from their home to the curb line of the street.  Be aware that problems with your lateral can cause problems within the home.

Inflow and infiltration reduce the ability of the sanitary sewer system and treatment facility to properly transport and treat domestic and industrial wastewater.  As a result of inflow and infiltration, wastewater treatment processes are disrupted and poorly treated wastewater is discharged to the environment.  You can help eliminate these sources of I & I.