Sewerage System

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Sewer is a system of engineering networks, equipment and facilities intended to remove wastewaters. Unlike the water supply system dedicated to delivering fresh drinking or technical water, the sewerage system handles waste waters – sewage, meltwater, rainwater, industrial water. According to the scale and type of the system, the sewage can be treated, recycled and returned to water basins, or re-used.

The sewerage system should be selected appropriate to the operating conditions, size of the building or a facilities complex, kind of sewage, environment conditions, landscape, availability of surface waters and other case-specific particulars. To make the right choice, look into the classification of sewerage systems.


1. Domestic sewerage systems are intended to serve residential and auxiliary premises. A system covering a single building or a small group of buildings is called local, and a system covering a settlement, centralised.

2. Industrial sewerage systems are intended to treat wastewaters from massive industrial, manufacturing and agricultural sites.

3. Storm water/rain water systems drain the water accumulated through rains and other precipitations from the streets and roofs. Types of storm water/rain water systems:

  • Open sewers with open channels and conduits
  • Enclosed sewers with underground drainage networks and facilities
  • Combined sewers with both open and enclosed elements


1. An indoor sewer is a system located inside a building. It consists of pipelines (risers and horizontal pipes), fittings and other valves, and connected domestic and sanitary appliances (washbasins, sinks, bathtubs, showers, urinals, bidets, toilets).

2. An outdoor sewer is a system beyond a building. It consists of pump plants, pipelines and treatment facilities.

An outdoor sewer can be arranged according to the following principles:

  • Combined system carries all the waste waters by the same pipe
  • Separate (completely separate) sewer carries sanitary sewerage separately from the storm water
  • Semi-separate (incompletely separate) sewer brings all the wastes separately into a common interceptor to combine the flows


Different materials are used for various sections of a sewerage system, as the wastes differ by chemistry and impurities:

  • Metals (cast iron, stainless steel, galvanised steel)
  • Plastics (polyethylene, polypropylene, polyvinyl chloride, fibre-reinforced plastic)
  • Non-polymers (reinforced concrete, asbestos cement, glass, ceramics)


  • Cesspool: a pit or container in the ground, where all the drains are brought to by a sloping pipeline
  • Dry closet: usually, a booth and a tank where wastewater is processed by dedicated biological agents
  • Drainage system brings the wastewater by the drain pipes into a drainage well, where it is filtered and absorbed by the ground
  • Septic tank – a system of several sealed drained chambers, where the wastewater undergoes step-by-step treatment. The outcome may be let into the surface waters or re-used for technical purposes
  • Deep biological treatment plants – complex treatment facilities that combine several special treatment plants

Wastewater disposal methods

Gravity sewer utilises the gravitational operation principle: the wastewater is carried over the pipeline by its own weight.

Pump powered sewer contains pumps to remove wastewaters.