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WATER SUPPLY PIPING FOR BUILDINGS PLUMBING OBJECTIVE: The correct method of properly sizing plumbing pipes. Piped in water supply systems have become an essential ... – PowerPoint PPT presentation

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  • PLUMBING OBJECTIVE The correct method of
    properly sizing plumbing pipes.
  • Piped in water supply systems have become an
    essential part of society. Think as you got up
    this morning what it would have been like if you
    didnt have water. Perhaps you couldnt get a
    drink, brush your teeth, or flush a toilet.
    Indeed life would be a little different.
  • Thank goodness for the folks who pioneered
    plumbing. It probably is the most convenient,
    yet most taken for granted part of our modern
    technology. Truly this is a system we dont
    notice when it is there and works. But abruptly
    do without plumbing, and life gets miserable.
  • There are two primary parts of plumbing.
  • Water supply piping
  • Piping for waste getting rid of all that
  • Supply piping has evolved with modern
    technology. In the earliest times, pipe was made
    of wrought iron, and was not easily worked.
    Piping then changed to steel, then galvanized
    steel with a coating of zinc to retard rust.
    Installation was difficult because pipe joints
    had to be threaded and joined with fittings to
    make the system water-tight.

  • Installation of steel piping was slow and
    tedious, because lengths between fittings had to
    be cut exact, then fastened together with
    threaded joints, one following another in
  • Copper pipe was developed, along with a new
    type of fitting to connect joints. Pipe and
    joints no longer needed to be threaded. Copper
    piping is joined together with brass fittings, in
    a connection called a sweated Joint. A brass
    fitting is heated with a gas torch so the
    material expands. While it is still hot, the
    fitting easily slides over the outside of the end
    of the pipe, and when it cools, the fitting
    contracts against the pipe to make a tight fit.
    The connection is then soldered.
  • Plastic piping, such as polyvinylchloride (PVC)
    was developed into an economical and efficient
    system, but is not suitable for water piping
    under pressure inside buildings. The fittings and
    methods of joining are not dependable enough to
    trust against a leak that might occur inside a
    wall or an attic. But PVC piping is used
    extensively where piping is installed outside of
    habitable buildings.

  • Within the past several years a high strength
    plastic pipe has been developed that is suitable
    for high pressure water systems, and is approved
    by most building codes. The fittings are made of
    brass, and the connections by steel crimps. The
    major advantage of the material is that it is
    manufactured in long rolls, making installation
    easier because it eliminates many joints in a
  • Another advantage is that the material for cold
    water use is translucent white, and the material
    for hot water use is translucent red. The pipe
    also comes in blue. Material is manufactured
    under the name Wirsbo-pex. Wirsbo is a
    manufacturers name, and pex is a chemical
    acronym for polyethylene cross-linked, hence
    the X.
  • Water is transported through a system of piping
    by pressure. A common pressure available from a
    municipal system may be in the vicinity of 60
    pounds per square inch. In early times, the most
    economical way for a municipality to provide
    water pressure was to raise a water tank to a
    height of 100 feet or so, and the weight of the
    water would cause the pressure.

  • Consider that water weighs 62.4 pounds per
    cubic foot. Imagine a volume of one cubic foot, a
    block 12 x 12 x 12 high. Then divide the
    block into one inch x one inch columns, each 12
    inches tall. The cubic foot would consist of 144
    of these 1 x 1 x 12 columns of water.
  • How much would each column weigh? 62.4 divided
    by 144 0.433 pounds. Since the cross section
    area of one of these columns of water is one
    square inch, it follows that the weight of water
    transposes to 0.433 pounds per square inch, PER
  • Since unit pressure, or stress, is in terms of
    weight per unit of area, and the cross section of
    the column is one square inch, water pressure
    equals 0.433 psi per foot of height.
  • So what is the pressure of a one-square-inch
    column of water ten feet high? 0.433 x 10 4.33
  • What is the pressure of a one-square-inch
    column of water one hundred feet high? 0.433 x
    100 43.3 pounds.

  • Say you have a vertical pipe, 2 in diameter,
    10 high. What is the pressure at the bottom of
    the pipe? 4.33 psi.
  • What if the pipe were 4 in diameter, what would
    be the pressure in the bottom of the pipe? 4.33
  • It doesnt matter the volume of water per foot
    of height - - - unit pressure is in pounds per
    square inch. If the ocean were only one foot
    deep, the pressure at the bottom would be 0.433
  • Pressure is the force that pushes water through
    a system, from the point of origin, to the
    fixture that is farthest away from the source.
    Available pressure diminishes within the system
    for a variety of reasons first, it takes
    pressure to make the water meter work, so some of
    the available pressure is used to operate the
    water meter. Then, if the water piping rises in
    height, say from the water meter that may be 3
    below the ground, and the pipe extends upward to
    the attic space within a building, a portion of
    available pressure must be used to raise the
    water upward.

