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  1. #21
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    Here's another way to look at the concept. Think of your siamese layout. Now eliminate one of the 3" hoses, i.e. hook one 2.5" siamese inlet directly to the hydrant. Now think about this for a minute. Do you think that other 50' of 3" hose around the back of the hydrant into the other port on the siamese is carrying much water? It's not. My suggestion is to further eliminate some restriction and use just a simple 2.5" to LDH increaser on the one side port of the hydrant, and put a gate on other side port for something else should the need arise.

    I saw a photo in one of the magazines of someone doing just this. IIRC they had two LDH suctions, one into each side of an engine or quint, one off the steamer port and one off a side port. They were flowing on a warehouse fire or something. But the point is using the increaser is simple, effective, and it doesn't cost as much as a siamese appliance either.

    Birken


  2. #22
    MembersZone Subscriber mcaldwell's Avatar
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    Quote Originally Posted by Catch22
    I'd like to play with using an 2.5"x5" adapter, or even two sections of 3" siamesed into an additional 5" just to see how much flow we could get out of one.
    I'm with Birk,

    Skip the twin 3" all together, and just use your 2.5" to 4" (or 5") adapter.

    That 3" in even a short 10' configuration is still hugely restrictive compared to the adapter only. You do not need to waste time with the second connection, other than to put on a gate valve for additional units to use.

    Never argue with an Idiot. They drag you down to their level, and then beat you with experience!

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  3. #23
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    First and foremost, with all other conditions being equal, a 4” hose connected to a 4” hydrant outlet will always (I am aware of the danger of using the word “always”) yield a greater flow rate than a 4” hose connected to a 2-½” hydrant outlet.

    Having found some free time, I did some calculations to determine just how much greater the flow rate will be.

    Option A: 4” X 100 ft LDH connected to a 4” hydrant outlet
    Option B: 4” X 100 ft LDH connected to a 2-½” Hydrant outlet using a 2-½” X 4” increaser.
    Option C: Two 3” X 20 ft hose connected to each of the 2-½” hydrant outlets and connected to 4” X 100 ft LDH

    The calculations used 2 water supplies:
    1) Static = 90 psi
    Residual = 60 psi @ 2,000 gpm

    2) Static = 50 psi
    Residual = 20 psi @ 2,000 gpm

    The flow rates at 20 psi available at the end of the 4” X 100 ft of LDH based on each Option and each water supply are:

    Water Supply: 90/60/2,000
    Option A = 1,465 gpm
    Option B = 925 gpm
    Option C = 1,285 gpm

    Water Supply: 50/20/2,000
    Option A = 925 gpm
    Option B = 600 gpm
    Option C = 800 gpm

    The 2 water supplies were used to check for a relatively good water supply and relatively poor water supply. Of course, some are better and some worse. Sorry, I am not going to try every possible water supply scenario.

    Of note is that using both water supplies there is an approximate 54% to 58% increase in flow rate when using a 4” LDH connected to a 4” hydrant outlet versus 4” LDH connected to a 2-½” hydrant outlet. This holds for both water supplies. Whether or not this holds for other water supplies, I don’t know. This, hopefully, answers the original question.

    Oddly, the flow rate from two 3” hoses connected to the 2-½” outlets is greater than that of the 4” LDH connected to a 2-½” outlet.

    Now, in doing the calculations I had to make some assumptions (which I held constant with each Option) and used pressure loss data for a particular hydrant. Other hydrants may change the specific values, but the comparative relationship should remain intact.

    Finally, why is it that so few fire departments have hydrants with two 4” or 4-½” outlets? I know some do and they realize their worth.

  4. #24
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    City of Sacramento has a lot of dual steamers. They also have square operating nuts...? Anyway I think your assumption of dual 20' sections of 3" hose might be a tad unrealistic. Who carries 20' sticks of hose, and is that long enough to loop around the hydrant and any obstructions, into the siamese, without getting kinks? I think 50' sections would be more realistic.

    Birken

  5. #25
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    Dual 3" lines aren't uncommon here, they'll couple any length that you want. Siamese and dual threes are strapped together along with a hydrant wrench as a hydrant pack. Pull the pack, wrap the hydrant and lay away. Here is an example of it in use.
    Attached Images Attached Images  

  6. #26
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    Sure, everyone does that when they don't have LDH but the original question was about running LDH off the side ports. And one LDH will get you a lot more water than 2 3" with a lot less effort expended.

    Birken

  7. #27
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    Quote Originally Posted by BirkenVogt
    Sure, everyone does that when they don't have LDH but the original question was about running LDH off the side ports. And one LDH will get you a lot more water than 2 3" with a lot less effort expended.

    Birken

    Yeah, our is due to the fact that only half of our district has hydrants. The first due engines on the hydranted side have 4" supply while the first due on the non-hydranted side lay dual 3" supply. Thanks for all the information in this thread... especially fireh20... practical examples are just what I needed.

  8. #28
    MembersZone Subscriber Dickey's Avatar
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    Quote Originally Posted by hwoods
    .....we NEVER (Yes, I said Never) connect a Supply Line direct to a hydrant, There is ALWAYS (yes, I said always) an Engine on the hydrant to pump the line.
    Just curious as to why you do this? Not enough hydrant pressure, long hose lays, etc? Do you usually do a forward lay from the hydrant or reverse lays to the hydrant??

    We have the first engine stop at the hydrant, forward lay to the fire. If we know a second engine is right behind the first one, then the second in engine drops the line to the first. Unless it is one of the few bad ones we are aware of, we always have more water than what we need from just static pressure of the hydrant. Maybe we are not using "big water" like you either....don't know.

    Just curious as to how you do it, thats all. not trying to start a schitt storm
    Jason Knecht
    Assistant Chief
    Altoona Fire Dept.
    Altoona, WI

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