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  1. #1
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    Default Water supply estimates for rural suppression

    I need some help.

    I am looking for some rough guidelines to estimate the amount of water required to suppress structure fires in rural areas. I am the training officer for a department serving a community with zero (0) hydrants. Our suppression activity is supported by water shuttle using our apparatus and through mutual aid. I am looking for some rough guidelines on the amount of water we need for different types of occupancies. I found the calculus equations in technical papers but that really does not help us. I want to offer training to our members on how to establish a sufficient supply of water. How do we know we have enough tankers coming? How many drop tanks do we need? Many of our refill sites are 10-15+ mintues away, one-way. I want to make sure we have a sufficient supply of water on hand in order to ensure the safety of our fire fighters and the effectiveness of our fire ground operations.

    I would like to keep this simple. I remember from my FF1 or 2 class the instructor talking about making rough estimates based on the type of occupancy (single family, 1500 sq ft = roughly xxxxx gallons). But we never covered that information in class.


    Thanks for your help.

    Jon


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    Can't seem to find any hard and fast numbers - these two pages give some idea.

    Apparently, "not very much is needed under ideal conditions". But...when are conditions ever ideal?

    http://www.firefightingwisdom.com/ra...re-fires1.html

    http://en.wikipedia.org/wiki/Firefig..._closed_volume

  3. #3
    Forum Member DeputyMarshal's Avatar
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    You might want to consider rate of flow as important as total water needed.

    The two most common rate of flow formulas are probably:

    Code:
    Area/3=gpm
    
    where area is the square footage
    This works well as a quick estimator for residential structures with typical 8' ceilings.

    Code:
    Volume/100=gpm
    
    where volume is the square footage times ceiling height
    Or you can use this one to adjust for unusual ceiling heights and larger structures. (For small structures, this formula tends to be too conservative, IMHO.)

    A rule of thumb is to be able to deliver that rate for at least 10 minutes.

    So using the first formua for your 1500 sq-ft example, you'd need 1500sq-ft/3= 500gpm x 10 minutes = 5000 gal if the structure is fully involved. If it's just 25% involved, plan to flow at least 125gpm.

    Expect to need more for overhaul.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Default

    If I'm reading your question right, you're looking for a rule of thumb that says if you have a X type of structure then bring Y gallons of water.

    The problem is that fire ground conditions (including structures and fuel loads) are just too dynamic to come up with that rule.

    There is however a rough fire flow calculator that gives a sustained GPM flow required based on the size of the structure and area of involvement.

    The rough flow calculation is area (length X width) / 3 * number of floors = GPM required for fully involved.

    For a 50 X 30 Building - Single floor = thats (50 X 30)/3 * 1 floor = 500 GPM for all area fully involved. 50% involvement = 250 GPM required flow.

    Now using that required flow, the water capacity of your apparatus, and the Full cycle time to haul in a load of water - you can then see what it will take to produce and maintain the required flow.

    You didn't give any apparatus size and load / unload rates so I'll just make up some numbers and you can substitute in your own.

    Assume a Tanker with 3000 Gal tank. Requires 3 minutes to load, 3 minutes to unload, 10 Minutes to water source, 10 minutes to return = a 26 minute cycle time. Thus 3000 Gal / 26 Min = 115 GPM Theoretical delivered fire flow.

    Now we know that in reality you never get the full amount of tank capacity (never totally full, never completely empty) so at best you can round this down to 100 GPM delivered fire flow.


    So back to our Example of a Single Story 50' X 30' building with 50% fire involvement - the required flow was 250 GPM thus you would need 6500 gallons of water on the initial response just to establish / maintain this flow until your first tanker cycled (250 GPM * 26 Minutes) and at least 3 tankers in constant motion to maintain that flow.

    (The question then becomes - Is it really going to require a full 26 minutes of sustained flow to extinguish the fire? Hard to say - again too many variables on fire load, etc but for larger structures - it could very well happen).



