# Civil Engineering Drawing Questions and Answers – Schedule of Rates for Water Supply works

This set of Civil Engineering Drawing Problems focuses on “Schedule of Rates for Water Supply works”.

1. As per IS: 1172-1963, water required per head per day for average domestic purposes, is?
a) 120 litres
b) 135 litres
c) 75 litres
d) 195 litres

Explanation: For domestic purposes – 135 litres to 225 litres,
For industrial purposes – 50 litres to 450 litres.

2. Turbidity of raw water is a measure of _____________
a) Suspended solids
b) Acidity of water
c) B.O.D
d) Repair Work

Explanation: The definition of Turbidity is the cloudiness or haziness of a fluid caused by suspended solids that are usually invisible to the naked eye. The measurement of Turbidity is an important test when trying to determine the quality of water. It is an aggregate optical property of the water and does not identify individual substances; it just says something is there.

3. Which among the following quantity is considered while estimating the sewage quantity?
a) Addition due to unaccounted private water supplies
c) Subtraction due to water losses
d) Addition due to unaccounted private water supplies, infiltration and water losses

Explanation: Addition due to infiltration-This is additional quantity due to groundwater seepage in to sewers through faulty joints or cracks formed in the pipes. The quantity of the water depends upon the height of the water table above the sewer invert level.
Addition due to unaccounted private water supplies- People using water supply from private wells, tube wells, etc. contribute to the wastewater generation more than the water supplied by municipal authority. Similarly, certain industries utilize their own source of water.
Subtraction due to water losses -The water loss, through leakage in water distribution system and house connections, does not reach consumers and hence, not appear as sewage.

4. The future period for which the provision is made in designing the capacities of the various components of the sewerage scheme is known as the ______________
a) Design period
b) Manufacture time
c) Construction work
d) Repair work

Explanation: The design period depends upon the following:
-Ease and difficulty in expansion,
-Amount and availability of investment,
-Anticipated rate of population growth, including shifts in communities, industries and
commercial investments,
-Hydraulic constraints of the systems designed, and
-Life of the material and equipment.

5. A city has a projected population of 60,000 spread over area of 50 hectare. Find the design discharge for the separate sewer line by assuming rate of water supply of 250 LPCD and out of this total supply only 75 % reaches in sewer as wastewater. Make necessary assumption whenever necessary.
a) 0.26 m3/s
b) 0.6 m3/s
c) 0.76 m3/s
d) 3.26 m3/s

Explanation: Given data, Q = 250 lit/capita/day
Sewage flow = 75% of water supply = 0.75* 250 = 187.5 LPCD
Total sewage generated = 187.5*60000/(24*3600) = 130.21 lit/sec = 0.13 m3/s
Assume peak factor = 2
Total design discharge = 0.26 m3/s.

6. Pick up the correct statement in case of water supply.
a) Pipes laid in trenches and pipes fixed to walls are measured separately
b) Cutting through walls and floors are included with the item
c) Pipes are classified according to their sizes and quality
d) Pipes laid in trenches, cutting through walls and pipes classified as per size

Explanation: The product, delivered to the point of consumption, is called potable water if it meets the water quality standards required for human consumption.
The water in the supply network is maintained at positive pressure to ensure that water reaches all parts of the network, that a sufficient flow is available at every take-off point and to ensure that untreated water in the ground cannot enter the network. The water is typically pressurised by pumps that pump water into storage tanks constructed at the highest local point in the network. One network may have several such service reservoirs.
In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a water-tower or any other heightened water reserve to supply the water pressure.
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7. Cost of fittings and their fixing is specified for the following sanitary fittings.
a) Water closets
b) Flushing pipes
c) Lavatory basins
d) Water closets, Flushing pipes and lavatory basins

Explanation: A fitting is used in pipe systems to connect straight pipe or tubing sections, adapt to different sizes or shapes and for other purposes, such as regulating (or measuring) fluid flow. “Plumbing” is generally used to describe the conveyance of water, gas, or liquid waste in domestic or commercial environments; “piping” is often used to describe the high-performance (high-pressure, high-flow, high-temperature or hazardous-material) conveyance of fluids in specialized applications. “Tubing” is sometimes used for lighter-weight piping, especially that flexible enough to be supplied in coiled form.
Fittings (especially uncommon types) require money, time, materials and tools to install, and are an important part of piping and plumbing systems. Valves are technically fittings but are usually discussed separately.

8. What is the detention period in a septic tank?
a) 24 hours
b) 12 hours
c) 06 hours
d) 36 hours

Explanation: Detention period of 24hrs (mostly) considered in septic tank design. The rate of flow of effluent must be equal to the rate of flow of influent.

9. What is the diameter of a domestic sewer pipe laid at gradient 1 in 100?
a) 150 mm
b) 250 mm
c) 120 mm
d) 80 mm

Explanation: Following are some recommendations for domestic sewer pipe.
100 mm – 1 in 60.
150 mm – 1 in 100.
200 mm – 1 in 120.

10. Disinfection of drinking water is done to remove odour.
a) True
b) False

Explanation: Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill.

11. Fluctuation in flow occurs from hour to hour and from season to season.
a) True
b) False

Explanation: Variation occurs in the flow of sewage over annual average daily flow. Fluctuation in flow occurs from hour to hour and from season to season. If the flow is gauged near its origin, the peak flow will be quite pronounced. The peak will defer if the sewage has to travel long distance. This is because of the time required in collecting sufficient quantity of sewage required to fill the sewers and time required in travelling.

12. The per capita sewage generation can be considered as 35 to 50% of the per capita water supplied per day.
a) True
b) False

Explanation: The per capita sewage generation can be considered as 75 to 80% of the per capita water supplied per day. The increase in population also result in increase in per capita water demand and hence, per capita production of sewage. This increase in water demand occurs due to increase in living standards, betterment in economic condition, changes in habit of people, and enhanced demand for public utilities.

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