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  1. #1
    Senior Member princpl skimmer's Avatar
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    overflow and return gph

    ifi have an overflow rated at 600 gph max, can i have a mag7 as a return IF i have 5 feet of head? will 5 feet slow the pump down to 600 gph or is that being to risky?

  2. #2
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    The Reef Central head loss calculator reports that a Mag 7 with 5 feet of head will flow about 400GPH.
    Nick

  3. #3
    Moderator Krugar's Avatar
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    Correct me if I'm wrong, but doesn't the system slow down to what the pump can do?

    i.e. if you're pumping 400GPH back into the tank, your 600GPH overflow only has 400GPH to work with.

    Of course your sump has to be able to handle the inital "surge".

    Does that sound right?

    Cheers!
    There is nothing so permanent as a temporary measure.

  4. #4
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    The 5' of head will reduce the pump flow from 700 GPH to about 400-450GPH.

    As you say, the pump return rate will determine the overflow rate. The overflow rating is ust a maximum estaimted capacity.
    Nick

  5. #5
    Moderator cres's Avatar
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    Yes. But, his question is the other way.

    If you have 600 GPH drain capacity and 700 GPH going in ... well, that is a wet floor and burned out pump waiting to happen.

    The 700 will drop as the head increases, but, he is concerned that it might not drop to a safe level.

    I think it'll be okay.
    Sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.

  6. #6
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    I'm confused here.

    The original question was whether a 600GPH rated overflow could handle a Mag7 with 5' of head. That would be 'yes' since the head reduces the flow to 400GPH which the overflow can handle.

    As a secondary question, what happens if the pump returns more than the overflow rating? That would be a problem. The water level would rise in the tank which would increase flow in the overflow but could lead to floods, etc. as 'cres' says.
    Nick

  7. #7
    Moderator cres's Avatar
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    I hope >I< didn't confuse you Nick, we posted simultaneously.

    I was speaking to Krugar, who correctly asserted that the overflow will match the return flow, but, I believe that Principal Skimmer was wondering if the Mag 7 (700 GPH max) with 5' of head wouldn't be too much for the return (600 GPH max).
    Sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.

  8. #8
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    You would be best to run the pump on the shortest possible length of pipe and use a valve to control water flow to the tank. The excess water can be diverted back into the sump, an existing or future refuge or some other future piece of equipment.
    Rob

  9. #9
    Moderator Krugar's Avatar
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    Okay but isn't that one of the reasons there's baffles in your sump? If for some reason the pump does get ahead of the overflow, it should only be albel to empty out down to the baffle.

    At which point you'd hopefully have a float switch to turn it off before it starts running dry.

    Sorry if I'm making things too complex, I haven't built my sump yet & I'm trying to make sure I understand.

    Cheers!
    There is nothing so permanent as a temporary measure.

  10. #10
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    No .. .the baffles are to control bubbles and the direction that water moves through the sump. You DO NOT WANT YOUR PUMP TO RUN DRY in any case. Float switches go in the compartment when the pump is or draws water from.
    Rob

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