Chapter 7 Flashcards
Tests for drainlines
- Alignment test
- Gradient test
- Water test
- Smoke test
- Air test / Pneumatic test
Main usage of water
- Supports lives
- Residential needs
- Fight fire
Conventional sources of water
- Rain
- Groundwater
- Lakes and reservoirs
Non-conventional sources of water
- Atmospheric water generation
- Rainwater harvesting
- Desalination of water
Hard water
Water that is difficult to obtain lather when used with soap
Soft water
Water that easily produces lather when used with soap
Treatment process of water
- Coagulation
- Sedimentation
- Filtration
- Disinfection
- Softening
- Chlorination
Types of drainage system
- Combined
- Separate
- Partially separate
What is separate system and where should it be used
Two set of drains, one for soil and sullage and one for rainwater
Used when rainfall is heavy to withstand the fluctuated flow of water
What is combined system
One set of drain pipes for the soil, sullage and soil water. It is necessary to have only one house connection to the sewer
What is partially separate system
Two set of drain, one set for soil, sullage and some surface water, and one only takes surface water from the road.
Advantages of combined system
- More economical to construct and maintain
- No danger of cross connection of the soil sewer and the surface water sewer
- Occasional flush out for the sewers by storm water keeps sewer clean
Disadvantages of combined system
- Large quantities of sewage received during heavy rain, requires pumping
- Poor self-cleaning velocity
- Difficult to design the size of sewers accurately
Advantages of separate system
- Size of sewers can be accurately determined
- Sewage received at the treatment works is constant with slight variation
- Rainwater can be conveyed to a reservoir for treatment since it is not highly polluted
Disadvantages of separate system
- Costly in constructing and maintaining two set of sewer
- Risk of foul drain being wrongly connected to surface water sewer
Terms used in drainage
- Drain
- Drainline
- Sewer
- Public sewer
- Sewerage
- Sewage
Drain
- Pipes laid underground or on ground surface used for the drainage of one building or buildings adjoining and is within the boundary
Drainline
- Pipes laid underground used for the drainage of one building or buildings adjoining and is within the boundary
Sewer
Drains used by a number of buildings not within the same boundary.
Public sewer
Sewer for which the Local Authority is responsible for its construction and maintenance
Sewerage
System of pipes used for drainage of soil and sullage water of a district and convey them to a suitable point for disposal
Sewage
Foul water such as waste water and soil water
Minimum diameter for branch drainline
Ø100mm
Max distance from inlet of branch drainline to IC
10m
Gradient of branch drainline for Ø100
1 in 20 to 1 in 60
Gradient of branch drainline for Ø150
1 in 30 to 1 in 90
Gradient of branch drainline for Ø225
1 in 40 to 1 in 150
Minimum diameter for main drainline
Ø150mm
Max distance of any main drainline between IC
50m
Gradient of main drainline for Ø100
1 in 30 to 1 in 90
Gradient of main drainline for Ø150
1 in 40 to 1 in 150
Purpose of testing drains
To check for leaks
Location of culvert
- At the bottom of depression where no natural water courses exist
- Where natural stream intersects the road-ways
- At a location required for passing surface drainage carried in side ditches beneath roads and driveway to adjacent property
Types of culvert
- Pipe culvert
- RC Box culvert
- Brick culvert
- Slab and abutment culvert
