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Thread: Hydrant outlet Q

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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

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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.

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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
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    Quote Originally Posted by Firetacoma1 View Post
    We had hydrant training last night and it made me wonder something... one of the teams instead of using the 4" output on the hydrant, used an adapter to hook the 4" supply line to a 2.5" discharge. What's the difference in flow between the 2... I argued that even with a 4" line, you're restriced by the 2.5 inch orifice of the hydrant... a bunch of the physics and engineer types thought it was neglible... I quickly shut up, but wondering if they're right?

    What's the flow with a 2.5" hydrant output adapted to flow through 4" hose?
    What's the flow with a 4" hydrant output to flow through 4" hose?
    The flow from the 4" will be 2.56 times greater than the 2.5", which is pretty significant. The outlet restricts the flow, even with LDH on it. You may not need that much water, but nobody ever got hurt because they had too much water available.

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    Interesting question and thank you. If memory serves, (always suspect) the friction loss of the 2.5 inch outlet from the barrel of the plug would be very little. You most likely would get at least 90% and perhaps a whole lot more. Perhaps even 98%? The 2.5 inch SIDE outlet discharge would flow just about as much as the 4 inch outlet.

    The GPM of the 4 inch hydrant outlet using a 4 inch hose would be dicated by the flow of the hydrant unless the plug flow is high enough that friction loss would instead dicate max flow through that 4" hose. Then that high GPM flow/pressure would; Edit; BE determined by the friction loss per 100 feet of flow going through the aforementioned 4 inch hose.

    But ... and this may not apply here, if that 2.5 inch outlet is a "warf valve" or "corporation value" and is on top of the barrel, then the construction and type of that special case low flow outlet might directly and greatly restrict that 4 inch hose flow. Our wet type Class 1 Edit; or Class A West coast plugs had two 4" NS outlets on big mains and one 4" and 1 2.5" NS on most.

    Hope this helps. Long ago and far away. Respectfully to all. HB of CJ (old coot) retarded EN
    Last edited by HBofCJ; 04-02-2015 at 01:39 PM.

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    Quote Originally Posted by HBofCJ View Post
    Interesting question and thank you. If memory serves, (always suspect) the friction loss of the 2.5 inch outlet from the barrel of the plug would be very little. You most likely would get at least 90% and perhaps a whole lot more. Perhaps even 98%? The 2.5 inch SIDE outlet discharge would flow just about as much as the 4 inch outlet.

    The GPM of the 4 inch hydrant outlet using a 4 inch hose would be dicated by the flow of the hydrant unless the plug flow is high enough that friction loss would instead dicate max flow through that 4" hose. Then that high GPM flow/pressure would determined by the friction loss per 100 feet of flow going through the aforementioned 4 inch hose.

    But ... and this may not apply here, if that 2.5 inch outlet is a "warf valve" or "corporation value" and is on top of the barrel, then the construction and type of that special case low flow outlet might directly and greatly restrict that 4 inch hose flow. Our wet type Class 1 West coast plugs had two 4" NS outlets on big mains and one 4" and 1 2.5" NS on most.

    Hope this helps. Long ago and far away. Respectfully to all. HB of CJ (old coot) retarded EN
    HOLY CRAP! Finally something we can agree on!
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    Quote Originally Posted by HBofCJ View Post
    Interesting question and thank you. If memory serves, (always suspect) the friction loss of the 2.5 inch outlet from the barrel of the plug would be very little. You most likely would get at least 90% and perhaps a whole lot more. Perhaps even 98%? The 2.5 inch SIDE outlet discharge would flow just about as much as the 4 inch outlet.

    The GPM of the 4 inch hydrant outlet using a 4 inch hose would be dicated by the flow of the hydrant unless the plug flow is high enough that friction loss would instead dicate max flow through that 4" hose. Then that high GPM flow/pressure would determined by the friction loss per 100 feet of flow going through the aforementioned 4 inch hose.

