gravity underground sand filter

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Bonnan, Jun 17, 2011.

  1. Bonnan

    Bonnan New Member

    Messages:
    5
    Location:
    pa
    Looking for info to clean up cistern water before it is pump into my buildings.
    This is roof collected water not used for human consumption but must be reasonably sediment free. How does one design/build a sand filter for this purpose. Thanks for any help
  2. gritres

    gritres New Member

    Messages:
    56
    Location:
    nw florida
    do you really get enough sediment off a roof to justify a sand filter? maybe just use a spin down filter
  3. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,185
    Location:
    NW Ontario, Canada
    How well a sand filter works by gravity would depend on how much head the water has. At some point I would think you'd need a pump to backwash the sand filter. Something like a swimming pool filter might work. Pond filters are another consideration.
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,508
    Location:
    Houston, TX
    Like LLigetfa was saying, You would need a way to backwash a sand filter.

    You may want to use something like a filter material used in pond filtration systems.
    You can buy it in large sheets, and cut to fit. Put in into a 5 gallon bucket with a IN/OUT connection and a locking lid.

    Then when the filter gets dirty, you take the material out and rinse it using a garden hose.

    I have built these before, but they are only for low pressure. High pressure will blow the lid off of the bucket when the filter get dirty.

    Should work good for gravity a system, and is cheap to build.


    DonL
  5. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    dig a hole and line it with EPDM and fill it with sand. thats how septic tanks sand filters work. You could even backwash it - you would build a distribution grid of pipe with drilled holes in the bottom of it.

    Frankly, a big cow water tank would be easier to deal with. Need a lid though. grade sand at botttom to pea gravel to gravel at the top.
  6. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,185
    Location:
    NW Ontario, Canada
    Would you not want to reverse the gradient, putting coarser on bottom and finer on top? That is how a septic leach bed is setup.

    I am considering sinking a couple of well rings at the end of where my underground pipes draining my rain gutters break to the surface. I'd just use a pond filter and a old pitcher hand pump to draw the water. I have solid clay so wouldn't even need to line it with EPDM.
  7. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Yeah, you got me reversed, the gravel is to keep from washing the sand through the pipe holes. The size gradient is important.

    Or you could use a filter cloth.

    But actually a standard septic leach line with 4" perf is all 1.5" and a bit under.
  8. Smooky

    Smooky Member

    Messages:
    649
    Location:
    NC
    I found good information and diagrams for this type of slow sand filter in "Environmental Engineering And Sanitation" by Joseph A. Salvato, P.E. I have the third edition.
  9. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,508
    Location:
    Houston, TX
    Do you care to share Smooky ? Or are you just teasing ? LOL.


    DonL
  10. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    A simple small gravity feed plastic or metal tank will work. Feed the rain/roof water in the side of the tank and out from the top. Install a pipe plug (or ball valve) at the bottom and drain the sand out every six months to a year. This will work for all heavier than water debri trash.
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