1. #1
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    Default Supply Line From A 375 Gpm

    I've got an old truck with a 375 GPM pump. i would like to get some feedback on this: if i lay a 100' x 2.5" line, can i get full capacity out of that pump? or should i use (2) 2.5" lines. i just know that you can put a heck of a lot of water through a 2.5" line at 100', but would it be easier on the pump if i ran two lines, or would (1) line take all that the pump can produce?
    thanks,
    Justin R McGuigan
    Fire Chief, Millville FD

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    Well I dont know if this will help, but here goes anyway.

    I think it would be better to use a dual 2.5 lay for max flow with less friction loss.

    Good luck with that.
    Rath De Ort

    RSM

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    First a question - are you going to be supplying the 2.5" with your tank, from a draft or from an external presserized source such as a hydrant?
    Given that the maximum flow of a 2.5" is about 250 gpm, you would be better off to lay 2 lines. If you are being supplied from a pressurized source, you also may actually be able to flow more than the rated capacity of your pump. Even at a draft, if your pump is in goode shape and you are fairly close to the water source, you may be able to draft at slightly over pump capicity. If you are pulling from your tank, it's doubtful you will flow 375 gpm as most tank to pump lines in older trucks are only 2.5"
    Hope this helps.

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    If it is of any use to you... we have done some flow tests and found that if you run 3" hose with 2.5" couplings, you can get a much better flow out of the hose. The flow improves with a 4" hose... but I don't have the numbers in my head. The ease in deploying just one hose might justify the difference in flow between one or two 2.5" hoses if it flows close to the same GPM.
    Richard Nester
    Orrville (OH) Fire Dept.

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    ------------------------------------------------
    quote:
    Given that the maximum flow of a 2.5" is about 250 gpm
    ------------------------------------------------

    Perhaps you mean from a non-pressurized supply. I agree with the premise, if you have the ability, lay the dual lines. However,
    2 1/2" hose can flow much more than 250 pgm.

    Example - Supply a portable moniter with 2" tip with dual 2 1/2" lines. Pump 130 psi. Result 1000 gpm. That would be 500 gpm per line which is more than 250.

    If your on a good plug and only 100' away, a flow of 300-400 gpm should absolutely be obtainable.
    RK
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    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

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    Originally posted by MemphisE34a
    ...if you have the ability, lay the dual lines. However,
    2 1/2" hose can flow much more than 250 pgm.

    Example - Supply a portable moniter with 2" tip with dual 2 1/2" lines. Pump 130 psi. Result 1000 gpm. That would be 500 gpm per line which is more than 250.

    If your on a good plug and only 100' away, a flow of 300-400 gpm should absolutely be obtainable.
    I agree with you, but maybe it's easier to think of it this way...

    At 375 gpm, 2 1/2" line has friction loss of about 30 psi per 100'. So, assuming your hose is tested to the usual 200 psi, you can go for about 600' while flowing capacity on this 375 gpm rig before exceeding standard test pressure of the hose (NOTE: I'm assuming your hose is tested regularly and you test it to 200 psi. If not, pump these pressures at your own risk!). At the same time, if you lay out dual 2 1/2" lines, you'll be flowing just under 190 gpm per line, with a friction loss of about 8 psi per 100' on each side. In that case, you could (theoretically) flow your 375 gpm over 2500' of dual 2 1/2" before reaching the 200 psi test pressure, although I'm not sure what the practical application for this is (Who in the world carries 5000' of 2 1/2" hose?? How big would that hose bed have to be??).

    So, what I'd say is this...for lays of 500' or less, you can comfortably flow your 375 gpm pump capacity through one 2 1/2" line. If you lay out dual 2 1/2" lines and use two separate discharges, you can probably pump your capacity as far as you could conceivable want (or need) to without much problem. For example, required discharge pressure for 1000' of dual 2 1/2" lines at 190 gpm each (380 gpm total) would only be about 80 psi. All of this, of course, assumes you can get the 375 gpm into the pump in the first place, but that depends on your source and what hardware you have for that job.

    Hope this helps...
    Last edited by bobsnyder; 02-25-2005 at 03:18 PM.

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    Hey Chief, get the guys out, get a pitot gauge and set it up, see what you can get. Then you'll be sure of what you can do. Not to mention a good, hands on training evolution for you.
    And, 375 gpm through a 2.5" line 100' long.....I'd guess 35 - 40 PSI friction loss, depending on the condition of the hose. Shouldn't be a problem to get that.

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    Smile flowrate

    hey chief
    if i read your question right and you lay 100'of 2 1/2 all the calculations are based on your supply or source ie hyd,pond,lake,pressurized or drafting. static and residual pressuer from a hyd.and volume and discharge pressuer from a draft . if you have at least 70psi static at the source you should have no problem getting your 375 gpm flow.

    helping people,
    it's what we do!
    capt dennis

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    A guy from Pierce told me he has seen 750+ GPM through a 50' foot section of 2.5''

    Food for thought for everyone who is stuck on the 2.5'' hose = 250 GPM myth.

    It will flow much more if it is a short lay.
    FTM - PTB

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    As my Hero Capt Stanley use to say 'Lay duals down the alley eng 51,
    Squad 51 catch the plug'

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    You can push 500 gpm through one 2 1/2 and this will take about 150 psi to accomplish. Two 2 1/2 will decrease the the psi you have pump, do to the decrease in friction loss. A 2 1/2 has to beable to flow a minium of 250 gpm.

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