Thread: 3" Supply Line

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    Default 3" Supply Line

    I know this is probally been discussed somewhere else but.....

    What is the maximum amount of water I can get out of 1 3" supply line forward laid with no other pumper boosting pressure.

    Trying to justify going duel 3" or single 4".

    Will not probally be able to go 4 due to financial constrants.

    Current setup is 1200' of 3" supply. And need to know what I could probally get off what I already have.

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    Quote Originally Posted by osfd399 View Post
    What is the maximum amount of water I can get out of 1 3" supply line forward laid with no other pumper boosting pressure.
    Just so we're clear, you're talking about forward laid and connected to hydrant with no relay, correct?

    Well, your first limitation would be your hydrant capacity. Obviously, if you have a 500GPM-rated hydrant, you're not going to get any more than 500GPM.

    Secondly, hydrant pressure is a concern. If it can put out 1000GPM, but only does so at 50PSI, that shortens your range considerably.

    I remember in the Engineer section where we were talking about direct tank fill supply for AF ARFF apparatus, Fyred and I did some math, and we figured that you can flow about 1000GPM thru a single 3" line and incur about 60PSI of friction loss.

    SO, if your hydrant does 1000GPM at 80PSI (that's a really good hydrant, keep in mind), then if you lay 100' of single 3" into your intake, you should have 20PSI incoming at your intake, which is fine (it's what we aim for when doing shuttle ops, 20-25PSI at the intake)...but lay down even another 50' of supply line, and your intake pressure drops to virtually nothing, trying to flow that much water thru a single 3".
    300-500GPM is pretty doable, but much more than that and the friction loss will kill you over much more than 100' of hose.

    EDIT to add:

    If you have no choice but 3", then 3" to both aux intakes will work much better than single...the only problem is that you'll have to split your hosebed into two 600' beds of 3" each with its own finish. That's really not a bad thing, though, because it gives you the flexibility of a dual lay from hydrant, pulling both drops at the same time, or you could pull one set of drops, take off laying line, then when you run out, connect the drops of the 2nd bed into the first and make a long-lay if you know you're getting a relay.
    Last edited by the1141man; 07-29-2007 at 09:03 PM.
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    thank you. yes we are talking about a single lay with no relay operation. What kind of friction loss per 50' are we looking at?

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    Quote Originally Posted by osfd399 View Post
    I know this is probally been discussed somewhere else but.....

    What is the maximum amount of water I can get out of 1 3" supply line forward laid with no other pumper boosting pressure.

    Trying to justify going duel 3" or single 4".

    Will not probally be able to go 4 due to financial constrants.

    Current setup is 1200' of 3" supply. And need to know what I could probally get off what I already have.
    The performance of dual 3's versus single 4" is almost identical. The only difference is carrying 4" is less hose on the ground.

    What you need to know is what kind of flows your hydrants give you. If you have a hydrant that provides 500 GPM@40 PSI, you can move that 500 GPM somewhere in the range of 150 feet with no engine on the plug usign a single 3" line.
    Last edited by MG3610; 07-29-2007 at 09:21 PM.

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    Quote Originally Posted by MG3610 View Post
    The performance of dual 3's versus single 4" is almost identical. The only difference is carrying 4" is less hose on the ground.
    The only problem is the financial constrants on the department. We have a municiple water supply but only run 3". And, it is set up for only to lay out 1 single line. We have only 1 aux. 2 1/2" pump intake on our trucks. We run 2 engines with pump capacities of 1250 gpm a piece. I am trying to figure out what the best way to increase our water out put with our current resources.

    Most hydrants in our system currently put out 950 gpm. Don't have current pressures with me.

    I know a duel 3" line will get me more water, but do I have to use it in relay.

    Most hydrant lays are about 600'. Some could reach 1000'. What would be oer most pratical way for operation.

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    Quote Originally Posted by osfd399 View Post
    The only problem is the financial constrants on the department. We have a municiple water supply but only run 3". And, it is set up for only to lay out 1 single line. We have only 1 aux. 2 1/2" pump intake on our trucks. We run 2 engines with pump capacities of 1250 gpm a piece. I am trying to figure out what the best way to increase our water out put with our current resources.

    Most hydrants in our system currently put out 950 gpm. Don't have current pressures with me.

    I know a duel 3" line will get me more water, but do I have to use it in relay.

    Most hydrant lays are about 600'. Some could reach 1000'. What would be oer most pratical way for operation.