    So my suggestions (from many many years in the low man power, rural volunteer world) are:

    1) Have a drop tank (DT) on EVERY apparatus. Your initial unload time will be greater if the Tanker arrives and has to set it's own drop tank. Thus have DT's on the Engines and have them up & ready when the Tankers arrive. Then put down the DT on the tanker for the NEXT tanker to unload in until you have enough tanks on the ground.

    2) Get more water moving on the initial response. You can always send back what you don't need, but if you come up short at the start you won't get caught up till the structure is gone.

    3) Know what your equipment can do. Experiment with your Dept. (and any Mutual Aid Dept.) - try different ways of loading & unloading. Time them to see what's fastest. If you have large gravity dumps, at some point the unloading flow gets to be too low to make the waiting worth the water that's left. (Remember gallons dumped divided by time required to dump it. That last 200 gallons that take forever to unload will greatly reduce the effective GPM delivered by the tanker.



    I know that's probably not the type of answer you're looking for but hopefully it's given you some things to think about and a place to start.

    Kudos to you for taking the proactive approach and trying to "fix" issues before they become issues.
    Last edited by N2DFire; 03-22-2011 at 01:37 PM. Reason: DeputyMarshal replied faster while I was spell checking my epistle ;o)
    Take Care - Stay Safe - God Bless
    Stephen
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  5. #5
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    Default Excellent!

    Thank you gentlemen. This is exactly the type of information I was looking for. I realize every fire is different and we need to respond accordingly. My goal here is to help our members more accurately size-up a structure fire so they can make an timely, effective request for mutual aid. I plan to work on this some more and then make a quick reference sheet which I will laminate and put in each of our apparatus. That way the first responding unit can call in for help while the rest of us are enroute. If this works I will offer it to surrounding departments that call us for mutual aid support so we are all on the same page.

    I really appreciate you sharing your wisdom and experience.

    Jon

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    Quote Originally Posted by N2DFire View Post
    If I'm reading your question right, you're looking for a rule of thumb that says if you have a X type of structure then bring Y gallons of water.

    The problem is that fire ground conditions (including structures and fuel loads) are just too dynamic to come up with that rule.

    There is however a rough fire flow calculator that gives a sustained GPM flow required based on the size of the structure and area of involvement.

    The rough flow calculation is area (length X width) / 3 * number of floors = GPM required for fully involved.

    For a 50 X 30 Building - Single floor = thats (50 X 30)/3 * 1 floor = 500 GPM for all area fully involved. 50% involvement = 250 GPM required flow.

    Now using that required flow, the water capacity of your apparatus, and the Full cycle time to haul in a load of water - you can then see what it will take to produce and maintain the required flow.

    You didn't give any apparatus size and load / unload rates so I'll just make up some numbers and you can substitute in your own.

    Assume a Tanker with 3000 Gal tank. Requires 3 minutes to load, 3 minutes to unload, 10 Minutes to water source, 10 minutes to return = a 26 minute cycle time. Thus 3000 Gal / 26 Min = 115 GPM Theoretical delivered fire flow.

    Now we know that in reality you never get the full amount of tank capacity (never totally full, never completely empty) so at best you can round this down to 100 GPM delivered fire flow.


    So back to our Example of a Single Story 50' X 30' building with 50% fire involvement - the required flow was 250 GPM thus you would need 6500 gallons of water on the initial response just to establish / maintain this flow until your first tanker cycled (250 GPM * 26 Minutes) and at least 3 tankers in constant motion to maintain that flow.

    (The question then becomes - Is it really going to require a full 26 minutes of sustained flow to extinguish the fire? Hard to say - again too many variables on fire load, etc but for larger structures - it could very well happen).
    This is the same formula I use with one exception...plus one. although you have three tankers in cycle and a dumper, it is proactive if not prudent to keep one tender/tanker or heavy gallonage engine in reserve as a back-up water supply. (Huh?) If some form of delay slows the delivery of water, having the secondary or back-up water on scene will give you a tactical cushion to allow for sustained flow or controlled retreat. As a rule, the booster tank on the attack engine should be kept as full as possible for this same reason. The extra tanker or engine of water may be the difference between minor inconvenience or shear panic.
    A coward stands by and watches wrongs committed without saying a word...Any opinions expressed are purely my own and not necessarily reflective of the views of my former departments

  7. #7
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    Default

    Fireeaterbob I think that is a good point and will include in our response planning. I like the idea of being prepared for the unexpected. We service a fairly rural area so the response time for another tanker to respond and help us if we lose a unit from our water shuttle effort would be disasterous.

