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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 mailbag. If you have a question, Email Us.
  • The viewpoints expressed in this forum on these pages are those of the participants.
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  • #61 - We are building a stone wall structure near a fire hydrant in our yard. Do you know of any uniform laws or rules of thumb in the USA that prevent structures within a certain number of feet from a fire hydrant?

    The Uniform Fire Code specifies, among other things, that a clear space of not less than three (3) feet be maintained around all fire hydrants. It also states that access and identification (clear view) of hydrants be unobstructed.

    Therefore a wall needs to be staggered back at the hydrant if necessary to maintain a three foot clearance and it can't be designed in a way that unreasonably obstructs the view of fire personnel looking for it nor create any impediment between the hydrant and the street that could block rapid connection of hose lines.

    Since stones come in a variety of shapes, most often people form the walls in a semi-circle around hydrants when a set back is necessary as that flowing design looks more attractive.

    Hope this info helps.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda FD

    #62 - Is there a standard protocol for opening and closing hydrants and is there literature on this subject? Also how may turns does it take to close a hydrant valve? Could improper operation of a fire hydrant cause water hammer that would have adverse effects on potable water in the local area, particularly a possible pressure spike? thanks much.

    It pretty much depends on the make and model of hydrant, volume flowed, main capacity and length of main. Rapidly shutting down a free flowing fire hydrant in some systems can cause enough water hammer to burst water mains and/or fire sprinkler systems.

    A good field experiment is this:

  • Pick a hydrant to open and close.
  • Put a pressure gauge on the next hydrant down the line, open it and take a reading.
  • Open the test hydrant fully, then close it as is normally done in your area.
  • Read the pressure spike when the hydrant is closed.
  • If the pressure rises over 20 psi or over 20% of the original static pressure then it is likely that the hydrant is being closed down too quickly. Repeat the experiment closing more slowly. When you can close the hydrant within the "spike allowance" then you are closing it slowly enough.

    Hope this information helps.

    ":O) Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

    #63 - Is there a minimum and maximum distance from a fire Hydrant the Isolation Valve is required to be? What is standard or acceptable distance? Thanks

    In most jurisdictions the valve can be installed virtually anywhere between the tee and the hydrant bury. It should be in a location that is reasonably accessible. (Under a parking space or so close to the hydrant that it would be useless if the hydrant is sheared off and water is pummeling down would be examples of not reasonably accessible locations.) In the East Bay, Roman numerals are painted on hydrants or curb faces that indicate the distance in feet from the indicator to the valve pot.

    In San Francisco, for example, the street valves are usually a couple of feet from the water main tee to keep them out in the traveled portion of the street. (The lids of hydrant valve pots are typically painted white for ease of identification.)

    Hope this information helps.

    ":O) Willis Lamm, Water Supply Officer
    Moraga-Orinda F.D.

    #64 - Would relocating a firehydrant be a problem or would it depend on the particulars of the situation? If I am facing a problem with parking in my neighborhood and the hydrant is on the front of my home what steps can I take to have the hydrant moved down the block?

    First off someone is probably going have to come up with the $10k or so it will cost to kill the old hydrant, remove or cap off the lateral in the street and make the new installation.

    Once the financial matter is addressed, the next step involves the actual hydrant relocation. The issues at play include spacing between hydrants, distance to protected structures and aggregate required fire flow (flow required from multiple hydrants.) In suburban areas with average size single family homes separated from each other this is not such a significant issue unless hydrant spacing is already stretched to the max. In more urban locations with multi floor multi family structures, particularly when they are situated next to each other, or with row houses that are tucked right next to each other, hydrant location is critical. The required number of hydrants for aggregate flow have to be within specific distances to all of the structures.

    The most likely relocation option would be to place the hydrant right next to a nearby driveway that someone wouldn't want blocked anyway and position the body so that the pumper outlet faces the corner of the street and driveway. If the FD went along with it, the size of the "red zone" needed next to the hydrant could be reduced and you might pick up an additional parking space that way. I guess the big question in this whole concept, however, is how much an additional parking space is worth in your neighborhood!

