Note of Water Supply Engineering

 

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  • The  cast iron water mains are very durable.
  • As compared to cast iron pipes, steel pipes are stronger.
  • In the design of pressure conduits for water supply, the large value of design velocity, if adopted will reduce the cost of conduit and increase the cost of pumping.
  • The commonly used material for water supply pipes, which has the property of being strong, not easily corroded, long life but heavy and brittle in cast iron.
  • Steel pipes are liable to quick rusting, easily affected by acidic and alkaline atmospheric effects, and unable to withstand high negative pressures.
  • Cast iron pipes which are cast in horizontal position by ordinary process in sand molds are called Mc Wane pipe.
  • Life span of cast iron pipes is around 100 years.
  • Cast iron pipes having plain ends are joined by dresser coupling.
  • Flanged joints are provided for cast iron, steel and galvanized iron pipes.
  • For asbestos cement pipes the joint which is commonly  used is ring-tite coupling or simplex joint.
  • For cement concrete pipes with plain ends the joint commonly  used is cement collar joint.
  • Water is considered ‘soft’ if its hardness does not exceed 50 ppm.
  • If total hardness of water is greater than its total alkalinity, the non-carbonate hardness will be equal to total alkalinity.

 

 

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  • If total hardness of water is less than  its total alkalinity, the carbonate hardness will be equal to total hardness.
  • If total hardness of water is less than  its total alkalinity, the non-carbonate hardness will be equal to total zero.
  • The main disadvantage of hard water is that it causes more consumption of soap.
  • Hardness of water can be removed by boiling if it is due to calcium bicarbonate.
  • Alkalinity in water is expressed as milligrams per litre in terms of equivalent calcium carbonate.
  • For boilers water to be used should preferably be soft.
  • Breweries and distilleries preferably require hard water.
  • The test of hard water is better than that of soft water due to presence of bicarbonates.
  • The safe permissible limit of chloride in domestic water supplies is 200 mg/l.
  • The presence of excess amount of nitrates in drinking water may cause a disease called methemoglobinemia.
  • The safe permissible amount of nitrates in domestic water supplies is 45 ppm.
  • For drinking water the amount of free ammonia should not exceed 0.15 ppm.
  • When fluoride concentration in water exceeds 1.5 mg/l , the disease that may be caused is fluorosis.
  • When fluoride concentration in water is less than about 1.0 mg/l, the disease that may be caused is dental carries in children.
  • Dental carries in children may be caused due to water supplies which are deficient in fluoride.
  • Blue baby disease may be caused in infants due to drinking water containing higher concentrations of nitrates.
  • The only metal among the following which is toxic to human beings is arsenic.
  • The only metal among the following which is not toxic to human beings is sodium.
  • The safe permissible limit of concentration of iron in domestic water supplies is 0.1 ppm.
  • The safe permissible limit of sulphates in domestic water supplies is 200 mg/l.

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