Slopes, basements below street level and sewer backups
A home built below the level of the street sewer relies on gravity working against the grade, and a basement bath may use an ejector pump to lift waste upward. If that pump fails or a check valve sticks, the first sign can be wastewater in the lowest room.
Steep lots also mean runoff in heavy rain, which can overload sump pits and add water to the system. Drivers reach Riverdale by the Henry Hudson Parkway, Riverdale Avenue and Broadway, and some hillside streets are narrow, so parking and carrying equipment up slopes should be planned ahead.