    ":O) Willis

    #65 - I have to put in a water system in Sierra County that calls for a hydrant with a 4 1/2" hose outlet. It's a draft system with only a 2500 gallon tank I need to know if anyone makes a wharf hydrant with a 4 1/2" outlet. Thank you.

    James Jones Co. has produced a wharf with a 4" outlet however it only has a 4" inlet. They also produce a 4" x 2" "L.A." hydrant that threads onto a 6" pipe if that would better suit your needs. Actually the most cost-effective solution is to buy a salvaged steamer hydrant and bolt it down to a 6" companion flange.

    I'm curious here. If it's a gravity system, how are you going to keep the hydrant from freezing? If it's a draft system (hydrant set above the tank) then all you really need is a long radius elbow and a pipe thread to 4"NH adapter.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

    #66 - My fire system loop valves are about 3' underground. To comply with section 4-3 NFPA 850, Valve Supervision, does anyone make a locking device for roadway boxes?

    It's our agency's interpretation, and that of every other agency that I know of, that NFPA 850's valve supervision standards apply to above ground valves such as PIVs or OS&Y valves. These above ground valves are something that an arsonist or prankster would see and possibly tamper with. Supervision means that some form of alarm should register if someone closes or tampers with those valves. These devices are also required to be kept locked. I'm not aware of anyone locking or supervising ordinary underground gate valves that are used only to isolate segments of a system or to control branch lines for yard hydrants.

    If you have additional security issues above and beyond normal fire suppression, I might suggest you place three or four good size drops of traffic reflector epoxy under the lip of the gate pot lids so that it takes some work with a concrete bar to open them. That's how we deal with lids that tend to flip open due to unusual topography and traffic speeds.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

    #67 - I am the Deputy Fire Chief for [a fire department] in Northeast Mississippi. Our town has been serviced by a rural water department, for the past twenty years. The system has to upgraded due to an increase in the population. The local water department. has asked the city board for help in obtaining a grant for expansion of the system. The fire dept. saw the opportunity to have hydrants placed on the lines that are capable of supporting hydrants (4" or larger is my understanding) The water department does not want the hydrants to be placed on the system, they think that we will collapse the lines if we hook onto a hydrant. The system has a static pressure of 58 PSI on the hydrant we currently have.

    The mayor and board supports the fire department in our quest for an improved ISO Rating, but we need ammunition to use against the water department.

    Now that you know some background info, these are my questions:

  • #1 Are there any US codes in regards to hydrant placement?
  • #2 Are there any Mississippi codes in regards to hydrants?
  • #3 Is there anyone that could help me explain that a pumper using a 3" soft suction hose should not collapse a line that has 50 PSI static pressure?
  • Please Email me with any help or advise. Allow me to thank you in advance,

    You are correct. It is a ridiculous presumption on the part of the water department that flowing water from fire hydrants will collapse water mains. I question the engineering credentials of anyone that would advance such a theory.

    For example the City of Alameda, CA has a number of cast iron mains ranging in size from 4" to 16" that date back as early as 1880. They also have hydrants on every corner. There are no current plans to replace these mains as they are providing adequate service.

    In the suburban jurisdiction where I work many mains date back to the early 1930s. We are replacing many of ours but it's because we're in an extreme fire danger area and we need better fire flows.

    In some specific circumstances there can be an issue relating to water hammer. These instances typically involve hillside communities where the static pressure at the bottom of the system oftentimes exceeds 150 psi and there are long dead-end runs of water main. In such instances shutting down a hydrant too quickly could cause leaks in 1940s vintage "CM" type mains (thin cast iron that is mortar lined). Those, however, are specific instances. I've never seen a hydrant caused leak in a properly installed PVC, steel or unlined cast iron main.

    > The mayor and board supports the fire department in our quest for an
    >improved ISO Rating, but we need ammunition to use against the water
    > department.

    Unless your water department is hiding some really shabby construction, this should be a no brainer. I'd definitely tie the town's grant support to also providing fire hydrants. (That's what the rural town where I live did and the public safety aspect helped get our grant placed high enough on the list to be funded.)

