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making sense

I look at the ratio of pipe diameters. (or area of their circles). Then useing the TEL select the one that you can use the easiest. Note: Copper has less head loss per foot than iron. I think W-M just wanted to get you started in the right direction. Of course to keep your flow in a reasonable laminar (not turbulent) flow is correct. Also, I've seen to high a flow cut copper ells apart. There is nothing like math to keep us realistic. After all TV is nothing more than math producing HDTV and good math produces good heat Also.
In this case 2" pipe is 75% larger than 1-1/2". the ratios
of your calculation run 72% + or -.
So go with the flow!


  • making sense of this

    please go to the w-m link below, and scroll to pg 15, and/or, just follow what i have below


    paragraph 5, Sizing system water piping

    2. ........To use this table, select a pipe size with a flow rate just larger than that required. ........

    3. ........(For type M copper piping, this means flow rates of: 1-inch — 5.5 to 10.9 gpm; 1¼” — 8.2 to 16.3 gpm;
    1½” — 11.4 to 22.9 gpm; 2” — 19.8 to 39.6 gpm.)......

    now look at fig13. a problem; do you see any of the above values in the chart?

    and now, look at their 'note' and 'examples'

    Total head loss for a piping circuit equals the loss per 100 feet times the TEL (total equivalent length) of the circuit in feet. TEL includes head loss for valves and fittings in equivalent feet of piping (i.e., how much straight length of piping would cause the same head loss as the valve or fitting). ok, no problem

    For example, if a piping circuit has a measure length of 250 feet, and includes valves and fittings with a total of 175 equivalent feet, the TEL for the circuit = 250 + 175 = 425 feet. again, no problem

    Consider the circuit given above, with a TEL of 425 feet. If the flow rate required for the circuit is 21 gpm, as in the example at left, select a pipe size from above.

    example from left: FLOW = 210,000/(20 x 500) = 21 gpm

    Using 1½-inch pipe would cause a head loss of 4.0 feet per 100 feet of piping. Since TEL is 425 feet, head loss would be: Head loss = 4.0 x 425 / 100 = 4.0 x 4.25 = 17.0 feet

    Using 2-inch piping would cause a head loss of 2.5 feet per 100 feet of piping. Since TEL is 425 feet, head loss would be: Head loss = 2.5 x 425 / 100 = 2.5 x 4.25 = 12.3 feet.

    so, from the 1st example, the math equates to 17, which is less than 19 AND 23

    and in the 2nd example, while their math is incorrect @ 12.3(it should be 10.63) but either value is less than 19 AND 23, but not, "a flow rate just larger than that required." the values, 19 and 23 are, by comparison, much larger than 12.3(10.63)

    so, is that the point? a value that closer/lower than the 19 and 23? and if so, if we needed 38gpm, then the 2" pipe would be our choice?

    weil my guitar gently weeps, i'll patiently await an answer
  • thanks for the response gary

    but if you will, go to the 'hey ME' thread, bec the details with spicoli may explain my confusion a bit more
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