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Water drainage rate through soil.

  1. Nov 10, 2012 #1
    I'm designing the attached aquaponic system and am trying to estimate the speed at which water will drain through the pipes. Basically, water enters the top of the pipe, then drains through roughly 5 feet of soil before it exits the pipe. Is there a way to estimate the speed at which the water will drain? I feel like it depends heavily on the type of soil. I was planning to use just your typical potting soil that you buy a a gardening store. Thanks!

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  3. Nov 10, 2012 #2

    Simon Bridge

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    This is something you are best to determine empirically... do an experiment.
    The drainage rate also changes over time.
  4. Nov 10, 2012 #3
    Thanks Simon, I wouldn't have thought of that :).
  5. Nov 12, 2012 #4
    This is a problem in "flow through porous media." You need to measure the permeability and porosity of a typical soil sample in an appropriate standardized piece of equipment. The porosity is the volume fraction of voids, and the permeability is characteristic parameter that allows you to calculate the fluid flow per unit area through a sample of a certain length, for a fluid of a specified viscosity, and for a specified pressure drop. See a book on flow through porous media, or start by looking in Transport Phenomena by Bird, Stewart, and Lightfoot. This is methodology that is extensively used by the groundwater people and by the oil and gas people. Look for a book with the title Groundwater. I forgot the authors' names.
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