- Public Works
- Sewer Information
- Sewer Inflow & Infiltration
- Sewer Inflow & Infiltration Problem
Sewer Inflow & Infiltration Problem
Sanitary sewer systems are designed to carry wastewater from toilets, dishwashers, sinks, or showers in homes or businesses. Inflow and infiltration add clear water to sewer systems increasing the load on the systems. Clear water belongs in stormwater sewers or on the surface of the ground, not in the sanitary sewers.
A stormwater sewer is a pipe system designed to carry rainwater away. Stormwater sewers are normally much larger than sanitary sewer systems because they are designed to carry much larger amounts of water. Drainage ditches also act the same way in many neighborhoods.
When clear water enters sanitary sewer systems, it must be transported and treated like sanitary waste water. During dry weather, the impact of inflow and infiltration can vary from minimal impact to a significant portion of the sewer pipe flow. Wet weather magnifies existing inflow and infiltration sources.
Inflow and infiltration costs water treatment facilities and consumers large amounts of money in water treatment operating expenses. All water entering a water treatment facility must be treated as wastewater causing an increase in operating costs proportional to the amount of clean water entering the sanitary sewer system due to inflow and infiltration.
Costs associated with processing the added clean water from inflow and infiltration are eventually passed back to the consumer in the form of rate increases. By reducing inflow and infiltration, capital and operating costs can be lowered.
Minimizing inflow and infiltration can also increase the lifetime-capacity of a treatment facility and wastewater transportation system. The pumps that are involved with wastewater treatment and transport operate 24 hours a day 7 days a week; however, they must work harder as the sewer system's water level load increases. This puts an unneeded strain on the pumps and shortens the life expectancy of these expensive pumps.
Monitoring the Problem
Once a source of inflow and infiltration has been discovered the city or agency will take appropriate action to resolve the problem, including fixing or replacing damaged or leaky sewer pipes and notifying property owners of improper connections. Periodically the city or agency must monitor and measure their sanitary sewer system to maintain the integrity of the system and determine new sources of inflow and infiltration.
Continuous monitoring is also beneficial to the cities and agencies, so appropriate cost increases can be applied to communities / basins that are heavy contributors to inflow and infiltration into the sanitary sewer system.