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Thread: GPM Formulas

  1. #1
    MembersZone Subscriber
    Join Date
    May 2000
    Lincoln, NE

    Question GPM Formulas

    Could someone assist me in understanding the NFF and the Iowa Formulas? LWH/100...is that equal to the minimum GPM needed if the structure were fully involved? Same with lw/3...is that the same thing? Or is it the total volume of water needed to "fill the structure with water?"

    Thanks for your help...Tim

  2. #2
    MembersZone Subscriber firefighterbeau's Avatar
    Join Date
    Aug 2003
    Central ND USA


    If I remember correctly them are both to control the fire. I believe the Iowa formula is a bit older, and most of the time I have been told to use the NFF one.

  3. #3
    Join Date
    Feb 2005


    I dont know if this will help since Im a pretty new vollie, but for a structure fire I thought your GPM was LxW/3 for a fully involved fire, and from that you could figure what you would need for any other percent of involvment. Also you would add 25% for exposures that are in danger. If this is wrong, or I wrote this wrong, I would like to know, since its always good to have the best knowledge possible.

  4. #4
    Junior Member
    Join Date
    Mar 2004


    The Iowa flow formula is correct, and it is the flow required for full involvement of the structure, the formula though was developed in the late 50's when the fire load was about half of what it is today! The NFF is probably closer to reality.

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