Basics of Plumbing Drainage Principles
Gravity drives waste and water through residential drainpipes. Therefore, the predominant principle of residential drainage systems is that waste runs downhill. Despite their simple guiding principle, drain systems consist of an elaborate arrangement fixtures, fittings, drainpipes and vents. Professionals use the phrase "drain, waste and vent system," or DWV, to describe drain plumbing. Understanding DWV requirements and construction techniques helps you complete plumbing projects or work with contractors. Does this Spark an idea?
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Public or Private Sewer
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Residential drain systems must empty household waste and water into a sewer system. Conventional drain systems direct waste to public sewers or private septic systems. Usually operated by municipal authorities, public sewers are common among urban and suburban neighborhoods. Homes in rural and semi-rural areas usually direct waste into private septic systems. While public sewers typically transport waste to a central treatment facility, private septic systems usually store waste in tanks or pits and slowly leech waste into subsurface soil.
Drain and Waste Piping
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Drain and waste plumbing pipes connect at one end to a sewer or septic hook-ups and at the other end to interior plumbing fixtures, such as sinks, toilets and tubs. Plumbers use both metal and plastic drainpipes to construct drain and waste piping systems. Drain and waste piping gently slopes to direct waste to the main-drain hook-up. Plumbing codes typically require pipes to slope at least 1/4-inch per every foot of horizontal distance, or "run."
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Vent Plumbing
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Constructed from the same metal or plastic drainpipes as drain and waste plumbing, vent plumbing allows air to enter a DWV system. Admitting air to drain piping regulates the system's pressure, which helps gravity-fed drainage and prevents siphonage from plumbing traps. Required for all plumbing fixtures, vent plumbing typically branches from drain and waste pipes and connects to main vent stacks. Vent stacks usually run through wall cavities and protrude from a home's roof.
Plumbing Fixtures
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Drains beneath plumbing fixtures, such as tubs and sinks, consist of traps and drainpipes that connect to main-drain lines. Familiar to most homeowners, plumbing traps are the curved, roughly P-shaped pipes that sit directly below sink fixtures. The curved portion of a trap contains water that prevents sewer gases from wafting into a house. Vent piping prevents trap water from siphoning during flushing or drainage. Traps connect to drain and waste pipes, which empty into main-drain lines.
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References
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