page_title: Gravity sewer
section_title: Improved sewer materials
hierarchical_section_title: Gravity sewer / Improved sewer materials
caption_attribution_description: English: This is what lies beneath those manhole covers one sees in the road in Brighton.
context_page_description: A gravity sewer is a conduit utilizing the energy resulting from a difference in elevation to remove unwanted water. The term sewer implies removal of sewage or surface runoff rather than water intended for use; and the term gravity excludes water movement induced through force mains or vacuum sewers. Most sewers are gravity sewers; because gravity offers reliable water movement with no energy costs wherever grades are favorable. Gravity sewers may drain to sumps where pumping is required to either force sewage to a distant location or lift sewage to a higher elevation for entry into another gravity sewer, and lift stations are often required to lift sewage into sewage treatment plants.
context_section_description: The Industrial Revolution increased population density in manufacturing districts, and produced pipes useful for drain-waste-vent systems from buildings to sewers. Gravity sewers have been assembled from cast iron pipe, vitrified clay pipe, precast concrete pipe, asbestos-cement pipe, and plastic pipe. While some older brickwork sewers remain in use, new sewers of diameters exceeding 1 metre (39 in) typically use reinforced concrete. Corrugated metal pipe may be used for storm drains or wastewaters with similarly low risk of corrosive conditions. Non-cylindrical cross-sections may have advantages for large-diameter sewers.
caption: Old brick gravity sewers like this one are typically replaced by reinforced concrete.
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