A SUMMARY OF FOOTING DRAIN FLOW STUDIES: RESIDENTIAL FOOTING DRAIN FLOWS AND THEIR ROLE AS A SIGNIFICANT CAUSE OF SSOs AND WET WEATHER I/I

Residential footing drains connected to sanitary sewers can be a leading contributor of wet weather inflow; potentially causing basement backups and sanitary sewer overflows (SSOs). The objective of this paper is to summarize data from 15 residential footing drain studies to make conclusions about average footing drain flow peak rates, volumes, and variability, as well as the factors that affect them. The studies reviewed are categorized into two main types. The first type compares per capita sewer flows between areas with and without footing drains (or pre- and post-footing drain disconnection). The second type of study uses direct measurements of footing drain flows, either at the end of a house lead in a manhole, or using a continuous monitor on a sump pump. Findings from these studies have indicated that wet weather flows from areas with footing drains connected to sanitary sewers are 3-4 times higher than in areas without connected footing drains, in some cases accounting for up to 90 percent of the total wet weather infiltration and inflow. Peak footing drain flows vary significantly between houses, but typically range between 2.5 to 10 gpm/house, with some peaks as high as 25 gpm observed. The average dry weather flow found from footing drain areas is 145 to 190 gpd during the summer and spring seasons respectively.