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Thread: Flow from a 4" Bottom Drain

  1. #1
    Tosai
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    Flow from a 4" Bottom Drain

    What is the minimum flow from a 4" aerated bottom drain for it to be effective in collecting waste?

  2. #2
    Nisai KDSD's Avatar
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    The minimum flow is 3000 on a 4" pipe, now it depends on how much your flow rate your doing by the pump and also the size of the pre-filter to handle that needed flow. Don't forget the skimmer if tied into pre-filter. If your pond is larger then 5000 gals then you may want to consider a second drain which would up the flow to 6000 gph. I alway use a 4" pipe in case you want to up grade then its there. Hope it helps.......................

    1-1/2" = 350 gph
    2" = 750 gph
    3" = 1500 gph
    4" = 3000 gph


    Koiman™
    CDKPA
    Last edited by KDSD; 02-07-2008 at 05:55 PM. Reason: should have been "minimum"
    Koiman™
    CDKPA

  3. #3
    Tategoi The Pond Digger's Avatar
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    Max Flow?

    Are we talking gravity flow or direct suction? I am assuming most all (99.9%) of the applications here will be GRAVITY FLOW. I just want to clarify the question.

    The question as I see it is, MINIMUM flow rate in an aerated 4" bottom drain. I suppose it is relative to what you are flowing into, yes or no?

    It is my understanding that the MAXIMUM flow rate into a 4" gravity flow bottom drain is 3600 GPH and a 3" bottom drain is 1800 GPH.

    So the original question. What is the MINIMUM recommended flow rate for an aerated 4" bottom drain?

    If I may, add to the topic -

    What is the OPTIMUM flow rate into a 4" aerated bottom drain?

    For example, what I have soaked up is - The Large Nexus filter is designed for a 4" feed and in doing so, puts a MAXIUM SPEED LIMIT on that filter of 3600 GPH. I have not read the manual personally but have talked with several different sources regarding the performance of the filter. So in regards to the large NEXUS filter; What is the OPTIMAL flow rate recommended on a 4" gravity flow BD? Aerated or not?

    And Can we confirm - What is the MAXIMUM recommended flow rate for an aerated 4" gravity flow?

    Does the MINIMUM, OPTIMUM & MAXIMUM flow rate change when their is an air dome on the BD or does the air dome just optimize the sweeping of debris off the bottom of the pond into those flow rates?

    I hope this is not one of those questions that varies widely depending on whom you are talking. Cold hard numbers PLEASE...............

    Respectfully,

    The Pond Digger
    "Doubt sees the obstacles, Faith sees the way!"

  4. #4
    Tosai
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    My pond will be a 9x14x5 oval with a capacity of about 4,000 gallons. Can a 3" bottom drain adequately remove the debris from the bottom of such a pond? If so, assuming 1,500gph from the BD, can enough additional circulation be obtained through a skimmer (perhaps 1,000gph or 1,500gph) to have a healthy pond? At 1,000gph through the skimmer the turnover time would be a little less than 2 hours; at 1,500gph through the skimmer the turnover time would be about 1 hour and 20 minutes.

  5. #5
    Tosai
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    [quote=The Pond Digger;105447]Are we talking gravity flow or direct suction? I am assuming most all (99.9%) of the applications here will be GRAVITY FLOW. I just want to clarify the question.


    Yes, it would be gravity flow.

  6. #6
    Sansai
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    hello Gary i new wih hobby but i can tell you 3' pipe not enough it only carry 1800 gpm you need 5000 to 6000gpm due to 4000gl pond you have. it will be 1 bottom drain 4' about 3600 gpm and 2 skimmer 2' about 900gpm or one mid-water 3' about 1800gpm. i know it because i will have a pond like your pond

  7. #7
    Tosai
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    Hi, someone told me that for my shape and size of pond I should use two 3 inch BDs instead of one 4 inch. That would give me about the same total flow. However, I have heard that the effective debris sweep radius for a 4 inch BD is 6 feet. What is the effective sweep radius for a 3 inch BD?

  8. #8
    Sansai
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    how much you have to pay for 3 bottom 3' and did you ask for 4' yet?

  9. #9
    Tosai
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    I was told to use two 3 inch BD, not three. I haven't priced them yet.

  10. #10
    Tategoi The Pond Digger's Avatar
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    Sweeping.......

    It is my understanding that a 3" bottom drain is effective at sweeping a 6' to 8' diameter and pushing the limits to a 10' diameter, depending on who you talk to. Of course, if you are going to push to the limits, an air dome is highly recommended for effective sweeping. Where as a 4" BD would effectively sweep a 10' to 12' diameter for optimal sweeping and a 14' diameter would be pushing the limits.

    Now mind you, we are assuming the bottom of the pond should always be bowled down to the lowest depth of the pond where the BD would be installed for the most effective sweeping of debris for removal from the pond.

    I suppose this information is all subjective depending on what the MINIMUM, OPTIMUM & MAXIMUM flow rates are being used, what you are flowing into, how heavy your fish load is, how much leaf debris you pond is subjected too, if you are raising male or female koi, and again of course who you are talking to.

    But what do I know? Look what happens if I stay up to late on the computer

    With All Due Respect,

    The Pond Digger

    P.S.

    I'll go pick out a switch..............

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