Thread: Water supply estimates for rural suppression

1. 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.

Jon

2. 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. 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.

4. 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.

5. 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

6. Originally Posted by N2DFire
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.

7. 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

8. 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.

9. 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.

10. Originally Posted by engineeremtp
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.

11. Originally Posted by tree68
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.

12. Originally Posted by engineeremtp
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?

13. Originally Posted by rm1524
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.

14. Originally Posted by DeputyMarshal
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?

15. Originally Posted by tree68
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.

16. Originally Posted by rm1524
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.

17. Originally Posted by engineeremtp
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.

18. Originally Posted by tree68
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.

19. Originally Posted by ffmedcbk1
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.

20. Originally Posted by 7Stones
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.

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

21. We have two stations with 2 tankers (3,000 and 2,000, both with a/b foam), 2 pumper tankers (2,000 each) and a brush truck (250g). So for our structural fire response we are running 9,000 gallons out the door. We have three top priority mutual aid departments with tankers 2,000+. There is also a CAFS pumper 15 miles away that we will call.

We are a fully volunteer department with 25 members. We usually get 14-16 to respond during a structure fire depending on the day and time. Our coverage area is very remote so it could take us 8-15 minutes from dispatch to get on scene.

Based on some of the calculations given here, I am putting together a simple 3x5 card to place in each of our first-due apparatus (depending on the fire location). This size-up tool will help our members make a quick determination on the amount of water we need in support of our effort and will list our mutual aid options including their anticipated response time. That way we have make some educated decisions when we arrive about how many tankers to request.

I do not want to make this too difficult. The idea is to make it a quick reference so guys who are not used to making mutual aid decisions can feel comfortable calling in support. I like the idea of the "+1" option for tankers to cover any unforeseen problems with our water shuttle situation. That means for 1500 sqft houses 25% and less involved on arrival we will probably call in one tanker in addition to our units. Houses 50% we will request 2 + CAFS, and fully involved structures we will request all three and our CAFS support. There are still too many variables to make this an exact science (type of construction, construction materials/fuel loading, distance and access to water refill [we get 200+ inches of snow], etc. But I think this will work. I will pre-calcuate the GPM and water need for 1000, 1500, 2000, and 3000 sqft structures. We do not have any homes in our area above 3000 sqft. If we run to larger houses which are 50%+ involved we will call additional mutual aid help from our second priority departments early on since their response time will be longer due to distance.

Thank you for all this input. You all have been tremendously helpful.

Jon

22. Why make the guys in the trucks sort it out? Set some parameters - room and contents, bigger, biggest, and preplan what you'll need. Then label the cards "second alarm" and "third alarm" and give the cards to dispatch.

If you break your first due down by sectors the dispatchers won't be looking for the card for "123 Elm Road," only for the sector Elm Road is in.

When you first due apparatus pulls in and decides more resources are needed, he/she simply asks for a second alarm. Same thing if your own department happens to come up short for whatever reason.

Post the extra alarm info in the trucks and with the officers so they can review what's coming.

Get your neighbors to do the same thing and you've got the beginning of a MABAS going.

23. Originally Posted by 7Stones
We have two stations with 2 tankers (3,000 and 2,000, both with a/b foam), 2 pumper tankers (2,000 each) and a brush truck (250g). So for our structural fire response we are running 9,000 gallons out the door. We have three top priority mutual aid departments with tankers 2,000+. There is also a CAFS pumper 15 miles away that we will call.

We are a fully volunteer department with 25 members. We usually get 14-16 to respond during a structure fire depending on the day and time. Our coverage area is very remote so it could take us 8-15 minutes from dispatch to get on scene.

Based on some of the calculations given here, I am putting together a simple 3x5 card to place in each of our first-due apparatus (depending on the fire location). This size-up tool will help our members make a quick determination on the amount of water we need in support of our effort and will list our mutual aid options including their anticipated response time. That way we have make some educated decisions when we arrive about how many tankers to request.

I do not want to make this too difficult. The idea is to make it a quick reference so guys who are not used to making mutual aid decisions can feel comfortable calling in support. I like the idea of the "+1" option for tankers to cover any unforeseen problems with our water shuttle situation. That means for 1500 sqft houses 25% and less involved on arrival we will probably call in one tanker in addition to our units. Houses 50% we will request 2 + CAFS, and fully involved structures we will request all three and our CAFS support. There are still too many variables to make this an exact science (type of construction, construction materials/fuel loading, distance and access to water refill [we get 200+ inches of snow], etc. But I think this will work. I will pre-calcuate the GPM and water need for 1000, 1500, 2000, and 3000 sqft structures. We do not have any homes in our area above 3000 sqft. If we run to larger houses which are 50%+ involved we will call additional mutual aid help from our second priority departments early on since their response time will be longer due to distance.

Thank you for all this input. You all have been tremendously helpful.

Jon
Sounds like a good starting point. You should really look into getting a draft truck. We have one and it can really help water supply issues.
It is a 1 ton 4X4 chevy truck with a 1000 gpm pump mounted in the bed. It has 4 3 inch discharges to fill tenders with.

Good luck

24. The formulas that have been tossed around are from tests performed at Iowa State in the 1960's and are still fairly valid, except for the increased fuel loading caused by the increased use of plastics in furniture. Second number comes from "Hazard classification number" of NFPA. This is an estimator for the total gallons needed for supression. If you scan this you will see that lumber mills have a larger requirement than noncombustable construction, etc. No one on here has mentioned exposures... so for every exposure within 50 feet of the involved building add 1/2 the gpm required by the original fire. The 500 gpm SFD cited would require another 250 for a nearby garage or barn. Incidentally the original Iowa formula was designed to achieve extinguishment in 30 seconds. That is the flow directly applied to the fire, and not wasted running down the outside of the building.

25. Jon,

I put together a couple of tanker shuttle calculators to illustrate the impact of getting tankers on the road sooner rather than later (auto aid instead of mutual aid). The first one is the original one I put together and the second one has a few modifications tailored to the ISO 2 hour water delivery test. These aren't tools you'd use on a fireground, but are useful for pre-planning and illustrating why you need to call for help early.

The tools will output a graph showing how much water you have available on scene throughout the first two hours of an incident. Of course it's all based on "theoretical" numbers and assumes everything goes smoothly, but it's a starting point. The two calculators are the bottom two links here:

Andy

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