Causes of Infiltration
Sewer main infiltration is caused by the seepage of groundwater through:
Cracked pipes at times of heavy rain / snow
Causes of Inflow
Sewer main inflow occurs when the addition of groundwater is allowed to discharge into the sewer system, usually because of illegal sump pumping or the opening of manholes for the purpose of drainage.
Infiltration and inflow can cause a system to become surcharged, or overextended, resulting in backups into the home or outside in the street. This is also added cost to the Wastewater Department, as this water will need to be treated as sewage as it passes through the MWRA system.