Multiple Choice Questions and Answers (MCQs) on Water Supply Engineering

01. When the reduced level of the water source is higher than the reduced level of the consumer’s place, water is generally supplied

(A) By pumping system
(B) By gravitational system
(C) Both (a) and (b)
(D) All the above

02. Surcharge storage zone of a reservoir, is

(B) Between dead storage and useful storage
(C) Above useful storage
(D) Also known as valley storage

03. In pressure supply mains, water hammer pressure is reduced by providing

(A) Sluice valves
(B) Air valves
(C) Pressure relief valves
(D) None of these

04. Specific capacity or yield of wells, is generally expressed, as

(A) m3 per sec
(B) m3/hour
(C) m3/hour/m2
(D) m3/hour/m2/m

05. To pump water from a water reservoir 3 m deep and maximum water level at 135 m, a pump is installed to lift water up to R.L. 175 m at a constant rate of 36,00,000 litres per hour. If the length of the pipe is 1506 m and f = 0.01, ignoring other minor losses and assuming the economical diameter from Lea’s formula D = 1.2 √Q, the water horse power of the pump is

(A) 400
(B) 450
(C) 500
(D) 600

06. Turbidity of raw water is a measure of

(A) Suspended solids
(B) Acidity of water
(C) B.O.D.
(D) None of these

07. If the chosen diameter of a pipe, is less than the economical diameter

(A) Cost of pipe will be less
(B) Head loss will be high
(C) Cost of pumping will be more than saving
(D) All the above

08. Pick up the correct statement from the following:

(A) The water level in a still well, represents the ground water table level
(B) The difference between water table level and the water level in a well after pumping, is called depression head
(C) The surface of water table surrounding a well during pumping, forms a cone of depression
(D) All the above

09. The expected discharge to be obtained from an open well sunk in coarse sand is 0.0059 cumec. If the working depression head of the well is 3 m, the minimum diameter of the well, is

(A) 2 m
(B) 2.25 m
(C) 2.50 m
(D) 3.00 m

10. Pick up the correct statement from the following:

(A) Water with hardness upto 75 ppm is considered soft
(B) Water with hardness more than 200 ppm is considered hard
(C) Water needed for laundries should contain hardness less than 75 ppm
(D) All the above

11. In centrifugal pump installation,

(A) Pump is properly primed before starting
(B) The diameter of the pipe at inlet as well as at outlet, is kept smaller than the delivery pipe
(C) The motor may burn out if it is started with empty delivery pipe and with open gate valve
(D) All the above

12. While determining the yield of open wells by the pumping test

(A) Velocity of recharging water, increases with depression head
(B) Depression head resulting at critical velocity, is called critical depression head
(C) Working head is generally limited to ⅓rd of the critical depression head
(D) Maximum safe yield of an open well, is expected at critical depression head

13. The process of passing water through beds of granular materials, is called

(A) Screening
(B) Sedimentation
(C) Filtration
(D) None of these

14. For the prediction of future population of a city, the factor to be considered, is

(A) Births
(B) Deaths
(C) Migrants
(D) All the above

15. Mathamoglobinemia or blue baby disease is caused due to

(A) Chlorides
(B) Nitrites
(C) Nitrates
(D) Sulphides

16. To control the growth of algae in reservoirs, the compound which is used, is

(A) Bleaching powder
(B) Copper sulphate
(C) Lime solution
(D) Alum solution

17. The population of a city in 2000 is 50,000. The average increase in population over last 8 decades is 7500 and average incremental increase during 8 decades is 750. The population of the city based on incremental method, in the year 2020 will be

(A) 55,000
(B) 60,500
(C) 66,500
(D) 72,500

18. A pressure conduit laid underground, may not be subjected to

(A) Internal pressure of water
(B) Pressure due to external load
(C) Longitudinal temperature stress
(D) Longitudinal stresses due to unbalanced pressure to bends

19. The bacterias which require free oxygen for their survival, are called

(A) Aerobic bacterias
(B) Anaerobic bacterias
(C) Facultative bacteria
(D) None of these

20. Gravity conduits are generally in the form of

(A) Canals
(B) Flumes
(C) Aqueduct
(D) All the above

21. The main disadvantage of hard water, is

(A) Greater soap consumption
(B) Scaling of boilers
(C) Corrosion and incrustation of pipes
(D) All the above

22. The formula Q = P – K [1.8T + 32] in which Q is runoff, P is annual rain fall in cm, T is mean annual temperature in centigrade and K is a constant, is known

(A) Justin’s formula
(B) Khosla’s formula
(C) English formula
(D) Vermule’s formula

23. The bed slope in slow sand filters, is generally kept

(A) 1 in 50
(B) 1 in 75
(C) 1 in 100
(D) 1 : 200

C 24. The water level in an open well was depressed by pumping 2.5 m and recuperated 2.87 m in 3 hours and 50 minutes. The yield of the well per minute is

(A) 0.0033
(B) 0.0044
(C) 0.0055
(D) 0.0066

25. Perched aquifers are generally found

(A) On the surface of the ground
(B) Below the surface of the ground but above water table
(C) Below the water table
(D) All the above

