225.  In pressure supply mains, water hammer pressure is reduced by providing
A. sluice valves
B. air valves
C. pressure relief valves
D. none of the these.

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226. Manholes along the mains from the source to a city are provided at 500 m intervals in
A. steel pipes
B. R.C.C. pipes
C. hume steel pipes
D. all the above.

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227.  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).

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228.  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 4
B. D = 1.22 Arei
C. D = 2.22 Nrq
D. D = 3.22 4

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229.  If w is the weight of water per cubic metre; Q is the discharge in cubic metres per sec and H is the total head, the required water horse power of the pump, is
A.150wQH
B.220wQH
C. 360wQH
D. 550wQH

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230.  If discharge of a pump is 0.16 cumecs, the economic diameter of pipe, is
A. 0.488 m
B. 4.88 cm
C. 48.8 cm
D. 4.88 m

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231. Standard unit of turbidity of water is in one litre of distilled water, one milligram of finely divided
A. silica
B. mud
C. clay
D. organic matter,

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