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We would be delighted to try and obtain an answer to any questions you might have regarding fire hydrants, whether of a technical or general nature. Below are recent questions and answers from the FireHydrant.org mailbag. If you have a question, Email Us. |
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#31 - I am working on fire protection system design for a Power Project in Ohio state. We have about 14 Yard Hydrants Class-I and 6 no. Class -II internal fire hydrants. Apart from this we have only one dry type spray system for lube oil tank, the water requirement for the same is 100 gpm. Please advice me on the criteria used for sizing (capacity) the fire pumps and fire mains. All the internal hydrants are in one Building. The fire flow requirements, quantity of water in gallons per minute at 20 lbs. p.s.i. (pounds per square inch) will be be determined by the insurance rating association which establishes a protection rate or class for the power plant (risk). This will be done by the 'improved risk department' of the regional 'Insurance Rating Organization' (ISO) office or the Factory Mutual Insurance Organization. You should consult these groups before designing any hydrant, water main layout etc. These requirements are very important in the selection design of a fire pump (pump characteristic curve). Perhaps you don't have enough fire flow at the risk now and a more thoughtful examination is necessary.
Joseph A. O'Keefe, PE |
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#32 - Hello, I am the Chief of a volunteer department in Pennsylvania. The water authority is installing a new ten inch water main to a industrial park that is presently not served with water. The new section of line will run approximately 2.5 miles through land that is presently farmland but is zoned for industrial use. My question is this. Where can I get supporting documentation as to hydrant spacing along this line? I have been through NFPA standards and I cannot find any standard that spells out any minimum spacing standards. I need this information urgently for the decision on where and how many hydrants will be made using a cost basis rather than public safety. The actual statutory requirements for fire hydrants vary from state to state. Some states have adopted the Uniform Fire Code, some have adopted a locally amended version of the UFC, and some have not adopted the code. The Insurance Services Office (ISO) apply NFPA standards as well as the Uniform Fire Code when scoring local jurisdictions for establishing an agency's insurance protection class. Therefore as a practical matter, these are the guidelines that should be followed. NFPA has published a table of distances. This table actually varies according to the hose loads carried by the local fire agency and falls into two general categories. If your apparatus carries large diameter hose (4" or greater), the maximum distance from any fire hydrant to a protected structure shall not exceed the SHORTEST hose load of any of your designated in-service fire engines. (Reserve apparatus or special apparatus that do not ordinarily respond on a first alarm assignment as a pumping engine and that do not ordinarily carry full LDH loads, are usually exempted.) Under ordinary circumstances the distance from hydrant to structure is measured to a functional location proximate to the building. In other words, if an engine would take a position in the street front of a structure that is set back 100 ft from the roadway, than the ISO inspector will usually measure from the hydrant to a reasonable point on the frontage. The additional distance ordinarily covered by attack lines would not be counted. So if your shortest LDH hose load is 900 ft, then hydrants should be installed within 900 ft of all anticipated parcels with structures. If you do not carry LDH on all of your first alarm engines, the Table of Distances starts discounting credit for all structures beyond 500 ft. of any hydrant and this discount increases with distance. Another issue is total fire flow. A particular structure may require flows greater than one hydrant can provide. You can only get credit for flows from additional hydrants that are within the Table of Distances. As a result of these and other practical issues, the prevailing spacing for fire hydrants is every 500 ft. alongside a public roadway, with additional hydrants installed as needed to serve structures that have significant setbacks from the public roadway and where engines would likely take positions in parking lots or private driveways. (These additional hydrants are typically the responsibility of the party who develops the parcel.) While the agency I work for is in an urban environment, I live in a rural area with limited financial resources. We received a water system improvement grant to add water mains, but did not receive funds for fire hydrants. We mapped where hydrants whould eventually be located and had taps and hydrant laterals installed at the time the water mains were put in. Then over successive years we were able to purchase hydrants and buries which we then had installed on the existing hydrant laterals. This approach significantly reduced our fire agency costs since we didn't have expenses associated with sawing up the roadway, trenching and repaving when the hydrants were installed. The way I would probably approach your situation is this: 1. I would place hydrants on a map, targeting hydrants at corners of principle intersections and filling in between them at approximately 500 ft intervals. Logically I would seek to have the water agency provide the total installations. If they balk, perhaps the industrial park developer could be leaned on to add a few off-site fire hydrants in mitigation for the increased risk and need for emergency services that the development would bring with it. 2. If they won't go for a full set of hydrants, my Plan 2 would involve getting hydrants installed at principle intersections and "blind" taps at the other hydrant locations. 3. My "last ditch" plan would involve getting at least the hydrant taps installed, citing cost effectiveness, minimal future disturbance of the roadway surface (get the public works superintendent on your side for that argument), and reduced long term maintenance costs since the hydrant laterals will be set on cast "Tees" as opposed the mains being bored and saddle clamp taps installed. 4. Part of my justification arguments would include: Good luck with this project. Please let me know if I can be of further assistance. ":O) Willis Lamm, Water Supply Officer |