    Thanks.

    Jon

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    It should go without saying, but we had a problem at a recent barn fire because no water supply officer was appointed. At one point, a drafting fill site that was having prime issues had eight tankers lined up while a fill site running on a municipal hydrant sat idle...

    You need a water supply officer.
    Opinions my own. Standard disclaimers apply.

    Everyone goes home. Safety begins with you.

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    We started using class-A foam years ago, it will stretch your water quite a bit. I would suggest pouring 5 gallons into your first drop tank. If you batch mix it in your apparatus and it sits idle in the tanks for weeks/months some of these foams break down and aren't as effective as a freshly opened can.
    I will point out, don't let using foam factor into not calling for all the tanker support you think you might need.
    There is a lot of info out there for class-A foam, do some reading and learn the benefits of using it.
    Last edited by engineeremtp; 03-22-2011 at 04:30 PM.

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    Quote Originally Posted by engineeremtp View Post
    We started using class-A foam years ago, it will stretch your water quite a bit. I would suggest pouring 5 gallons into your first drop tank. If you batch mix it in your apparatus and it sits idle in the tanks for weeks/months some of these foams break down and aren't as effective as a freshly opened can.
    I will point out, don't let using foam factor into not calling for all the tanker support you think you might need.
    There is a lot of info out there for class-A foam, do some reading and learn the benefits of using it.
    Hmmmmm, never thought of dumpin' in da pond...Our department has issues with anything but an eductor-dont ask, wont tell-This may be my out...gotta try that one in training.
    A coward stands by and watches wrongs committed without saying a word...Any opinions expressed are purely my own and not necessarily reflective of the views of my former departments

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    Quote Originally Posted by tree68 View Post
    It should go without saying, but we had a problem at a recent barn fire because no water supply officer was appointed. At one point, a drafting fill site that was having prime issues had eight tankers lined up while a fill site running on a municipal hydrant sat idle...

    You need a water supply officer.
    You need some common sense as tanker driver. You would think that when the 4th tanker showed up in line he would have been telling someone about it.

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    Quote Originally Posted by engineeremtp View Post
    We started using class-A foam years ago, it will stretch your water quite a bit. I would suggest pouring 5 gallons into your first drop tank. If you batch mix it in your apparatus and it sits idle in the tanks for weeks/months some of these foams break down and aren't as effective as a freshly opened can.
    I will point out, don't let using foam factor into not calling for all the tanker support you think you might need.
    There is a lot of info out there for class-A foam, do some reading and learn the benefits of using it.
    Do flush your pumps with clean water after doing this?

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    Quote Originally Posted by rm1524 View Post
    You need some common sense as tanker driver. You would think that when the 4th tanker showed up in line he would have been telling someone about it.
    Or the person in charge of the fill site.

    It's entirely possible that some of those tanker drivers weren't aware that there wasn't a similar backup at the other site.

    Once somebody figured out that there was a problem, the other site soon had a line waiting - but was filling in about 2-3 minutes per truck vs the 5-7+ at the draft site.

    There were other command issues at the incident - this was just one manifestation.
    Opinions my own. Standard disclaimers apply.

    Everyone goes home. Safety begins with you.

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    Quote Originally Posted by DeputyMarshal View Post
    You might want to consider rate of flow as important as total water needed.

    The two most common rate of flow formulas are probably:

    Code:
    Area/3=gpm
    
    where area is the square footage
    This works well as a quick estimator for residential structures with typical 8' ceilings.

    Code:
    Volume/100=gpm
    
    where volume is the square footage times ceiling height
    Or you can use this one to adjust for unusual ceiling heights and larger structures. (For small structures, this formula tends to be too conservative, IMHO.)

