Education on Inflow and Infiltration

While watching TV last night, I noticed a home improvement show that was remodeling a wet basement in a town in New Hampshire. In the process of remodeling, they used a sealant on the outside of the basement. They had excavated down to the footer and were laying a new sewer line to the street. At the corner of the house, they tied the foundation drain and gutter downspouts into the new sewer line. This is a classic case of outdated practices and lack of education on sewer lines.

Now you may wonder, what is wrong with this process? In most forward thinking cities, there are sewer-use ordinances that make it illegal to tap into the sewer system or inflow. An individual who uses practices as described above or has foundation drains, roof drains or a sump pump attached to the sewer system is in violation of the ordinances in their cities.

We don’t think too much about a sump pump that runs continuously to keep the water under control in the basement on a rainy day. If it is a 25-gallon-per-minute pump, it will pump 36,000 gallons per day (GPD) into the collection system. Therefore, ten houses produce 360,000 GPD. Now consider how many basements with sump pumps exist in your town.

Consider this: a 1,500-square-foot home with gutter downspouts attached to the sewer system adds approximately 930 gallons to the system per inch of rain. If there are 100 homes attached to the sewer, approximately 93,000 gallons are added per inch of rain. Then add all of the other houses, schools, businesses and churches in the city to that equation and you accumulate a lot of extra water going into the sewers. Additionally, all the water collected in the sanitary sewer system has to be treated as sanitary waste at a fairly high cost per gallon. Therefore, if we can keep unnecessary water from entering the collection system, then we can continue to keep the price for service low and not be required to build a new wastewater treatment plant to handle the increase in flow.

Another problem caused by this type of illegal tap is sanitary sewer overflow from manholes and lift stations that can’t keep up with the increases in flow caused by inflow and infiltration. These overflows increase the pollution to our streams and spread bacterial contamination.

Most people in your service area don’t realize that these types of flows are a problem. As operators, we need to educate the public on the way things should be done and highlight any remedial measures that can be taken to combat the growing I and I problem.

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