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Water pressure in multiple tanks

  1. Aug 10, 2010 #1
    hi - i am new so forgive any errors.
    question is this. if a number of water tanks are stacked one on top of the other. and each share the same downpipe with a tap at ground level. When the tap is opened which tank will drain first and why?

    many thanks.
  2. jcsd
  3. Aug 11, 2010 #2
    shouldn't they be drained at the same rate?
  4. Aug 11, 2010 #3


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    In the initial state with the tap closed, why isn't water flowing from the higher tanks into the lower tanks like normal siphon process?
  5. Aug 11, 2010 #4
    i think u should use an illustration to show how are the tanks connected
  6. Aug 11, 2010 #5
    The top tank will drain first, since the tanks below it would be refilled from the tank above, were their levels to go down.
  7. Aug 11, 2010 #6
    thanks for replies so far. but clearly i have not given enough info.
    the tanks are all full. they are each connected to a single downpipe. Each connector has a one way flow valve. so water cannot flow from one tank into another. in that scenario when the tap at ground level is opened all the tanks will compete to discharge their volume. i would just like some guidance on which would empty first. and of course why. t

    thanks again.
  8. Aug 11, 2010 #7
    I think the pressure from (on?) the highest tank would cause it to drain first as that pressure would keep all your lower check-valves closed. In fact I would hazard to go further out on the limb and say that the check-valves are superflous.
  9. Aug 11, 2010 #8


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    The one way valves will not open until pressure outside the valve is lower than pressure inside the valve, so until all water above any current tank's water level is drained, the valve for that tank will not open. The top tank drains first, then the water in the pipe above the 2nd tank drains next, then the 2nd tank and water in the pipe just below level of water in 2nd tank drains, ...
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