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  • #16
    OK, I was going to stay out of this mess, but since my name was brought up...

    LT334

    If you put a pitot flow gauge on a 2 1/2 outlet and flow it, can you use the chart to convert this reading to gpm rating for that hydrant,

    Yes, you can convert to the gpm rating for the pitot'd pressure for that hydrant.

    Problems with just doing it that way that have been pointed out but may not be clear for various reasons:

    All you get is the flow pressure for that hydrant at that time of day under the current use of the water system at that specific point and time in history.

    The information you get from tapping an upstream hydrant for the static and residual is what's left in the system, and graphs or computer programs like FireHouse, Fire Programs, Crossfire and others can extrapolate that information out to what the hydrant will do when the pressure is less, specifically down to 20psi residual (which if I understand correctly is minimum for municiple water systems - anyone feel free to correct me if I am in error here). Some programs can take it to zero for you as well.

    Why wouldnt the flow at that specific pressure be good enough. Would it fluxuate enough to actually make much of a change?

    Depending on what's going on with your water system, it can. More trucks on the system, main closures, unforseen restrictions, etc...

    wHAT IF THE HYDRANT YOU ARE TESTING IS AT THE END OF THE WATER MAIN AND YOU HAVE NO DOWNSTEAM HYDRANT TO FLOW?

    Just flow that hydrant, get the static and residual off the next upstream one.

    play.

    1. Dead end main. Flow test the end most hydrant and use a gauge off a house spigot to get the static is the by the book, exact way to conduct the test.

    Are you saying that a static/residual off the upstream hydrant is incorrect on dead ends?

    blackb16

    LET'S TRY A MONGO for am/fm

    What? You don't like my style?

    You forgot to use italics...

    LT334

    At least you guys can all be proud of the fact that someone is at least attempting to test your hydrants. no-one in my town is.

    Aren't you?

    [ 08-27-2001: Message edited by: mongofire_99 ]
    It's only my opinion. I do not speak for any group or organization I belong to or associate with or people I know - especially my employer. If you like it, we can share it, you don't have to give me credit. If you don't, we are allowed to disagree too (but be ready to be challenged, you may be on to something I'm not). That's what makes America great!

    Comment


    • #17
      Thanks mongo (and everyone else). That clears things up a bit. To answer your question, NO, no-one in my town is. (But im working on it)

      Comment


      • #18
        Well, this has been quite an exchange of info.

        Lets delve into the 20 psi question. My understanding is that this allows enough water/pressure in the system for domestic /industrial needs. A good pump operator can drop to 10 psi or less and not cause any major problems.

        The old timers used to claim that if you pulled a vacuum in the water main, you would pull a hydrant out of the ground. I have never seen this happen and do not think it is possible unless there is prior damage to the hydrant.

        What I have witnessed over more years than I care to reveal is damage to old water mains due to collapse or breaks at joints or elbows.

        The second problem I have witnessed is the suction of water from homes/commercial buildings. Newer structures are supposed to have a backflow preventer (check valve) in the service line to prevent this from happening. Old services do not have them. This can lead to the collapse of hot water heaters when a suction is applied to them. They look like a crushed soda can.

        You can bet that the media will cover the damages caused more extensively than your firefighting operation no matter how well you did. The Fire Chief will probably need the one hundred tablet bottle of asprin if this happens.

        Stay Safe and check your water supplies.

        Comment


        • #19
          I don't want to "muddy the waters" (pun intended)with a bunch of technicalities, but I think it needs to be clearly pointed out that the purpose of doing a flow test of a hydrant is to obtain the hydraulic characteristic flow curve for that particular water main feeding that hydrant. Any pressure readings (static OR residual) are only considered to be accurate for that one point in time that the flow test is conducted. However, assuming no valves are opened or closed in the system, the flow curve for that water main should remain the same no matter what the pressures are. Most public utilities or water purveyors can provide you with their expected low pressures for a given area, based on their minimum water level supplying that area - with that information, you can adjust your flow curve to the low pressure and have a somewhat accurate idea of the minimum expected flows available from that hydrant.

          Clear as mud?
          An ounce of prevention is worth a pound of cure!

          Comment


          • #20
            Was out of town and wasn't able to check the site.

            I still believe that play and blackb16 may be the same person, however I'll play (no pun intended) along and respond.