    But ... and this may not apply here, if that 2.5 inch outlet is a "warf valve" or "corporation value" and is on top of the barrel, then the construction and type of that special case low flow outlet might directly and greatly restrict that 4 inch hose flow. Our wet type Class 1 West coast plugs had two 4" NS outlets on big mains and one 4" and 1 2.5" NS on most.

    Hope this helps. Long ago and far away. Respectfully to all. HB of CJ (old coot) retarded EN
    I'm confused. Are you saying that the 2 1/2" and the 4" outlet on the same hydrant are going to flow the same amount of water?

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    Quote Originally Posted by micahma View Post
    The flow from the 4" will be 2.56 times greater than the 2.5", which is pretty significant. The outlet restricts the flow, even with LDH on it. You may not need that much water, but nobody ever got hurt because they had too much water available.
    It's been nine years but I think you finally gave the OP a good answer. A very simple answer to his very simple original question.

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    Quote Originally Posted by captnjak View Post
    It's been nine years but I think you finally gave the OP a good answer. A very simple answer to his very simple original question.
    The difference is the restriction on a 2 1/2 discharge is minimal due to the length on the outlet. It is entirely possible with a hydrant discharge pressure of 20psi to get over 800 gpm out of a 2 1/2 inch discharge, over 1300 gpm at 50psi, and over 1600 gpm at 80psi. Of course this is all dependent on what the total flow the hydrant is capable of. It may not be equal to a 4inch discharge, or in our case a 4 1/2 inch discharge, but most of the time it is more than enough water if for some reason you can't make the steamer.

    So technically 2.56 is correct, but without knowing the hydrant flow capability it really doesn't mean anything of useful value.
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    Quote Originally Posted by FyredUp View Post
    The difference is the restriction on a 2 1/2 discharge is minimal due to the length on the outlet. It is entirely possible with a hydrant discharge pressure of 20psi to get over 800 gpm out of a 2 1/2 inch discharge, over 1300 gpm at 50psi, and over 1600 gpm at 80psi. Of course this is all dependent on what the total flow the hydrant is capable of. It may not be equal to a 4inch discharge, or in our case a 4 1/2 inch discharge, but most of the time it is more than enough water if for some reason you can't make the steamer.

    So technically 2.56 is correct, but without knowing the hydrant flow capability it really doesn't mean anything of useful value.
    I get your point and I agree.

    Another member (old coot) seemed to imply that the flows would be nearly identical. That I do not get.

    The Op basically asked if the difference between the flow of a 4" hose on a 4" hydrant outlet and a 4" hose on a 2 1/2" hydrant outlet would be negligible. He stated that the engineer types suggested it was negligible. I submit that the difference would not be negligible. He was indeed asking for actual volume numbers, which we can't give him. Although a lot of people tried and did so using hypothetical numbers. I kind of zoned out reading the responses because I'm not a big hydraulics guy. I'm just gonna stick with the difference being substantial, at least in all likelihood.

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    Quote Originally Posted by captnjak View Post
    I get your point and I agree.

    Another member (old coot) seemed to imply that the flows would be nearly identical. That I do not get.

    The Op basically asked if the difference between the flow of a 4" hose on a 4" hydrant outlet and a 4" hose on a 2 1/2" hydrant outlet would be negligible. He stated that the engineer types suggested it was negligible. I submit that the difference would not be negligible. He was indeed asking for actual volume numbers, which we can't give him. Although a lot of people tried and did so using hypothetical numbers. I kind of zoned out reading the responses because I'm not a big hydraulics guy. I'm just gonna stick with the difference being substantial, at least in all likelihood.
    Substantial to the capabilities of the hydrant, most often inconsequential to necessary fire flow for most incidents.
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    Quote Originally Posted by FyredUp View Post
    Substantial to the capabilities of the hydrant, most often inconsequential to necessary fire flow for most incidents.
    Yes, I've already said I agree with that.

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    Quote Originally Posted by captnjak View Post
    Yes, I've already said I agree with that.
    HOORAY!! We agree again!! LOL
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    Quote Originally Posted by Firetacoma1 View Post
    We had hydrant training last night and it made me wonder something... one of the teams instead of using the 4" output on the hydrant, used an adapter to hook the 4" supply line to a 2.5" discharge. What's the difference in flow between the 2... I argued that even with a 4" line, you're restriced by the 2.5 inch orifice of the hydrant... a bunch of the physics and engineer types thought it was neglible... I quickly shut up, but wondering if they're right?

