Water Supply
Water supply and wastewater collection systems:
1. A drainage basin (see water purification - sources of drinking water).
2. A raw water collection point (above or below ground) where the water accumulates, such as a lake, a river, or groundwater from an underground aquifer. Raw water may be transferred using uncovered ground-level aqueducts, covered tunnels or underground water pipes to water purification facilities.
3. Water purification facilities. Treated water is transferred using water pipes (usually underground).
4. Water storage facilities such as reservoirs, water tanks, or water towers. Smaller water systems may store the water in cisterns or pressure vessels. Tall buildings may also need to store water locally in pressure vessels in order for the water to reach the upper floors.
5. Additional water pressurizing components such as pumping stations may need to be situated at the outlet of underground or above ground reservoirs or cisterns (if gravity flow is impractical).
6. A pipe network for distribution of water to the consumers (which may be private houses or industrial, commercial or institution establishments) and other usage points (such as fire hydrants).
7. Connections to the sewers (underground pipes, or aboveground ditches in some developing countries) are generally found downstream of the water consumers, but the sewer system is considered to be a separate system, rather than part of the water supply system.
Wastewater Collection Systems:
Wastewater collection systems gather the used water from our homes, businesses and industries and convey it to a wastewater treatment plant. This type of system is also called a sanitary sewer. A similar system known as a storm water collection system conveys water resulting from runoff of rain and snow from buildings and paved and unpaved areas to a natural watercourse or body of water, usually without treatment. This type of system is also known as a storm sewer. In the past, some sanitary sewers and storm sewers were combined into one system. Unfortunately, during heavy rains the wastewater treatment plants served by combined sewers often became hydraulically overloaded and washed out into the receiving stream causing a complete treatment system failure. For this reason, combined sewers are now uncommon.
Types of pipes use in water supply:
Pipes which are commonly used in water supply system are given below.
• Cast Iron (CI) Pipes
• Steel Pipes
• Galvanized Iron (GI) Pipes
• Copper Pipes
• Plastic or Polythene or PVC pipes
• Asbestos Cement (AC) Pipes
• Concrete Pipes
CAST IRON PIPES
These pipes are most commonly used in water distribution system mainly because of the following reasons.
• They are cheaper in cost
• It has high resistance to corrosion
• It is highly durable
C.I. pipes are manufactured by following 4 methods.
• Horizontally cast (MC ware pipes)
• Vertical cast (pit cast in sand moulds)
• Centrifugally cast in sand lines moulds spun type
• Centrifugally cast in water cooled metal moulds
STEEL PIPES
Use of steel pipes in water supply system is suggested when,
• pipes are subjected to very high pressure (i.e. above 7 kg/cm2)
• large diameter pipes are required
Steel pipes are used because they are stronger and lighter in weight as compared to C.I. pipes.
These pipes, however, require adequate preventive measure to sustain adverse atmospheric conditions.
Galvanized Iron (GI) Pipes
This type of pipe is used for water supply work inside the building. These pipes are wrought steel pipes provided with zinc coating.
They are available in light, medium and heavy grades depending on the thickness of the metal. For a 15 mm GI pipe, the thicknesses are 2.0, 2.65 & 3.25 for the light, medium and heavy
grades, respectively. Generally, the medium grade pipes are used for internal plumbing in building.
PLASTIC OR POLYTHENE OR PVC PIPES
These pipes are being used increasingly these days for supply of cold water in external and internal plumbing work.
They are light in weight, non-corrosive, lower in cost and do not require any threading for connections.
There are 3 common types of plastic pipes are available in market, as given below.
• Un plasticized PVC (UPVC) or rigid pipes for use with cold water
• Plasticized PVC pipes which are plasticized with addition of rubber. It has lower strength and lower working temperature than UPVC pipes.
• Chlorinated PVC (CPVC) pipes which can withstand higher temperatures upto 1200 (used to carry hot water)
Classification of sewage and sewer systems:
Sewage is a water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as domestic or municipal wastewater, it is characterized by volume or rate of flow, physical condition, chemical and toxic constituents, and its bacteriologic status (which organisms it contains and in what quantities). It consists mostly of greywater (from sinks, tubs, showers, dishwashers, and clothes washers), Blackwater (the water used to flush toilets, combined with the human waste that it flushes away); soaps and detergents; and toilet paper (less so in regions where bidets are widely used instead of paper). Whether it also contains surface runoff depends on the design of sewer system.
All sewage systems shall be classed as one of the following:
Class 1 – A chemical toilet, an incinerating toilet, a recirculating toilet, a self-contained portable toilet and all forms of privy including a portable privy, an earth pit privy, a pail privy, a privy vault and a composting toilet system.
Class 2 – A class 2 sewage system can only be used for the treatment and disposal of greywater (non-human body waste) i.e., kitchen sink wastes, bathtubs, washing machines, etc… This type of system is ONLY adequate to treat small amounts of greywater (less than 1000 litres per day) for premises such as cottages and hunt camps, etc.
Class 3 – a cesspool.
Class 4 – The most common type of sewage system, which is used to service single-family dwellings, multiple units, and commercial premises is Class 4. It is typically composed of a two-compartment septic tank and a leaching bed. The septic tank collects the raw sewage and helps in settling and digestion.
Class 5 – a system which requires or uses a holding tank for the retention of hauled sewage at the site where it is produced prior to its collection by a hauled sewage system.
Diagram of Trip with water closet:
Drawing for bedding of Sewers:
Drawing for bedding of Sewers:
