Sewer appurtenances and their necessity

Definition

Sewer appurtenances are the structures and accessories built along a sewerage system, apart from the sewer pipes themselves, that help it work properly and make it easy to inspect, clean, ventilate and maintain.

Need (necessity) of sewer appurtenances

Sewers are underground, closed conduits. Without appurtenances it would be impossible to operate them safely. They are needed:

1. To inspect and clean the sewers and remove blockages.
2. To admit storm water and surface runoff (street inlets) in combined and storm systems.
3. To change direction, gradient or size of sewers and join several sewers (manholes).
4. To reduce velocity and deliver at the lower level on steep grounds (drop manholes).
5. To keep the sewer self-cleansing in flat areas through flushing devices.
6. To keep out harmful materials: catch basins retain grit and silt, and grease traps retain oil and grease which would block sewers.
7. To ventilate the sewers and prevent accumulation of explosive and poisonous gases (ventilating shafts).
8. To cross obstacles such as rivers and depressions (inverted siphons).
9. To discharge sewage safely to the receiving water (outfalls/outlets).

Examples and their function