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4" vs 5" supply hose, which would you put on your truck?
I recently came in contact with a department that was looking to change from 5" LDH to 4" LDH, I Know that I work for a department that made the change in the opposite direction, saying that the one inch differece, was big to the extent of close to double the friction loss when moving big water. I would like to hear any other feed back from you all, so that when I debate with this desk commander, I can present a good case. I think they main objective is the weight and size of the hose when it is charged, which is in my opinion, most of the time when your needing a supply line its because you have a big enough fire that you need water, why not have alot of water.
Replies to This Discussion
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Permalink Reply by Scott Taylor on
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I think drying hose is tradition left over from the old days when if you didnt dry the cotton jacketed hose, mold became a problem. I havent seen cotton for quite a while.
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Permalink Reply by DAVID GONZALEZ on
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All three of our type 1 engines carry the same size hose 5"-1000, 3"- 800, 2 1/2-500. the only reason is the inlets on our hydrants connect only to 4.5" which is on the 5" supply line. so ask them if the hydrants will be able to adapt to a 4"
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Permalink Reply by Ben Waller on
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The big-city departments that have switched exclusively to 5 inch had members with all of your same arguments, and did the switch anyway - successfully.
Among the other advantages - more room for additional attack hose on the rig, since dual supply beds are no longer necessary.
There's also the issue of using larger-capacity pumps when new apparatus is purchased. The 5-inch gives the capacity to flow what may be required for longer distances with less stress on the vehicles, and it ends up giving the FD more capability for the same amount of effot.
As for no excess capacity for short lays, maybe so, but sooner or later everyone has fires where short lays are not possible.
The basic trade-off between 5-inch and non-LDH is that you are intentionally limiting your single-line flow capacity. It might not hurt you on every fire, but sooner or later, the odds will probably catch up with you.
As for the cars running over the line thing, I've never heard of a single 5-inch hose being run over by a vehicle and being burst. The size of the line - especially if you use the bright yellow hose - visually intimidates most drivers to the point that they won't even consider it.
Vehicles running over 2.5 inch and 3 inch is an age-old, common problem.
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Permalink Reply by capcityff on
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You guys keep bringing up laying duel lines. Who said we lay duel lines all the time. It's VERY rare that we do that. I don't think I've seen it done at all this year.
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What are you talking about? I made no mention of dual anything in that post.
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Permalink Reply by Eat The Roof on
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Ben,
I suggest you read this excellent article I just happened to come across by Capt. Bill Gustin of the Miami Dade Fire Dept.- Does a great job of describing both the benefits and limitations of LDH
http://www.fireengineering.com/articles/print/volume-153/issue-1/fe...
The big-city departments that have switched exclusively to 5 inch had members with all of your same arguments, and did the switch anyway - successfully.
I would be glad to see the link to such a discussion.I am guessing the "successful" part depends on who you talk to.If tomorrow I went into work and was told, that from now on we will be using only LDH.I would make it work but that does not mean I would consider it a success.
As for the cars running over the line thing, I've never heard of a single 5-inch hose being run over by a vehicle and being burst.
That doesn't mean it doesn't happen(see article)
The size of the line - especially if you use the bright yellow hose - visually intimidates most drivers to the point that they won't even consider it.
Then you must operate in an area where people exercise judgement,restraint and make informed decisions.That unfortunately is not a particular strength of my first due area.
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Quote: "It will supply more than two 2.5-inch or 3 inch lines."
It's actually been mentioned several times by a bunch of you.
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The reason I questioned you responding to the dual line thing was this in the post to which you responded;
"The basic trade-off between 5-inch and non-LDH is that you are intentionally limiting your single-line flow capacity. It might not hurt you on every fire, but sooner or later, the odds will probably catch up with you."
Given that I was specifically discussing single non-LDH in that post, that's why I questioned your bringing dual supply lines up here.
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A couple of other thoughts on this...
If the 2nd due rig backs down and reverse lays, it would seem that rig would block the street more than any hose selection. If that is the case, then no civilian vehicles will be able to get into the street to run over hose, regardless of what size is laid.
Another point about the water volume is that it gives you way to protect a larger margin of error. If you get a wind-driven fire, forcible entry problems, the need for exposure protection while changing from Offensive do Defensive mode, an unexpected gas-fed fire problem, or something else that increases the fire size or the number of exposure problems, then you're better prepared to handle it with the water already in front of the fire.
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Permalink Reply by FETC on
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Guys this topic is specific to the jurisdictions required NEED. Big city guys flow alot of water, often only have to use a short whip or two to the nearest good hydrant. (Most rural guys are like whats a whip?) And then most big city guys are not familiar with rural water supply, drafting from a pond or river and using a hose reel truck that can lay down 5000' of LDH. In these jurisdictional requirements, the friction loss between 3", 4" and 5" is dramatic and achieved flows are different over a long distance. We have been doing dual 4" lays in certain target hazard districts to achieve big water. Many are arguing that their opinion is correct. Single 3", dual 3" lines with a good system will flow alot sh*t load of water. 4" and 5" are good as well...
The answer to this thread is whatever size LDH that provides your engineer the required flow for successful extinguishment.
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Permalink Reply by Don Catenacci on
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While it is apparent that many cities may flow adequate amounts of water through single, or dual, 3 inch lines it simply cannot be disputed that 5 inch hose will out flow the 3 inch no matter what the length of the lay is, or the capabilities of the hydrant.
The one factor that seems to be left out of the equation is staffing. Milwaukee and DC have been used as examples of FDs that utilize 3 inch hose. The one advantage they may have over smaller cities, or suburban/rural FDs, is staffing and amount of apparatus. If either of those FDs lay in a single 3 inch line and find themselves overwhelmed they can have MULTIPLE additional companies lay in supply lines and bolster the incoming water. Not many smaller FDs have that IMMEDIATE resource so they set up for maximum flow off from that first arriving pumping apparatus. The simple way to do that is to lay LDH and 5 inch is the best choice for that.
I am not at all saying Milwaukee or DC or anyone else that uses 3 inch should change to 5 inch. What I am saying is they have additional resouces that can immediately be called on to fix their water supply issues so they can play the odds of smaller lines that may work for the majority of their calls.
Frankly, I can't for the life of me see why anyone buys 4 inch hose. At least not for supply. The friction loss and capabilities of 5 inch is far superior to 4 inch. Friction loss in 4 inch is 2 1/2 times that of 5 inch. But then again 3 inch is 4 times 4 inch and 10 times that of 5 inch.
Let me repeat this, and I will type SLOWLY so I m not misunderstood. I am not telling ANYONE to change what they do. If it successful for them then who am I to tell them to change what they do. We do what we do because it works for us, and it is really that simple.
Honestly, I think, for the most part, this has been a very good discussion.
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Good points Don. We operate with 10 guys on duty in a small city. There is no other companies to bolster the GPM demand. (at least not for a while) I love going to NFA and talking strategy and tactics with urban guys.
As for why would anyone buy 4" - from our standpoint to remove and replace 12 thousand feet of it would be a little costly. Especially seeing laying dual 4" lines has yet to be overrun by flow demands.
If I were in a brand new department that was buying everything from scratch, it would be an easy decision for buying 5" LDH.
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