            While NFPA and AWWA all suggest that more than one hydrant be used for flow testing, my experience, (practical) is that;
            1. Flow test data received by my office, for use in determining necessary flow and pressure data for sprinkler systems provides just one flow hydrant. This includes two of the largest water utilities in my state. Both are members of AWWA and NFPA. If the boys in the business don't follow the standard...?
            2. My experience with flow tests have been that I don't have the manpower or time to test more than one flow hydrant, and the information that I have received from flowing more than one has not produced a significant difference than flowing one hydrant. This difference has proven to be less than 5%. Therefore my experience (practical application) has proven more efficient and effective.

            As far as getting good information I can't qualify that because he wasn't specific enough about his operation and the water system to provide that answer. Just as you have alluded to in your responses. As far as if his application being more practical, again I can't answer that but not in my jurisdiction where forward and reverse lays are used frequently.

            As far as looping dead end mains, there are good reasons to loop dead end mains. In locations where small mains were installed years ago, because there was little or no contact or control over water supplies provided by the water companies in the past with the AHJ looping may provide much better supply than a dead end main of the same size. Our water utilities sole purpose was to provide a potable water source. Fire flow was never considered. Four and six inch mains are common in our area, even in high flow, industrial areas. We have been successful with one water utility in getting developers to make improvements to the water systems where they are creating the hazards and risks. This utility will not sign water agreements with a developer until they receive a letter from our office listing the water supply necessary for fire control. We use the ISO formulas to determine that flow rate. Do I live in a utopia? No, but our efforts to have these improvements made, have made the job of the fire companies much easier when the fire occurs, and not at the expense of the taxpayer.

            Additionally, while there is much development taking place in our little neck of the woods here, the development is from residential to commercial and business as well as industrial. I think that you would agree that these hazards generally require higher flows that residential developments. Looping mains not only provide more water based upon the same size main (a looped 6 inch will provide more water than a dead end 6 inch) with proper valving it provides a more reliable water source with fewer areas subject to outages if a failure occurs. See page 193, Pump Operators Handbook, by Warren Isman, Fire Engineering, 1984.

            The 20 psi figure provides as I said an extrapolation of what is available, at that time and date that the water system was tested. 20 psi is the pressure that has customarly been used both by ISFTA, NFPA and others to report since that is the recommended minimum pressure for fire apparatus use. See page 11-54, NFPA Fire Protection Handbook, 14th edition.

            The 20 psi pressure is also what is used as a residual pressure in relay operations. KISS is a valuable and proven theory. It has seemed to work for me in the past. I don't believe that I'll change that yet.

            The danger of taking the pressure below 20 psi is not in "pulling the hydrant out of the ground, or collapsing the main", but when a pump tries to pump more water that it is being provided by a supplied source than cavitation occurs. When this occurs damage is immediate and irreperable. The 20 psi residual provides for a safety factor if conditions change during a fire operation. This gives the pump operator time to react to the problem and adjust where necessary.

            If a department uses any four-way valve at the hydrant in a forward lay, and if testing has been done and it has been determined that water may be available in the hydrant to flow the full fire flow amount from that one hydrant, wouldn't you want to get it all from that one hydrant? I think so. If the first in engine forward lays using that four way valve, and the second positions to reverse lay if necessary to the same hydrant that the first layed from, then we only pick up the hose that was layed from the closest hydrant. Not hundreds of feet further than the first hydrant, thereby requiring less effort to pick up more hose than was necessary. I think thats a practical application, isn't it? Why then does size of hose matter in this evolution. I can lay dual five inch hose both forward and reverse if I need to from the first and second engine, and supply it from the same hydrant if necessary.

            As far as flow testing a dead end main why don't you direct me to a publication that provides the correct way. The way that I described it in my past posts have always proven to within a hundred gallons per minute in the past, for me. I am always willing to learn from others regardless of the demeaning way in which it is presented.

            Thanks Larry for the conversation.

            Comment


            • #21
              While NFPA and AWWA all suggest that more than one hydrant be used for flow testing, my experience, (practical) is that;
              1. Flow test data received by my office, for use in determining necessary flow and pressure data for sprinkler systems provides just one flow hydrant. This includes two of the largest water utilities in my state. Both are members of AWWA and NFPA. If the boys in the business don't follow the standard...?