    A rule of thumb is to be able to deliver that rate for at least 10 minutes.

    So using the first formua for your 1500 sq-ft example, you'd need 1500sq-ft/3= 500gpm x 10 minutes = 5000 gal if the structure is fully involved. If it's just 25% involved, plan to flow at least 125gpm.

    Expect to need more for overhaul.
    hey dep, isn't formula # 2 the total gallons to use on indirect attacks?
    Originally Posted by madden01
    "and everyone is encouraged to use Plain, Spelled Out English. I thought this was covered in NIMS training."

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    Quote Originally Posted by tree68 View Post
    Or the person in charge of the fill site.

    It's entirely possible that some of those tanker drivers weren't aware that there wasn't a similar backup at the other site.

    Once somebody figured out that there was a problem, the other site soon had a line waiting - but was filling in about 2-3 minutes per truck vs the 5-7+ at the draft site.

    There were other command issues at the incident - this was just one manifestation.
    Copy the football and the monkey. Better than 95% of the time we are off a hydrant for fill sites. Whenever we have multiple sites we will assign the tankers to a certain site and that is one they go to until we start breaking down fill sites.

    For us the ST in tanker driver calls the fill site either on their way in or when they are getting ready head to the fill site every once in a while the responding chief will call the plug for the tankers. That information is then broadcast to the rest of the tankers responding to the scene. The engineer will also make sure the rest of the tankers know where the fill site is(mutual aid). The engineer will more than likely be the one to start a ND fill site based on volume of fire, gpm's being used, and number of tankers responding or on scene. I guess you could say that our engineer is the water supply officer.

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    Quote Originally Posted by rm1524 View Post
    Do flush your pumps with clean water after doing this?
    Not really necessary. Just expect a little foam to come out of the lines in subsequent use. Class A foam is basically a concentrated detergent, won't harm anything.

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    Quote Originally Posted by engineeremtp View Post
    Not really necessary. Just expect a little foam to come out of the lines in subsequent use. Class A foam is basically a concentrated detergent, won't harm anything.
    See, now, I've always gotten the impression that foam (detergent) in the pump is a bad thing, which is why we usually introduce it into the fire stream after the pump. Detergents and lubricants don't usually do well together.
    Opinions my own. Standard disclaimers apply.

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    Quote Originally Posted by tree68 View Post
    See, now, I've always gotten the impression that foam (detergent) in the pump is a bad thing, which is why we usually introduce it into the fire stream after the pump. Detergents and lubricants don't usually do well together.
    That was my thought as well.

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    Quote Originally Posted by ffmedcbk1 View Post
    hey dep, isn't formula # 2 the total gallons to use on indirect attacks?
    I honestly don't recall seeing it used that way but I won't say it's never been done. I've generally used the Area/3 formula for quick and dirty estimates and the more detailed ISO formulas for more detailed estimates.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by 7Stones View Post
    I need some help.

    I am looking for some rough guidelines to estimate the amount of water required to suppress structure fires in rural areas. I am the training officer for a department serving a community with zero (0) hydrants. Our suppression activity is supported by water shuttle using our apparatus and through mutual aid. I am looking for some rough guidelines on the amount of water we need for different types of occupancies. I found the calculus equations in technical papers but that really does not help us. I want to offer training to our members on how to establish a sufficient supply of water. How do we know we have enough tankers coming? How many drop tanks do we need? Many of our refill sites are 10-15+ mintues away, one-way. I want to make sure we have a sufficient supply of water on hand in order to ensure the safety of our fire fighters and the effectiveness of our fire ground operations.

    I would like to keep this simple. I remember from my FF1 or 2 class the instructor talking about making rough estimates based on the type of occupancy (single family, 1500 sq ft = roughly xxxxx gallons). But we never covered that information in class.


    Thanks for your help.

    Jon
    How many tankers and engines do you have and how many gallons do they carry? Also do you have a draft truck?
    Bring enough hose.

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