    What's the flow with a 2.5" hydrant output adapted to flow through 4" hose?
    What's the flow with a 4" hydrant output to flow through 4" hose?
    Why wouldn't you go with the least restriction is what I'm thinking. I see no reason at all to go with the smaller opening. Of course around here almost nobody has 4", it's all 5"...

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    Quote Originally Posted by johnsb View Post
    Why wouldn't you go with the least restriction is what I'm thinking. I see no reason at all to go with the smaller opening. Of course around here almost nobody has 4", it's all 5"...
    September, couple years ago, we were mutual aid to a very large boardwalk fire. Not an area we respond mutual aid to but this was a different fire for the area. Found the hydrant to have a 3 1/2" steamer connection. We don't carry a 3 1/2" adapter, so had to use both 2 1/2" outlets.
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

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    Quote Originally Posted by johnsb View Post
    Why wouldn't you go with the least restriction is what I'm thinking. I see no reason at all to go with the smaller opening. Of course around here almost nobody has 4", it's all 5"...
    If the hydrant steamer discharge is a different size than you carry, or simply the cap won't come off, it may make using the 2 1/2 inch discharges your only choice.
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    While not exactly the yes or no answers the OP was looking for, a lot of decent discussion can be had on this topic. It's amazing how little understanding of hydraulics a large number of firefighters have. I find I'm still learning, many years since my April 1986 acceptance to the local VFD. Many of us know what we use, often not even knowing why, this is a pretty decent topic that illustrates this.

    To that point I will offer that if some would recall the GPM flow available via certain tip sizes, they'd quickly agree that a 2 1/2" port is capable of far greater flow than 2.5" hose, so when you're in a pinch (rarely a first choice) a 2.5" to LDH adapter can give you pretty decent flow. No matter what port you use, the available water will be a factor, knowing what variables affect this is important for pump operators.

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    Quote Originally Posted by FyredUp View Post
    If the hydrant steamer discharge is a different size than you carry, or simply the cap won't come off, it may make using the 2 1/2 inch discharges your only choice.
    Obviously if there's only one size outlet available, you don't have a choice...

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    Excellent question captnjak and thank you. The flow between the 2.5 inch and 4.0 inch outlets on the barrel of the plug with Class A or Class 1 type plug construction would be very close to the same. At least 90%. Maybe much more. The restriction of the 2.5 inch outlet does not enter that much into the plug flow. In addition, when you add in any decent length of LDH supply line flowing from that aforementioned plug at hydrant provided pressure, then it enters into it even less.

    Practically speaking, the supply line pressure difference would be very slight, if any, as felt/observed by the Engineer at the pump panel. And when that LDH is supplying just about all it can from that plug at plug pressure, the difference is non detectable. At that point you would need to pump that supply LDH to get the required or needed GPM. But ... I do not know about other types of plugs, like East Coast wet barrels or Type/Class 2 or B. Hope this helps. HB of CJ (old coot) ex EN.

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    Quote Originally Posted by HBofCJ View Post
    Excellent question captnjak and thank you. The flow between the 2.5 inch and 4.0 inch outlets on the barrel of the plug with Class A or Class 1 type plug construction would be very close to the same. At least 90%. Maybe much more. The restriction of the 2.5 inch outlet does not enter that much into the plug flow. In addition, when you add in any decent length of LDH supply line flowing from that aforementioned plug at hydrant provided pressure, then it enters into it even less.