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#33 - Good Morning, I am in a debate with my village fathers. we currently have proposed a new construction of a plumbing storage facility along with a auto repair shop. The closest hydrant is approx 1000 feet. I am insisting on a hydrant within 500 feet of the structure. I have been asked to submit law or regulation supporting my 500' order. Unfortunately I have been unable to do so, either by NYS uniform code or NFPA. If I am unable to find information the project will go forward putting firefighters in jeopardy. If you can forward any information you have it would be appreciated The appropriate reference in your situation would be the Uniform Fire Code and the NFPA "Table of Distances" in the water supply section. The Uniform Fire Code gives authority to to the Fire Chief with respect to number, type and placement of fire hydrants. The NFPA Table of Distances provides rules with respect to the flow credit given to hydrants that are placed various distances from the structure being considered. Whether of not your state or local government has adopted the Uniform Fire Code or recognizes the NFPA standards, they have an impact on your community's fire insurance rating. When your jurisdiction is inspected by the Insurance Services Office, the inspector will use current regulations and standards as a basis for your rating. Ignoring the standards when new development takes place will have a cumulative adverse impact on your community's fire insurance premiums, and in some situations can contribute to some liability on the part of the local government agency. So as a matter of responsibility, every jurisdiction needs to follow modern standards and regulations. As a practical matter, the following design process is commonly followed. 1. Establish the fire flow of the new structure. NFPA provides formulas, however the building architect or the fire prevention bureau of a nearby large fire department should be able to calculate fire flow for your situation based on square footage, hazard factor, building construction, separation distance between buildings and other relevant points. 2. Establish the fire flow available on the public water main. If the available fire flow meets or exceeds the required fire flow, construction mitigation (fire sprinklers, increased fire resistance, etc.) may not be necessary. 3. Establish fire flow that would be credited to the existing hydrant based on the NFPA Table of Distances and the nozzle configuration of the hydrant. 4. Determine if any flow credit deficiencies exist and base new hydrant requirements on what additional hydrants would be necessary to meet the required fire flows. If for example the nearest fire hydrant is 900 feet away and the required fire flow is 1250 GPM, the hydrant may be only credited 600 GPM due to the distance. Thus the development would be charged a 52% fire flow deficiency. The most cost-efficient mitigation of a fire flow deficiency usually involves installing one or more properly configured fire hydrants within a proper distance from the proposed structures at location(s) specified by the Fire Chief. The number of additional hydrants needed would be dependent upon the actual required fire flows and any limits that would be imposed on the placement of the additional hydrants such as whether the hydrants would be credited their full available flow or limited flow based on the Table of Distances. RULE OF THUMB: Apart from special issues relating to unusually large or hazardous structures, or structures that have significant setback from the roadway (which would require additional hydrants to be placed on private property), the most commonly used "rule of thumb for installing fire hydrants is to place hydrants designed with at least one pumper (4" or 4½") outlet every 500 Ft. This rule provides uniform and consistent connectivity for fire department forces and covers most of the distance issues that may arise, particularly in commercial zones where as is likely that structures there would require fire flows that may have to be provided by more than one hydrant. A feature that illustrates much of this information can be viewed at http://www.firehydrant.org/info/design01.html Best regards, Willis Lamm, Water Supply Officer |
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#34 - We live on a flat street. The fire hydrant is approximately 63 feet from our house. For one solid week our water pressure at the house has gone down a lot. The water company put a computerized meter on our house to test the pressure in any given 24 hours. The pressure ranges from just under 40psi to as high as 80 psi (which is where we used to be). The fire hydrant was tested and it too was exactly the same as our house. They say their two wells are fully charged. They can't find any leaks. What PSI IS REQUIRED FOR FIRE SAFETY? AND THANK YOU. Quantity of water available for fire protection (engine company supply) is the difference between the static pressure and residual pressure computed to the minimum necessary at 20 p.s.i. Static pressure is the 'dynamic water head' from water reservoir or standpipe. Pumps may be used but failure of electrical supply may be a problem if no diesel or gas turbine backup. Without water in a reservoir or standpipe the pumps would be running constantly. The local water company probably has a reservoir or standpipe providing a steady static pressure and reliable supply. In either case, static pressure is the 'head of water' available between the difference in the overflow at the reservoir or standpipe and the elevation of the hydrant near your home.This head of water is calculated in 'feet' which is