Gravity sewer

A gravity sewer is a conduit utilizing the energy resulting from a difference in elevation to remove unwanted water.

Sewer systems within comparatively level terrain require careful planning and construction to minimize energy losses in free falls, sharp bends, or turbulent junctions.

Covered sewers are buried below the frost line to avoid freezing, and deep enough to receive gravity flow from anticipated wastewater sources.

[5] The earliest sewers were ditches to remove standing water from muddy locations where dry ground was preferable for human activity.

Combined sewers evolved from the practice of using flow in early drainage ditches to remove other wastes including draft animal feces.

[7] The Industrial Revolution increased population density in manufacturing districts, and produced pipes useful for drain-waste-vent systems from buildings to sewers.