    You only have one 2.5" intake on your engine?! Ohhh-kay.... well, then I guess you'll need to install a gated (gated, not clappered!) wye on it to use a dual 3" scheme. Maybe MGKREBS can correct me here, but wouldn't the turbulence of water going from 2-to-1 on a wye cause some serious friction loss problems, especially at 900GPM????
    Either that, or get an increaser to go from 2.5" to your steamer intake and run it along with your 2.5" aux intake.

    There actually is a topic going on about this right now, about 2 slots down, it's "3" vs dual 3" vs 4"", you should check that one out for some good info.

    What kind of friction loss per 50' are we looking at?
    At 1000GPM, you're looking at about 60PSI per hundred, so roughly 30PSI per 50' of single 3".

    Best way to operate? Have a rig on the hydrant and relay in if you have much more than 100' of 3" on the ground.
    Last edited by the1141man; 07-29-2007 at 10:52 PM.
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    Red face

    thank you again

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    Would the friction loss decrease if he were to use 100ft sections of 3in, instead of 50ft sections?
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    Quote Originally Posted by BLSboy View Post
    Would the friction loss decrease if he were to use 100ft sections of 3in, instead of 50ft sections?
    Marginally from another pair of couplings eliminated in each 100' section.
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    If you are limited to what you currently have then the smartest thing to do is set the bed up with twin loads of 600 feet each. Having the split bed will allow you to drop single or dual 3" lines. Dropping duals is more sensible in every instance if you arent getting an engine to boost it right away.

    Heres a pic of what someone else suggested you use on your intake...and a picture of a split 3" bed
    Attached Images Attached Images   

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    Quote Originally Posted by the1141man View Post


    You only have one 2.5" intake on your engine?!
    I'll do you one better. We have a single front LDH intake and a single 2 1/2" intake. That's all our old Suppression Chief said we needed.

    Have you thought about using one of these: http://www.akronbrass.com/uploadedFi...ate-Valves.pdf

    If you have a steamer connection on the hydrant and can use that it will provide you with a better flow than two smaller outlets.

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    3" hose has a 750 gpm capacity. Your problem is a lack of 2-1/2 intakes.

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    Quote Originally Posted by allpro View Post
    3" hose has a 750 gpm capacity. Your problem is a lack of 2-1/2 intakes.
    wrong....the capacity is dependent on the length of the lay of hose. It is entirely possible to flow more than 750 gpm through short lays of 3 inch hose.

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    You should seriously consider LDH whether it is 4 or 5 inch. The new 4 inch flows 1000gpm at 12psi FL per 100ft. If your hydrants are low pressure that is the perfect application for LDH.

    If you cannot afford to move to LDH, split your 3 inch bed like MG said and put that other engine you have on the hydrant to boost the pressure.

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    Quote Originally Posted by lexfd5 View Post
    I'll do you one better. We have a single front LDH intake and a single 2 1/2" intake. That's all our old Suppression Chief said we needed.
    What type of pump are you running?

    Not directed at you LExfd5, but it's amazing how poorly trucks can be specced when guys don't understand the limitations or capabilities of pumps, hose and water systems.

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    We are switching from 1 2.5" and 1 3" to 4" this summer with our new engine. We already have one engine with 4" and it seems to be an improvement.although I haven't done math or testing to confirm (which I should, but I just don't have the time right now to do it and it isn't my job anyway). I also like picking up only one hose. If at all possible, I would go 4" over 3".

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    Quote Originally Posted by the1141man View Post


    You only have one 2.5" intake on your engine?!
    Most of our pumpers only have a single "auxillary" 2 1/2" intake as well. Most pumpers have 3 way headers and a 2 1/2" to 5" siamese so even with a single 2 1/2" auxillary intake, we can still take as many as 6 if thats what you really want to do.

    There might be a few engines in the city that have auxillary intakes on both sides.

    My engine is slightly different in that we can take 5" on both sides. So I can only take (3) 2 1/2" lines and a single or dual 5" lines.
    Last edited by MemphisE34a; 05-08-2008 at 09:34 PM.
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    If you're gonna stick with 3", I'd suggest you do your best to make a dual lay. 2 parallel lines have about 1/4 the friction loss of a single line

    In theory, two 3" lines should give you about as much water as a single 4".

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    Quote Originally Posted by txgp17 View Post
    If you're gonna stick with 3", I'd suggest you do your best to make a dual lay. 2 parallel lines have about 1/4 the friction loss of a single line

    In theory, two 3" lines should give you about as much water as a single 4".
    Here's chart from Elkhart detailing the measurements....