converted to pounds per square inch (p.s.i.). When the hydrant is opened for supply to a pumper (engine) at a fire, the pressure remaining is called 'residual pressure' and this is the available pressure minus the friction loss from the reservoir or standpipe or pump, minus consumption. The only true way to determine the quantity of water available is to conduct a fire flow test on the hydrant or have the water company use a computer model to calculate the amount of pressure (p.s.i. and quantity gallons per minute (g.p.m.) available for engine company supply. A main line water main gate valve may be shut. The average static pressure in pounds per square inch oftentimes is between 60-85 p.s.i.; however I have encountered static pressures of 40 p.s.i. and when the 4 1/2 inch engine (steamer) connection is opened the pressure doesn't fall 1 pound. For example I believe the Chicago Ill water system has low static pressure but has adequate fire flow. The local water company or municipal water authority is the most reliable point of information for you. If they report adequate fire flow is available for the structural conditions around you home they may be right. Your local fire department is also a reliable source of info. Years ago fire departments would run hydrants lines directly from a hydrant to the fire scene; however most departments now position a pumper (engine) at the hydrant and pump to another pumper at the scene of the fire through large diameter (4-inch)hose. The engine company at the fire scene then becomes the 'hydrant'. There are more 2 l/2 inch outlets on a pumper than on a typical fire hydrant. When 2 1/2 hose lines from fire hydrants in the past depended on static pressure with no pump supply static pressure was a factor. Joseph A. O'Keefe, PE --- Those involved in fire protection are far more concerned with flow and the availability of water more so than pressure. They have pumper trucks to take care of that. Any flow testing I have seen is based upon theoretical calculations which project flow in GPM @ 20PSI, so I would presume that this is what is deemed the minimum for fire protection. John Clack --- I agree with the answers I have seen so far. Static pressure at the hydrant or your house has little to do with how adequate the fire protection is. During peak demand times, it is not unusual to see static pressures fluctuate. We require that hydrants have the capacity for a minimum flow of 1,000 gallons per minute at 20 p.s.i. We have several above ground tanks, and booster stations that are capable of boosting the pressures and flows quite considerable during a fire. What most folks do not realize is that pressure is a constant, but flow is not. Whether the pipe is 3/4" of an inch in size or is a 12" main, the pressure when taken on a relatively closed system will be about the same. what will change is flow. If you have a crimp in your service line, or a small blockage, I can check the pressure, and it will appear ok, but when I open the faucet, I get a strong surge at first, but then it dies down. That is low or restricted flow. To answer your question [in] short, I would not be concerned about pressure drops in an overall system, if this is the norm, and it has always been that way. However, if your pressure is always at 60-80 p.s.i., and never dropped until recently, then something has changed. I'd have your Utility keep [looking] for any recent changes in the system to possibly have caused the problem. If you have a pressure reducing valve on your side of the line, you may check it, as it can fluctuate and cause the same problem." Pennie Simmons |
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#35 - We live in a rural community with water supplied by a city water works, we have had fire hyds in our community for years accepted by ISO, the city is now calling them flush hydrants and says we can not use them for fire suppression. Without these hydrants our ISO rating will change, what can we do ? First you need to determine the laws in your state. Can a water agency legally refuse to provide water for fire suppression? In many states it can't. Secondly you need to determine the contract or agreement between the City and County (or special district) for rural water supply. If the contract does not specifically disallow use for fire protection, you have an equal protection argument. In other words, unless there is something specifically agreed to the contrary, all the rate payers, users, etc., should expect the same service and protection as the people in town. If in the past the City has provided water for fire protection either actively or passively (they didn't object) the fire district attorney should send them a notice of liability if they issue orders to prohibit taking water for fire suppression. Then there is the common sense issue. Unless there is a technical reason not to use hydrants for fire suppression (e.g., it would cause unreasonable damage to the system) then to deny reasonable and customary usage of these fire hydrants could be considered an unreasonable and negligent act since the historic fundamental purpose of a fire hydrant is to provide water with which to fight fires. Finally, if your state has adopted the Uniform Fire Code, use of fire hydrants fall under the authority of the Fire Chief, not the water agency. Hope this information is helpful. Willis Lamm, Water Supply Officer |
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#36 - Can we use a sea water as a water source for pressurised hydrant system. If so, what type of pumps suitable for drawing water and is any corrosive protection required to pump impeller.Please advise me the design requirement and NFPA code number. Sea water is an acceptable and customary source of water that falls under the general classification of "Alternate Water Supply Systems." While there are not specific code specifications for seawater systems, most modern systems use all bronze pumps, PVC pipe of an appropriate schedule for the pressures involved and brass valves and fire hydrants to minimize corrosion. Willis Lamm, Water Supply Officer |
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