Without an air gap, lines to underground sump pump discharges could freeze or get clogged. Photo: RJN Group Inc.
Typical configuration for a storm sump connected to the sanitary sewer with a diverter valve. Drawing: RJN Group Inc.
Dye test to confirm the location of a sump pump's discharge point (here, it's the larger white PVC with metallic hanging strap). To identify a footing tile, auger drill along the foundation while dye testing or inspect the service lateral from the cleanout or main sewer with a launcher camera. Both methods can produce a false positive, but they're much more reliable than smoke testing. Photo: RJN Group Inc.