    I would suggest, since you're probably in an area where you don't experience long, hard freezes, that you look into using wet barrel hydrants. They are easier to control on shut down (reduces water hammer), are easier to maintain and repair, and both outlets are independently operated (horizontal above ground valves) so you can add hose to and open a second or third outlet without having to shut down the hydrant. I've attached a photo of a James Jones model 4040 that was in our hydrant shop.

    > Now that you know some background info, these are my questions:
    > #1 Are there any US codes in regards to hydrant placement?

    Yes. NFPA sets standards for placement. Here is a feature that discusses this issue.

    The AWWA (that your water department should subscribe to) publishes hydrant specifications in its M-17 pamphlet. (I'm a member of the M-17 Committee.)

    > #2 Are there any Mississippi codes in regards to hydrants?

    Your State Fire Marshal can answer better than I. Most states have adopted the Uniform Fire Code. As a practical matter the UFC codes generally state that the subject of fire hydrants falls under the authority of the fire chief (or his/her designate.)

    > #3 Is there anyone that could help me explain that a pumper using
    > a 3" soft suction hose should not collapse a line that has 50 PSI static pressure?

    This is so basic I'm not sure that it's covered in any texts. It's like breathing air or that gravity pulls things to earth. It something that just is. Maybe your water department guru should be required to explain in scientific terms how a fire engine could pull such a vacuum on a soft line (which will go flat if the suction exceeds supply) to the extent that it would create negative pressure in a public water system. I realize that this sounds condescending but I've really got to hear this one. Ask him to hook a fire hose to his household water faucet and see if it collapses the pipes in his house. The fact it is that hydrants will only deliver what the mains will supply and unless someone tried to draft with hard suction, whether an engine is connected or not is little different that removing a cap and discharging water into the street.

    There are a couple of water quality issues you should consider. If your community is reasonably flat it may not apply to you. In communities that have elevation changes in their water systems (due to hills) it's standard practice not to pull any hydrant down below 10 psi residual on the engine's compound gauge when pumping. This procedure protects the upper parts of the system from losing pressure when lower parts of the system are being pumped. A standard operating procedure for pump operators not to pump below 10 psi residual will address this issue and will also help ensure that you don't collapse your suction line, whether you use 3" or large diameter.

    The second water quality issue involves annual flushing of fire hydrants. When properly done, flushing helps remove debris and contaminants from the water system. For example, the rural town where I live had e.coli issues with its water system until we finally got fire hydrants installed. Now the fire department coordinates its annual fire hydrant testing with the water department so that the mains are flushed when most appropriate for public health reasons. It was messy the first year because there was so much junk in the mains (they had to tell everyone not to do their laundry on the first main flushing day) but once years of accumulated contaminants were removed, the system stayed pretty clean. Plus if water tests concerned the water company inspector, it was easier for a water crew to open a fire hydrant to flush out the system than either opening a "blowoff valve" in the middle of the street or having to ask several residents to run their yard spigots all at one time.

    If I can be of any further help, please feel free to contact me.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) Fire District
    Member - American Water Works Assn M-17 Hydrant Standards Committee

    #68 - We operate exclusively off a hydrant system, never needing to draft, and are currently debating whether we should switch from 3" supply line to 5" supply line. Is there that much of a difference between running dual 3" lines as opposed to one 5" line. Also, our water mains range in size from 4" to 12 ". Wouldn't we be taxing the system if we connected a 5" supply line to a hydrant with a 4" main?

    5" Supply line is about 25% more efficient than dual 3" lines. Improved efficiency results in lower friction loss when drawing large volumes of water. If long hose lays are an issue then you'll likely experience an improvement if you switch to LDH. If you typically lay from hydrant to fire and your dual 3" lines never leave you short on residual pressure, then you may not see much of an improvement.

    It doesn't matter if you use LDH on a 12" main or a 4" main. The main is still only going to deliver what it can. The difference is you'll have less friction loss to deal with using the 5" hose.

    Another determining issue may be your ISO rating. Some communities get killed by the Table of Distances when ISO grades their water systems. The hydrants may be adequate for the buildings being surveyed, but they are so far away that they only receive a fraction of their total capacity toward fire flow credits. If every engine that is normally assigned to structure fires in the community carries LDH, the Table of Distances no longer applies. Every structure gets full credit for every hydrant within the distance of the smallest LDH hose load.