              I guess that is why so many sprinkled buildings don't get their insurance break after a few years. Ask ISO they can list thousands of buildings built to a made up inaccurate number. Lets all do every thing half asked. I guess following the standards we like the way we like them is why so many guys die in buildings with their PASS devices off, or with pre-existing medical problems, or driving like idiots, or are in lousy health and suddenly die weekly.

              2. My experience with flow tests have been that I don't have the manpower or time to test more than one flow hydrant, and the information that I have received from flowing more than one has not produced a significant difference than flowing one hydrant. This difference has proven to be less than 5%. Therefore my experience (practical application) has proven more efficient and effective.

              Oh here we go again, ball park 5%, 15% etc. Last time 650% counted as 15%. You don't have three guys do do a hydrant test correctly??? Odds are it takes two to do it wrong.

              As far as looping dead end mains, there are good reasons to loop dead end mains.

              AWWA and NFPA say there is no reason to if you follow their standards. If not heck any thing goes I guess.

              Our water utilities sole purpose was to provide a potable water source. Fire flow was never considered. Four and six inch mains are common in our area, even in high flow, industrial areas.

              Maybe that is why you don't see any difference in a flow test. Don't use your no code system to give advice to others especially when it flys in the face of all the standards. You can't possibll draw down a 10, 12 or larger main with one hydrant. Source NFPA handbook. Why do allthe standards suggest using three and four hydrants on certain configurations of mains? Because that is what it takes to do the test corerectly.

              until they receive a letter from our office listing the water supply necessary for fire control. We use the ISO formulas to determine that flow rate.

              So how do you determine the main size, needed flow, hydrant spacing, number of hydrants and growth in the system may I ask? What do you use for a standard? You base the supply on a half asked single hydrant test???

              Looping mains not only provide more water based upon the same size main (a looped 6 inch will provide more water than a dead end 6 inch)

              Then again NFPA, all the model codes and AWWA the topic of the discussion don't suggest that sized pipe in that application now do they? SO sue yo want to run silly sizes with more silly sizes knock yourself out, but the laws of the land and the standards all beg to differ with you.


              20 psi is the pressure that has customarly been used both by ISFTA, NFPA and others to report since that is the recommended minimum pressure for fire apparatus use.

              Oh it is a "custom"??? For a reverse lay see UFC Apx III, ISO will credit 0 psi.

              [i]The 20 psi pressure is also what is used as a residual pressure in relay operations.

              5 psi is used by ISO for relays residential and commercial. 20 psi is a real waste with big or small hose. SO how much water is a 20 psi residual?


              The danger of taking the pressure below 20 psi is not in "pulling the hydrant out of the ground, or collapsing the main", but when a pump tries to pump more water that it is being provided by a supplied source than cavitation occurs. When this occurs damage is immediate and irreperable. The 20 psi residual provides for a safety factor if conditions change during a fire operation. This gives the pump operator time to react to the problem and adjust where necessary.

              What damage are you talking about? The 20 psi residual has nothing to do with your cavitating your pump or not, that would be the operators fault. So how much of a safety factor in real terms is 20 psi? How much time does it give the pump operator? You can have cavitation with a 500 psi hydrant. If you over pump the supply cavitation occurs.

              If a department uses any four-way valve at the hydrant in a forward lay, and if testing has been done and it has been determined that water may be available in the hydrant to flow the full fire flow amount from that one hydrant, wouldn't you want to get it all from that one hydrant?

              Most four way valves cannot pump the rating of the pumper and cost you at least 25 to 33% in a forward lay. Why not just lay a second line or a larger single line and get twice the flow without the relay at what 1/60th the cost???


              If the first in engine forward lays

              Are you sure you don't need 1/4 to 1/3 of the hydrant flow on the initial attack?

              I think thats a practical application, isn't it?

              Why not do the math, which was the purpose of this post in the first place, buy the right size hose and have each pumper supply itself? Are two pumpers at half their capacity efficient? I think not.

              Why then does size of hose matter in this evolution. I can lay dual five inch hose both forward and reverse if I need to from the first and second engine, and supply it from the same hydrant if necessary.

              So why all the chat about four ways, reverse lays, etc?

              [i]As far as flow testing a dead end main why don't you direct me to a publication that provides the correct way.

              ISO FIELD PROCEDURES MANUAL. Their source of course is AWWA.

              The way that I described it in my past posts have always proven to within a hundred gallons per minute in the past,

              Always, Yeah right. So how did you get your residual and always be right f you didn't test the TEST hydrant. Sounds like BS to me. Find a source thart will support you on this, good luck.

