267. It is customary to design a sewer for D.W.F. on the basis of
A. average demand
B. twice the average demand
C. thrice:the average demand
D. four times the average demand.

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268. For design purposes, the normal rate of infiltration of ground water into the sewer, is
A. 500 litres/km/cm
B. 1000 litres/km/cm
C. 1500 litres/km/cm
D. 2000 litres/km/cm

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269. The gradient of sewers depends upon
A. velociy of flow
B. diameter of the sewer
C. discharge
D.all the above.

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270.  The minimum diameter of a sewer is kept
A. 10 cm
B. 15 cm
C.20 cm
D. 25 cm

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271.  The suitable cross-section of sewers to carry combined ,flow, is
A. circular
B. egg shaped
C. rectangular
D. horse shoe shaped.

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272. For disposal of discharge by separate system, the recommended cross-section of sewers is :
A. circular
B. egg shaped
C. rectangular
D. horse shoe shaped.

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273.  Setting out the alignments of sewers may start from
A. city
B. out-fall
C. tail end
D. any point.

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