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100 feet of pipe is how much head?

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Rocky_3
Rocky_3 Member Posts: 232
It was a quickie estimation about how every 100 feet of pipe is approximately "x" amount of head, or something along those lines. This figure allowed for some fittings, the pipe, etc. Helped you to guestimate when trying to figure out what someone else did after the sheetrock is already on. Does anyone remember what I'm talking about?
Thanks,
Rocky

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  • Perry_3
    Perry_3 Member Posts: 498
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    Rocky

    Not sure if this will help; but:

    100 ft of verticle pipe = 100 ft of head - assuming static flow conditions(no flow).

    100 ft of absolutley horizontal pipe = 0 ft of head - assuming static flow conditions (no flow).

    Once you induce flow - things can change very widely depending on the amount of flow, the size of the pipe, the amount and type of fittings and other items in the system, and the internal condition of the pipe, fittings, and other items on the sytem. You might have very little head (a couple of feet) or thousands of feet of head.

    I would not be surprised if there are some genearl rule of thumbs out there based on size of headers and aproximate flow for normal residential heating. Yet, I wonder at the variables. I have a monoflow T system, do not use mixing valves, but does use a low loss header to take the boiler out of the picture.

    I hope someone else can provide a more common answer (if such exist).

    Perry
  • ALH_4
    ALH_4 Member Posts: 1,790
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    Head Loss

    Grundfos has a decent explanation right here.

    Head loss tables start on page 35, and there are equivalent lengths for fittings on page 56.

    Just estimate how many feet of pipe you have and add the equivalent length for each fitting and valve. A little trial and error and you can get pretty close to where on the pump curve the system will operate.
  • Rocky_3
    Rocky_3 Member Posts: 232
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    Forgot I had that exact Grundfos..

    book on my shelf. Pulled and found exactly what I was looking for. Thanks for reminding me what an excellent resource that particular Grundfos book is.

    Regards,
    Rocky
  • Dick Charland
    Dick Charland Member Posts: 178
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    Rule of thumb is to multiply total length x .06.
  • Brad White_9
    Brad White_9 Member Posts: 2,440
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    To Clarify

    The 0.06 factor would be applied against the length in feet. The presumption is that your flow rate is at a maximum and consistent "4.0 feet per 100 feet", to which is added 50% for fittings.

    Thus it works out to 6.0 feet per 100 feet or 0.06 feet per foot of pipe.

    Personally, I find that quite conservative and will yield higher heads than you would actually see, but you will not likely have an under-sized circulator! But it all depends on your design flow basis. I limit my "per 100 foot" head loss to about 2.4 feet, a little over 1 PSIG. (See Below)

    FYI, at about 4 feet per 100 feet, the following nominal Type M copper pipe sizes would give you these flow rates, followed by my own design chart flow rates in parentheses, for comparison:

    1/2" 1.5 GPM (1.0)

    3/4" 3.9 GPM (3.0)

    1" 8.0 GPM (5.0)

    1-1/4" 14.0 GPM (10.0)

    1-1/2" 21.5 GPM (18.0)

    2" 45 GPM (32.0)
  • Rocky_3
    Rocky_3 Member Posts: 232
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    Need to write all this down

    I should keep a pad and pen handy when I visit "The Wall" so I can write down all the little handy tidbits that I run across so I don't have to go searching for them when I need them again. Thanks again. That 6ft./100 ft of pipe was the figure I had heard previously.

    Regards,
    Rocky
  • Empire_2
    Empire_2 Member Posts: 2,343
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    Brad has it!!!

    Length out and back in feet, add 50% to this, Multiply by .04 = pump head. Quick way and not using technical CV values, but can get you in the ball park.

    Mike T.
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