              Garbage in and garbage out. If you don't base what you do on a standard odds are you'll never be right. The standards and law folks didn't waste all this paper so you could do your own thing and give bad advice to building owners, but then again you've said over and over your not doing things right. So I guess we should take your advice with a grain of salt.

              [ 09-06-2001: Message edited by: blackb16 ]

              Comment


              • #22
                play, blackb16 or is it Larry?

                I would agree with you that there are many things on the fireground that we shouldn't compromise on; safety being one. But my job requires me to do the best that I can with the limited resources that have been provided by my supervisor and within the restrictions set by the taxpayers. NO LARRY I DON'T HAVE THREE PEOPLE TO DO FLOW TESTS. As strange as that may sound to you, there are actually communities that think that recreation is more important that fire protection. Then again you problably couldn't find a picture of me in a trade journal with my protective coat open and my helmet strap over the back of my leather either.

                "AWWA and NFPA say there is no reason to if you follow their standards. If not heck any thing goes I guess."

                Does this mean that you agree with everything that NFPA prints? Does this mean that you dissagree with Ismans book and that looped fire mains are more reliable and provide fewer outages when properly equipped with isolation valves? The fact of the matter is Larry, not every city particularly on the east has newer infrastructure. We have to deal with problems you only could dream about in your worst nightmares. Not every town is as new and as shiny as yours in Nevada.

                "So how do you determine the main size, needed flow, hydrant spacing, number of hydrants and growth in the system may I ask? What do you use for a standard?"

                I told you what I use to determine the necessary fire flow Larry. We use the ISO Grading Schedule. I thought that an all knowing and all powerful fire god like you would be familiar with that. I didn't and will not tell the water utility what the hydrant spacing, main size, number of hydrants or growth will be because of things such as Water Tarif Agreements that have been determined by the State Water Utility Commission and Local Land Development and Zoning Requirements dictate these things. I only provide the required fire flow. The developer and the water utility determine though their water agreement how to get that flow.

                "Then again NFPA, all the model codes and AWWA the topic of the discussion don't suggest that sized pipe in that application now do they? SO sue yo want to run silly sizes with more silly sizes knock yourself out, but the laws of the land and the standards all beg to differ with you."

                What I want is a new water system that I have more control over but that isn't likely to happen in my lifetime. The size pipe that I get is what the water company says will supply the amount that we provide in the letter to the water company. That figure is arrived at using a well known and established procedure. Sometimes this means putting in new larger sized mains, sometimes it means using whats already there. But what size pipe to use is NOT UP TO ME. I don't have the legal right to do that here.

                "What damage are you talking about? The 20 psi residual has nothing to do with your cavitating your pump or not, that would be the operators fault."

                Are you saying that pump cavitation can only be the result of operator error? There are times that these failures have been the result of improper attention by the operator, however I can think of several things that may cause this to occur, none of which the operator has much control over. The 20 psi provides for a margin of error to allow the pump operator to determine what is happening and shut down the pump.

                Four way valves gives you the ability to establish a water supply and also get additional water from that same hydrant without shuting the source off. Do you disagree? If you don't disagree then why go the the next hydrant that may be hundreds of feet further than the one already being used. Additional engines can be used to not only lay additional supply lines they can be used to increase the water supply in the first line. This may also maximize the use of the hydrant. LARRY, HOW IS THIS WRONG?

                "Are two pumpers at half their capacity efficient? I think not."

                But how about two pumpers operating at full capacity, and laying less hose? Guess you forgot about the poor guys that had to pick it up didn't ya, Larry. Is an engine only half as good when its on the hydrant?

                "The standards and law folks didn't waste all this paper so you could do your own thing and give bad advice to building owners,"

                I don't give advise to building owners. I enforce our code. This code is not the best and it's not the worst and it surely has many problems. But it is like any code. It is nothing more than a political document. They are written by politicians and voted upon by politicians. They can be changed by politicians. Everything is not just black and white Larry, and if you got everthing that you wanted, you'd still be employed by that magazine, with that wonderful picture of yourself with the open coat and helmet strap around the back.

                I'd love to spend more time with ya, but like my Daddy says, "Ya shouldn't argue with an idiot son. Others may not necessarily know who the idiot is."

                Just my two cents worth and that won't buy even one.

                Comment

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