Street trees, attached houses and the line to the street
The blocks around Park Slope are known for mature street trees, and tree roots can find their way into older sewer connections at the joints. Because the houses are attached in rows, a house connection sometimes sits close to a neighbor's, and in some cases lines share a trench or a wall.
That means a repeated backup should not be treated as a simple clog. If clearing the line gives only short relief, the pipe may be cracked, offset or filled with roots. A camera inspection tells you what is really happening before anyone starts digging in the sidewalk.