26. Pick up the incorrect statement from the following:

(A) The pH value of water indicates the logarithm of reciprocal of hydrogen ion concentration in water
(B) Higher value of pH means lower hydrogen ion concentration
(C) Lower value of pH means higher hydrogen ion contraction
(D) Lower value of pH gives alkaline solution

27. Mostly used coagulant, is

(A) Chlorine
(B) Alum
(C) Lime
(D) Bleaching powder

28. A centrifugal pump is required to be primed before starting if it is located

(A) At higher level than water level of reservoir
(B) At lower level than water level of reservoir
(C) Both (a) and (b)
(D) Neither (a) nor (b)

29. Suction lift of a pump depends upon

(A) Atmospheric pressure
(B) Water temperature
(C) Velocity of water in suction pipe
(D) All the above

30. Normal values of overflow rate for plain sedimentation tank, is

(A) 250 to 500 litres/hr/m2
(B) 500 to 750 litres/hr/m2
(C) 750 to 1000 litres/hr/m2
(D) 1000 to 1250 litres/hr/m2

31. ‘Shrouding’ is essentially provided in

(A) Strainer type wells
(B) Cavity type wells
(C) Slotted type well
(D) All the above

32. The maximum permissible hardness for public supplies is

(A) 95 mg/litre
(B) 105 mg/litre
(C) 115 mg/litre
(D) 125 mg/litre

33. Time of concentration

(A) Is the time taken, for precipitation
(B) Duration of rainfall
(C) Time taken for all the ran off to reach the drain
(D) Time taken for the storm water to travel from the most remote point to the drain

34. The chlorine supply cylinders are generally kept at 38°C to 40°C to prevent

(A) Conversion into crystals
(B) It from burning
(C) It from explosion
(D) None of these

35. For calculation of economical diameter D of a pipe in metres for a discharge Q to be pumped in cumecs, Lea suggested the empirical formula

(A) D = 0.22 √Q
(B) D = 1.22 √Q
(C) D = 2.22 √Q
(D) D = 3.22 √Q

36. An earth formation which, although porous and capable of absorbing water does not provide an appreciable supply to wells, is known as

(A) Aquifer
(B) Aquiclude
(C) Aquifuge
(D) None of these

37. Property of earth to allow water to pass through it, is known as

(A) Perviousness
(B) Porosity
(C) Permeability
(D) Transmissibility

38. Plain chlorination is used for water

(A) Obtained from clear lakes
(B) Consumed during emergencies
(C) Supplies to armies during war
(D) All the above

39. A city supply includes

(A) Domestic water demand
(B) Industrial and commercial water demands
(C) Demand for public uses and fire
(D) All the above

40. The pH value of water is kept slightly less than 7 so that hydrochloride ions may combine with ammonia ions to form

(A) Mono-chloramine (NHCl)
(B) Di-chloramine (NH2Cl)
(C) Nitrogen tri-chloramine (NCl3)
(D) All the above

41. Pick up the correct statement from the following:

(A) Copper pipes are highly resistant to acidic and alkaline water
(B) Wrought iron pipes are lighter than cast iron pipes
(C) Wrought iron pipes corrode quickly and are less durable
(D) All the above

42. Pick up the correct statement from the following:

(A) A hydrograph is a plot of discharge versus time
(B) A mass curve is a plot of accumulated flow versus time
(C) The mass curve continuously rises
(D) All the above

43. If L, B and D length, breadth and depth of water in a rectangular sedimentation tank of total discharge Q, the settling velocity, is

(A) Q/H
(B) Q/D
(C) Q/(D × B)
(D) Q/(L × B)

44. The difference in the reservoir level and the lowest point of the water mains is 180 m. The expected pressure due to water hammer is 7.5 kg/cm2 in a pressure conduit of diameter 1 m. Assuming the efficiency of the riveted joints of the pipe as 0.6 and minimum cover 3 mm for corrosion, the thickness of the pipe materials, is

(A) 10 mm
(B) 15 mm
(C) 20 mm
(D) 25 mm

45. If G is the specific gravity of particles of diameter d, the velocity of settlement V in still water at T°C, according to Stoke’s law, is

(A) V = 418 (G – 1) d² [(3T + 70)/100]
(B) V = 418 (G – 1) d [(3T – 70)/100]
(C) V = 418 (G – 1) d² [(2T + 70)/100]
(D) V = 418 (G – 1) d4 [(3T + 70)/100]

46. Rapid gravity filters

(A) Were developed by G.W. Fuller
(B) Make use of coarser sand with effective size as 0.5 mm
(C) Yield as high as 30 times the yield of slow sand filters
(D) All the above

47. For 3.25 × 10-2 cumecs discharging from a well, a pump is installed to lift water against a total head of 30 m. The minimum required horse power, is

(A) 10 H.P.
(B) 15 H.P.
(C) 18 H.P.
(D) 20 H.P.

48. Distribution mains of any water supply, is normally designed for its average daily requirement

(A) 100 %
(B) 150 %
(C) 200 %
(D) 225 %

49. Maximum threshold number permitted for indicating the odour of public water supplies, is

(A) 1
(B) 2
(C) 3
(D) 4