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Determining Flow Rate

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  • Determining Flow Rate

    I've thought about this question for a while now and maybe someone here has a answer . You have a commercial bldg. where determining flow rate and pressure are crucial to determine water distribution design , and I've bein taught the city service is usually at a flow rate of 5 gpm. , but some systems are at 10 gpm . I have bein taught to install a 3/4'' hose bib near the meter [ and a lot of systems have it already ] , to provide a testing station . Then I basically open the bib full bore and see how many gallons per minute flow there is. I question the 3/4 bib opening as opposed to a 1" shut-off because you have fixtures inside supplied by 1". Areas which have low gpm. flow at the service then needs assistance of booster pumps , gravity tanks ,etc. Does anyone have a credible surefire way to determine gpm. at the incoming service . I was always told as close to the meter as possible for testing .Thanks

  • #2
    Re: Determining Flow Rate

    Originally posted by apf View Post
    I've thought about this question for a while now and maybe someone here has a answer . You have a commercial bldg. where determining flow rate and pressure are crucial to determine water distribution design , and I've bein taught the city service is usually at a flow rate of 5 gpm. , but some systems are at 10 gpm . I have bein taught to install a 3/4'' hose bib near the meter [ and a lot of systems have it already ] , to provide a testing station . Then I basically open the bib full bore and see how many gallons per minute flow there is. I question the 3/4 bib opening as opposed to a 1" shut-off because you have fixtures inside supplied by 1". Areas which have low gpm. flow at the service then needs assistance of booster pumps , gravity tanks ,etc. Does anyone have a credible surefire way to determine gpm. at the incoming service . I was always told as close to the meter as possible for testing .Thanks
    I am not sure how much help I can be, I only have to size systems, if I call the water company they will give me a high and low pressure, then I can size my system, at most, calculate pressure loss per story. check this out
    http://www.toro.com/sprinklers/irrmi...uge.pdf#page=1. Sure they have a better one in a supply house, The water meter has a meter union on the customers side here in so cal, I would adapt it to that, then turn the meter on, hope this helps. good post, I need to learn this
    sigpic

    Robert

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    • #3
      Re: Determining Flow Rate

      i have a flow meter and a psi gauge that are 2 separate gauges incorporated into a 1'' manifold. this is a professional setup that is accurate to 3% of the gauge reading. it's great for sizing for systems and i just used it in a surgical center last week to get them the required flow for a sterilizer unit that required 10 gpm at 50 psi.

      unfortunately this set up is $750.00 to buy 1 of this accuracy and quality.

      you do need to read the flow through a full port valve and not a hose bibb.

      rick.
      phoebe it is

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      • #4
        Re: Determining Flow Rate

        Robert , excellent link...........I knew I was doing it old school .I figured there was a tool to test gpm flow. To tell the truth I am more isolated professionally here than I would like but it'll work out.In the town I'm leaving I have only two suppliers , and you're limited to using them or ordering through catalogs/on-line for a common part I could have gotten many places in any other city.They tell you to improvise [southern engineering ].The horror stories I could tell you..............

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        • #5
          Re: Determining Flow Rate

          if i'm not mistaking, that is the one home depot sells for approx. $50.00

          not too sure how accurate it is, but toro is a sprinkler co. i know that h.d. also rents them in the stores that have rental dept.

          rick.
          phoebe it is

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          • #6
            Re: Determining Flow Rate

            Rick , I always felt a full-port valve was the way to test as I hinted at in the initial thread .I learned my technique from a incredible master ,but as we all are aware , no-one knows everything . The mans name was Gerald Chadwell , originally out of Jersey area I believe .He had the distinction of being owner of the 6th. largest Mechanical company in the nation . I believe he and his sons re-plumbed West Point in the 80"s . THank-you both for your input .Rick ,I figured you would have a good working knowledge of this , Robert , you suprised me , Kudo"s...........dude.

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            • #7
              Re: Determining Flow Rate

              the only way you are going to get full volume is through a full port valve or open pipe. a hose bibb with a washer is too restrictive and will reduce your readings.

              very simple, install a full port valve with a hose adapter if needed.

              i have 3 different brands of hose bibbs. the full port ball valve, the garden style with a non rotating washer, and the typical no kink bibb.

              the ball valve style will flow the most. the garden bibb is not bad and will flow more than a hose connected to it. and the regular no kink with a 00 washer. this flows the least amount of water.

              do a 5 gallon bucket test and you can save all the headaches of doing your own research.

              rick.
              phoebe it is

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              • #8
                Re: Determining Flow Rate

                Rick ,that was always my stance on the subject as well , full-port all the way .My point was I didn't want to insult my Master plumber . I new his method was close , hadn"t come across this situation in a while [where I needed to know A PARTICULAR FLOW RATE ]. But It popped-in my head and I said "I'll go the Forum ", glad I did . I appreciate you guys

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                • #9
                  Re: Determining Flow Rate

                  Not sure where you are working at but I Know for a fact there are several maybe hundreds of types of meters and thousands of types of service line instalations. The size of the main line and size of the tap and size of the service line the length of the service line and type of water meter make huge differences in the flow rate. the type of meter setter and if there is a pressure regulator at the meter make huge differences. then after you get a handle on all that you can go to work on how far it is from the meter to your building or point of use. I dont' care who you are or what you think you know... in my expiriance with water service, there is nothing consistant. Just when you think you have seen it all... you will run into a litterbox..(where someone has burried a bunch of crap). there is no rule on how to put in a service, just that water supply has to maintain 25 psi at the meter. or atleast that is the rule here in rural OK.
                  Town codes may be more specific but times have changed in the last 50 years and what they put in for services then isn't what you are going to get with a new service now. I have all kinds of contraptions for checking pressure and flow at meters and service connections, drop me a line and maybe I might be able to help.
                  another point to be made is the pressure drop at what flow rate. What pressure you have to maintain to keep everything working properly in your building, we all know some fixtures dont' like big pressure swings. And no one likes water hammer. who would have thought you would use physics as a plumber huh>?
                  Last edited by S. tatum; 06-19-2007, 08:49 AM. Reason: another point

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