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    Quote Originally Posted by FyredUp View Post
    wrong....the capacity is dependent on the length of the lay of hose. It is entirely possible to flow more than 750 gpm through short lays of 3 inch hose.
    Ok, you tell me how much water a 3" line flows?

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    Question Ok...............

    We use "3 for Supply Line. There is some "5 in the County, and if none is coming on the call and we think we'll need it, it's called for. BUT, I get a sense that the Question you're asking is only the tip of the iceberg. You mention Two Pumpers, and specify that there will not be a Pumper on the Hydrant. I then drew the Conclusion that you only run Two rigs, and both are at the Structure that is on Fire. And, that the Two that you have comprise the entire response to a Structure Fire.

    I hope that I am incorrect with my observation, but if I'm right, then a LOT of "Attitude Adjustments" should be made if you want to provide adequate coverage in your district.

    I get Four Engines, Two Ladder Trucks, and a Heavy Rescue, along with some Command Officers and EMS Units, on every structure Fire. This may not be doable in your area, particulary the Ladder Trucks, but you should be able to get more than two Engines. In our case, the Apparatus needed to make up the assignment comes from 4, 5, or 6 stations, and generally speaking, each station is a separate VFD. Our entire County operates like we're one department, instead of 37 different VFDs, all calls are handled by the closest available unit, without regard to any political boundaries. Is it Perfect? No, but almost.
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    osfd399 it has been over 25 years since we ran 2.5" (3" w\2.5" couplings) , but we had started tying directly into the steamer intake with a 6" to female 2.5" and used a standard gate valve to control the intake connection. We had one on each side of the truck and did not use the pre-plumbed 2.5" intake do to friction loss in the plumbing.
    You could also use a 4 Way valve to boost the pressure if the initial line is insufficient.


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    Quote Originally Posted by txgp17 View Post
    If you're gonna stick with 3", I'd suggest you do your best to make a dual lay. 2 parallel lines have about 1/4 the friction loss of a single line

    In theory, two 3" lines should give you about as much water as a single 4".
    txgp17, and others,
    How are your hose beds set up for efficient parallel line deployment?
    Any adapters and/or valves readily accessable?

    Our older main engine is set up with dual 2 1/2" auxillary intake valves, opposite sides.
    Also, 2 large side intakes. Pump side(LH), with butterfly valve, for drafting. Rear large intake with panel area valve. Rear mostly used for dump tank/drafting.

    No LDH for us, yet. Most(all?) surrounding MA dept's have LDH.

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    Quote Originally Posted by dadman View Post
    txgp17, and others,
    How are your hose beds set up for efficient parallel line deployment?

    Both my career and volly FD's formerly ran dual supply line hose beds. Now both run 5 inch with deadlay beds of either 2 1/2 (paid) and 3 inch (volly). When both FD's ran dual lines they were set up to run differently, the career ran reverse lay, the volly forward lay. Both had split beds with 500 each of 2 1/2 on the career FD and 600 feet each of 3 inch on the volly. The career set up had one bed set up as a 2 1/2 inch attack line with nozzle attached and the other went to a gated wye with a bundle of 1 3/4 with a combo nozzle. The volly had both beds set up for forward lay with the adapters attached to the end of one bed needed to connect the two to lay a longer line.

    Any adapters and/or valves readily accessable?

    As above we had them attached to the end of the hose bed on my volly and in the pump operators compartment if my career FD needed to change to a forward lay. Some adapters were carried in the hydrant bag.

    Our older main engine is set up with dual 2 1/2" auxillary intake valves, opposite sides.

    My opinion, do NOT put these lines into the pony (auxilliary) intakes. The friction loss is greater because of the bends in the piping. You are alwaysbetter off to go into the main pump intake. Honestly I would buy a siamese and put it on your steamer connection and put your lines into that.

    Also, 2 large side intakes. Pump side(LH), with butterfly valve, for drafting. Rear large intake with panel area valve. Rear mostly used for dump tank/drafting.

    No LDH for us, yet. Most(all?) surrounding MA dept's have LDH.
    Fact is you have the equipment you have, make it work for you the best you can.

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    FyredUp,
    Thanks for the input. Pun in there somewhere?
    The siamese on the intake you mention, is that the same set-up MG3610 shows with the pic in post #10?
    I don't have the rank or blank checks to make major changes or big purchases. Have to make do.

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