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Force mains are typically constructed of welded steel or HDPE jointed to resist pressures within the pipe. Force mains are substantially different from pressure sewers which serve individual properties or groups of properties and provide a means of injecting sewage into a local gravity main.
A sewer pipe is normally at neutral air pressure compared to the surrounding atmosphere.When a column of waste water flows through a pipe, it compresses air ahead of it in the system, creating a positive pressure that must be released so it does not push back on the waste stream and downstream traps, slow drainage, and induce potential clogs.
Pressure sewers enable properties constructed below the nearest gravity main to connect to the local sewerage system avoiding the need for a septic tank or cesspit. [4]In areas where washouts or earthquakes are common, conventional earthenware or cast iron sewerage system may be prone to breakage and leakage.
Cast iron pipe formed using this procedure was typically oven-cooled under controlled time and temperature conditions. As with metal molds, pipe was typically annealed to eliminate any stresses in the pipe, and were then cleaned, inspected, tested, gauged (for dimensions), coated internally and/or externally, and stored for use. [5]
The Hazen–Williams equation is an empirical relationship that relates the flow of water in a pipe with the physical properties of the pipe and the pressure drop caused by friction. It is used in the design of water pipe systems [1] such as fire sprinkler systems, [2] water supply networks, and irrigation systems.
In this domain, the effects of the roughness of the pipe surface must be considered. It is useful to characterize that roughness as the ratio of the roughness height ε to the pipe diameter D, the "relative roughness". Three sub-domains pertain to turbulent flow: In the smooth pipe domain, friction loss is relatively insensitive to roughness.
The term sewer implies removal of sewage or surface runoff rather than water intended for use; [1] 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.
In many countries, PVC pipes account for most pipe materials used in buried municipal applications for drinking water distribution and wastewater mains. [10] Pipe may be made from concrete or ceramic, usually for low-pressure applications such as gravity flow or drainage. Pipes for sewage are still predominantly made from concrete or vitrified ...