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Plumbing Math

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  • Plumbing Math

    Years ago while attending apprenticeship school, with Local 2, My Instructor gave me a formula for figuring out the amount of air left in an airchamber after the system was wet. It had something to do with volumes and pressures.

  • #2
    Re: Plumbing Math

    Boyles law ..need to know,volume of the airchamber,and absolute pressure....pressure and volume are inversely proportional,to find the volume of a charged airchamber,it would be say 14.7 psi,over say 12 cu. in.,at 65 psi of static pressure the volume would then be 2.213 cu in,but as any plumber knows,the volume of air in a non-sealed airchamber,after any given amount of time is zero.

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    • #3
      Re: Plumbing Math

      That is the one thing that the union would have exposed me to..More of the formulas for figuring different situations to ease installation and layout.Picked up a few over the years.

      Something I would like to learn is the rolling 45 degree offset.Straight 45 offset I was taught my first year.

      Where would a plumber apply the amount of volume in a chamber.Medical,industrial?I have tried to see where I would use this in my scope of work in commercial.Can't see anything yet.

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      • #4
        Re: Plumbing Math

        rolling offset is:
        This works when the angle between your roll and rise is 45 degree

        Roll(sq.) + Rise(sq.) + Run(sq.) = Travel(sq.)

        If your angle is not equal to 45 degree the formula is 2 steps

        rise(sq.) + run(sq.) = roll(sq.)

        Then, Roll(sq.) + Rise(sq.) + Run(sq.) = Travel(sq.)
        West Trail Mechanical Ltd
        Service. Commitment. Expertise.

        www.westtrailmechanical.ca

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        • #5
          Re: Plumbing Math

          For calculating a 45* offset----1.41 or for quick math 1.5

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          • #6
            Re: Plumbing Math

            You mean you guys don't stand under the pipe, waving your tape measure all around, squinting one eye and then have the apprentice cut a piece about say 15" long, Ok take an inch off, another 1/2, just a shave, Damn it's too short now.
            I tell my apprentices that if they can calculate offsets and rolling offsets they can do something better than half the masters in this state can't.
            sigpic

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            • #7
              Re: Plumbing Math

              Originally posted by NHMaster3015 View Post
              You mean you guys don't stand under the pipe, waving your tape measure all around, squinting one eye and then have the apprentice cut a piece about say 15" long, Ok take an inch off, another 1/2, just a shave, Damn it's too short now.
              I tell my apprentices that if they can calculate offsets and rolling offsets they can do something better than half the masters in this state can't.
              Thats funny. I do use the 1.41 for 45 only because a union friend taught it to me. Other than that I'm holding fittings and tape measures in the air. When I was working in Iraq they hired a lot of pipe fitters for plumbers. I would see them take all the center to center mesurements, adjust for take up of the fittings cut everything and glue it or screw it together. Most times it worked great. I was always amazed.
              Sometimes a guy could get a small job done faster by just measureing and cutting. It didn't matter to them----measure center to center then start figuring.

              So if you don't mind my asking whats a rolling offset?

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              • #8
                Re: Plumbing Math

                I second that, I would like to know, but have been thrown off so far by how it's been described so far in this thread.
                Proud To Be Union!!

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                • #9
                  Re: Plumbing Math

                  If you lay two 45's on the ground I call that a straight offset(I don't know the correct terminology).Easy,as you can just measure the center to center of the offset and multiply by Masterplumb's 1.41 then take off for your fittings.

                  Some times you need to roll your 45's off the same plane to get from point A to point B,a rolling offset.

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                  • #10
                    Re: Plumbing Math

                    Originally posted by bigPipe09 View Post
                    rolling offset is:
                    This works when the angle between your roll and rise is 45 degree

                    Roll(sq.) + Rise(sq.) + Run(sq.) = Travel(sq.)

                    If your angle is not equal to 45 degree the formula is 2 steps

                    rise(sq.) + run(sq.) = roll(sq.)

                    Then, Roll(sq.) + Rise(sq.) + Run(sq.) = Travel(sq.)
                    Thanks BigPipe I'm gonna give it a whirl.I hate the time wasted guessing and miss.

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                    • #11
                      Re: Plumbing Math

                      Remember that since the math is derived from the Phyagorean theorum (A squared plus B squared = C squared) all the measurments are taken from the center line. You need to have a manufacturers chart to get the make in allowance whic in turn needs to be subtracted from the actual pipe length. There are constants you can use for 22's, 60's 72's also. After you get all that down you can move on to paralell offsets and rolling offsets and paralell rolling offsets.
                      sigpic

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                      • #12
                        Re: Plumbing Math

                        I'm running out to the truck to lay some fittings out on the lawn to give this a shot.

                        Thanks guys!
                        Proud To Be Union!!

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                        • #13
                          Re: Plumbing Math

                          Makes sence Dirtyhands Thanks.

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                          • #14
                            Re: Plumbing Math

                            Originally posted by NHMaster3015 View Post
                            Remember that since the math is derived from the Phyagorean theorum (A squared plus B squared = C squared) all the measurments are taken from the center line. You need to have a manufacturers chart to get the make in allowance whic in turn needs to be subtracted from the actual pipe length. There are constants you can use for 22's, 60's 72's also. After you get all that down you can move on to paralell offsets and rolling offsets and paralell rolling offsets.

                            OK now I'm glad I've become a service plumber and bidet advocate and spokesperson. My gosh all the floor joists and studs and basement walls would be full of my tabulations If I knew how to do all that.

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                            • #15
                              Re: Plumbing Math

                              Alright guys, please hang in here with me, I learn faster in person/hands on, it's hard for me to understand this over the internet. I just laid out some fittings on the street.

                              A neighbor walked by and probably thought I was high on something laying pvc fittings out in the street at 8:30 at night, and measuring the air in between them.



                              When you guys talk about off sets, if this what your referring too?

                              Would the center to center measurement times 1.5 work with a lay out like this?

                              I tried and tried and couldn't get it to work out right.
                              Proud To Be Union!!

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