    That means if each engine carries at least 1000 Ft. of LDH, every hydrant within 1000 ft every building ISO surveys will be given full credit, up to the available aggregate flow of the mains (all required hydrants flowing simultaneously.) Since water supply makes up 40% of a fire department's total rating, being able to use all the available water in the water system when calculating available water supply versus required water supply can often mean the difference between a better versus a poorer protection class rating. I'd check with your region's ISO inspector and see if for your community going to LDH would result in a significant improvement in your next ISO rating.

    Hope this information is useful.

    ":O) Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

    #69 - We have a fire hydrant that sits at the end of our driveway leaving at one point as little as an 18" clearance when backing out. We have accidentally hit this hydrant and it is a constant nuisance to anyone trying to back out. Are there any uniform code requirements stating just how far away from a driveway the hydrant needs to be?

    An 18" setback is appropriate. It sounds to me like that from a practical standpoint the hydrant is set awfully close to the turning radius of vehicles entering and exiting the driveway (too close to the corner of the junction of the driveway and curb line.) That doesn't mean that it's not a legal installation, but rather an undesirable one.

    In these kinds of situations we try to set hydrants behind the sidewalk so that they won't be clipped by vehicles turning in or backing out. Of course not every physical layout is conducive to this placement but when possible it still provides useful immediate access by the fire department since it's not likely that someone will park in front of it and obstruct it.

    The problem you have is that even if your situation would be conducive to moving the hydrant back behind the sidewalk, it's a very expensive proposition to remove a hydrant, extend the pipe, pour new concrete thrust blocks and replace the sidewalk and the issue becomes who is going to pay for it.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

    #70 - I am designing a new fire line on an existing school site to protect proposed new relocatable buildings. Since I don't have a lot of experience with this calculation, I would like to confirm my understanding of how to use the flow test data. The data given is static pressure, residual pressure at an observed flow rate and a calculated residual pressure at 20 psi.

    The 20 psi residual figure can be pretty confusing. It's basically a reference value; the lowest pressure that the fire department would want to draw down a hydrant. Therefore it is used in the Hazen-Williams formula to make the math work in order to determine what a hydrant COULD flow based on the volume and residual pressure read with only one outlet flowing.

    If I'm calculating a main extension I would first flow test the hydrant on the main closest to the proposed extension and at the same time take secondary readings during the test from a static connection nearby (e.g, another hydrant, hose bibb, etc.) Based on the observed flow at the hydrant I could estimate the main capacity. I might conduct a second test whereupon the additional nozzles are flowed from the hydrant to equal or slightly exceed the required fire flow needed from the main extension. That would allow me to get a fair handle on what residual pressures remain in the main during the required flow. That would be my basis for calculating the necessary diameter for the extension.

    Let's say for example that I need to deliver 2,000 GPM and the main holds at 45 psi at my test location with 2,000 GPM flowing. If the hydrant has a 4" pumper outlet I'll probably need a minimum of 23 psi at the hydrant to sustain the flow (depending on the hydrant design.) If by using standard FL tables I design for less than 22 psi total head loss through the entire extension layout AND the hydrant bury, I'll have sufficient head to meet the flow requirement.

    If the required fire flow is 1500 GPM, I could probably calc for a 17 psi residual at the hydrant fully flowing since through a 4" nozzle it takes less than 15 psi to discharge the required flow and a hookup into a hose flowing only the required fire flow would typically generate enough back pressure to maintain 20 psi residual.

    The numbers I'm using are relative since different hydrant designs, nozzle sizes and coefficients all play a part in the calculations.

    Since these types of systems have a tendency to be expanded upon in future years, I'd recommend increasing the extension diameter by one pipe size if your calculations run close. I've seen a number of these systems turn out to be a couple hundred GPM short when domestic demand pulls down the grid or the reservoir level drops a couple dozen feet, or they won't meet required flows at the end of additional extensions that may later be required.

    I hope this approach makes sense to you. If you have additional questions please write.

    Willis Lamm, Water Supply Officer
    Moraga-Orinda (CA) F.D.

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