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City Water supply pressure

  1. May 2, 2010 #1
    In plumbing we need to know the pressure in the city main supply , my question is how can the city give us the minimum pressure of its supply for our building lets say before pluging in our whole plumbing system to the city main line ???

    usually the pressure at a node is determined when it is connected to a system , if we add anything to the system lets say a new floor with new fixtures the pressure at the same node will change to balance the whole system , so how the pressure of the city wall supply is determined to the engineer before he design his system ???
  2. jcsd
  3. May 2, 2010 #2
    The relationship between the large bore city supply pipes and the much smaller bore individual building supplies act in the same way as a manifold in a central heating system supplying multiple small bore pipes to individual radiators.

    The difference between the bore of the city pipe and the bore of the building supply is such that pressure at their junction is unaffected by any flow takeoff to the building.
  4. May 3, 2010 #3
    do you mean that the pressure of the supply from the city pipeto my buliding dosent change when my building piping grid is installed ???
  5. May 3, 2010 #4
    There are two things that will affect the water pressure in the building. One being the flow of water, where pressure at the valve/faucet/whatever will decrease with an increase in total flow rate. The second being height, how high the water is from the pumping station.

    So if your system has no water flowing through it, as in all sinks toilets and what ever are not being used, the pressure at the node will not change no matter what you add to your piping system.
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