Saturday, August 9, 2014

Various types of Water Demands Formulae

Hi, How you doing?  In our previous article 'Introduction to Water Demands', we got introduced with the various types of water demands, in this article I will post the various formulae which are used to calculate the water demands in cities of different kinds.

  • Fire Demand
Let's Q be the demand of water required in liters/minute. Rate of fire demand is sometimes treated as a function of population and is worked our on the basis of the empirical formulas:
  • (1) Kuichling Formula





Where, Q = Amount of Water required in liters/minute.
P = Population in thousands.

  • (2) Freeman Formula







  • (3) National Board of Fire Under Writers Formula
(a) For a central congested high valued city
       (i) Where population < 200000




       (ii) Where population > 200000
            Q = 54600 lit/minute for first fire
     and  Q = 9100 to 36, 400 lit/minute for a second fire.
(b) For a residential city.
       (i) Small or low building,
            Q = 2,200 lit/minutes.
       (ii) Larger or higher buildings,
            Q = 4500 lit/minute
       (iii) High value residences, apartments, tenements
            Q = 7650 to 13,500 lit/minute.
       (iv) Three storeyed buildings in density built up sections.
            Q = 27,000 lit/minute.

  • (4) Buston's Formula







  • The probability of occurrence of fire, which, in turn, depends upon the type of the city served, has been taken into consideration in developing above formula on the actual water consumption in fire fighting for Jabalpur city of India. The formula is given as:

    Where, R = Recurrence interval of fire i.e., period of occurrence of fire in years, which will be different for residential, commercial and industrial cities.

    (R) minimum = 1 year.
       t = duration of fire in minutes,
      (t)minimum = 30 minutes.

    • Per Capita Demand(q)
    q = Total yearly water requirement of the city in liter/ (365* Design population)

    Thanks for your kind visit!

    References:  Book - A Handbook on Civil Engineering IES, GATE, PSUs - Made Easy