    Practically speaking, the supply line pressure difference would be very slight, if any, as felt/observed by the Engineer at the pump panel. And when that LDH is supplying just about all it can from that plug at plug pressure, the difference is non detectable. At that point you would need to pump that supply LDH to get the required or needed GPM. But ... I do not know about other types of plugs, like East Coast wet barrels or Type/Class 2 or B. Hope this helps. HB of CJ (old coot) ex EN.
    I'm having a hard time with the idea that the 2 1/2" outlet will give "much more than 90%" of what the 4"outlet will give. Take the hose out of the question. Take the pump operator out. Take the pressure out. The smaller opening should give less water, no?
    Unless the 4" outlet is overkill from the start and is not delivering the amount of water it is capable of due to lower flow in the system itself.
    Sorry but I'm still confused.

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    Here's a spec sheet from Elkhart Brass. Disclaimer: This does not constitute an endorsement.

    At 20 PSI, the chart shows a 750 GPM flow for a 2.5" butt.

    At the same pressure, a 4.5" butt will flow 2430 GPM.

    Of course, this assumes that such a flow is available at that hydrant. With a small main, or low residual pressure, the flow will obviously be less (as will the residual pressure at higher flows).

    One question that factors in is the expected flow, for firefighting purposes.

    If the 2.5" butt with 20 PSI can flow 750 GPM, and the needed flow is less (say, 2 or 3 1.75" lines), then that 2.5" butt can certainly supply all the water you ask of it, assuming minimal friction loss (as LDH would provide). I'd opine that such a situation covers 90% of our firefighting situations, which is why folks might feel that hitting the 2.5" butt will be sufficient. It may very well be!

    If, however, you're asking that hydrant/2.5" butt to supply a deck gun with a 2" tip, you're going to fall short and start collapsing the LDH (if you're pumping it).

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    Even with everything else taken out of the equation, a 2.5 inch outlet flow on our type of plugs would be nearly that as a 4 inch outlet. Again, if memory serves, (ancient history) when we would yearly flow all of our plugs, both the 4 inch and 2.5 inch outlets were tested. The flows recorded with a pilot (sp?) gage were nearly the same. At least in our case, it did not make that much difference.

    Again, with all the other stuff added or subtracted or divided in like hose stretches, plug pressure, gpm flow, etc.., it gets diluted even more. Practically speaking, no real difference. The interior configeration and construction of our plugs let the water flow nearly as much ill regardless of which port you were using. Again, a West Coast wet barrel type A or type 1 plug. Hope this helps. HB of CJ (old coot) ex EN

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    Quote Originally Posted by HBofCJ View Post
    Even with everything else taken out of the equation, a 2.5 inch outlet flow on our type of plugs would be nearly that as a 4 inch outlet. Again, if memory serves, (ancient history) when we would yearly flow all of our plugs, both the 4 inch and 2.5 inch outlets were tested. The flows recorded with a pilot (sp?) gage were nearly the same. At least in our case, it did not make that much difference.

    Again, with all the other stuff added or subtracted or divided in like hose stretches, plug pressure, gpm flow, etc.., it gets diluted even more. Practically speaking, no real difference. The interior configeration and construction of our plugs let the water flow nearly as much ill regardless of which port you were using. Again, a West Coast wet barrel type A or type 1 plug. Hope this helps. HB of CJ (old coot) ex EN
    It appears that you are discussing pressure at the hydrant whereas I'm discussing volume. Unless I'm wrong about pitot gauges being used to test pressure.

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    Pitot gage, not pilot gage. Thank you. I also assumed, (again a dangerous word) that we are on the same page regarding West Coast wet barrel plugs. The barrel is well, like an upright barrel. The various sized outlets are on the sides. Each outlet has its own stem. Horizional. (sp) Each outlet has its own shutoff.

    There is NOT just one stem on the top of the plug opening up everything. You can run a 4" outlet and later if necessary run an additional 2.5" hose into the 2.5" outlet without bothering or shutting down the 4" outlet. They are separate. The insides of the plugs are almost the same with either the 4.0" outlet or the 2.5 inch outlet.

    Hope this helps. Respectfully. Our situation with the nearly identical flows with either a 4" or 2.5" outlet may just be a West Coast thing ... only. Again, wet barrel plugs. HB of CJ (old coot) Speeel chzk not working. Something to do with this Forum format and Lenix Mint 17 Firefox Mozilla not being compatible. Yikes!

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