  • Then a portion of the available pressure must be
    used to operate a fixture, such as a sink,
    lavatory, or water closet. And finally, there is
    pressure lost in the system because of friction.
    Water moves against the walls of the pipe, and
    water movement must negotiate through bumps at
    fittings and valves.
  • All these contribute to the reduction of
    pressure from the source to a point of use.
  • Another aspect of properly sizing the pipes in
    a plumbing system is the speed at which water
    moves through the system. If water is allowed to
    move faster than about 8 feet per second, the
    movement will cause turbulence against the walls
    of the pipe, and through fittings. Turbulence in
    water flow creates NOISE.
  • In areas like West Texas, where the water
    contains a large amount of particulate matter,
    (calcium, magnesium, etc.) the turbulence will
    cause the particles to fasten themselves to pipe
    walls due to a difference in electrical charge.
    Over a period of time, particles build up in the
    pipe and reduce the effective diameter of the

  • Plumbing fixtures have evolved through
    improvements in design required by efficiency of
    use, and by some governmental regulations with
    purpose of conserving water.
  • Plumbing fixtures sinks, lavatories, closets,
    faucets, etc., are rated by water use in terms of
    FIXTURE UNITS. A fixture unit once was defined as
    one cubic foot of water, but that definition has
    no specific meaning in sizing piping. Fixtures
    defined by fixture units is a comparison of the
    amount of water used and these comparisons have
    led to the development of a chart defining
    gallons per minute demand, based on quantities of
    fixtures, and a reasonable assumption of
    frequency of simultaneous use of fixtures.
  • In other words, the more fixtures that are
    installed within a system, the less likely that
    all fixtures are used at the same time. So demand
    in gpm is less per fixture unit as the number of
    fixture units increase.

  • Standard plumbing fixture charts through
    history of use define the amount of fixture units
    per fixture, based primarily on their demand for
  • Two pages of the supplementary packet contain
    charts and tables that are useful as the basic
    components of water piping design.
  • First Chart (next slide)
  • Upper left gives maximum pressure required for
  • Lower right gives fixture unit value for various
  • Lower left gives pressure required to operate
    water meters.
  • Upper right gives the length of a straight piece
    of pipe that is equal to the amount of friction
    loss for various
  • fittings.

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  • There are two charts on the opposite side
  • Chart One is the conversion from fixture units
    to quantity of water in gallons per minute.
    Notice the chart has two double columns one
    labeled at the top for
  • Predominantly Flush TANKS, and to the right,
  • Predominantly Flush VALVES.
  • Valve types refer to the method by which water
    closets and urinals expel waste. Flush tanks are
    the domestic type, like in a residence, where
    water for flushing is stored in a tank at the
    back of the fixture.
  • Flush valves are the commercial type where
    there is no tank, and water for flushing must all
    come from the water supply pipes. This type of
    fixture requires more pressure and larger pipes
    to flush.
  • Notice in the conversion chart that as the
    number of fixture units INCREASE, the quantity in
    gallons per minute decreases proportionately.
    This is simply an indication that the more
    fixtures in a facility, the less likely that all
    will be required to flush at the same time.

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  • The second chart on the page is one that shows
    the relationship between available water pressure
    in p.s.i. per 100 feet, the flow of water in
    gallons per minute, the flow velocity of water,
    and the pipe diameter.
  • First, limit the flow of water to 8 ft. per
    second. That is indicated by a slanted line from
    upper left to lower right.
  • Then determine the available water pressure in
    p.s.i. per 100 feet from the piping layout. That
    will be a straight line upward from the bottom of
    the chart.
  • Where the two lines intersect will determine if
    the size of the pipe is based on available
    pressure, or by limiting the velocity of water to
    8 fps.
  • Diameter of pipe is indicated by a slanted line
    from lower left to upper right, and where this
    pipe diameter line FIRST intersects the pressure
    line or the velocity line, READING HORIZONTALLY
    TO THE LEFT, will be the maximum amount in gpm
    that particular pipe diameter will supply.

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  • An example problem follows, and shows a simple
    step by step procedure for determining the proper
    pipe size.

System is predominately flush TANKS
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  • In the process, two assumptions must be made,
    and will be verified later in the calculation.
    First, a meter size is not known until pipes are
    sized, so an assumed meter size must be selected.
    At the water meter chart, the total gpm for the
    system is known ( 20 gpm ) Find 20 gpm at the
    bottom of the chart and draw a straight line
    upward from the bottom. Probably the line will
    cross 2 or 3 slanted lines (that indicate meter
    size). Select the middle one and read to the
    left to see a pressure to operate the meter is 9
    psi for a ¾ meter.
  • Second, since pipe sizes are not known, the
    equivalent length of fittings must be assumed.
    The equivalent length of fittings is the addition
    of equivalent lengths for each fitting that is in
    the pipe that extends from the source of water to
    the fixture that is farthest away. Since this
    cannot yet be determined, ASSUME AN EQUIVALENT
    the measured length is 90 feet ½ of 90 45
    90 45 135 which is the CALCULATED length.

  • After subtracting the pressure loss of meter,
    rise, and fixture, an amount remains as the
    pressure that pushes the water through the
    system. But the pipe size chart needs a number
    that is the available pressure per 100 feet of
    length. Since an available pressure remains of
    31.67 psi, it must push the water a distance of
    135 feet. So pressure per 100 feet equals
    (pressure / calculated length) x 100.
  • In this case, 31.67 x 100 23.46 psi/100
  • 135
  • On the pipe size chart, draw a line from 23.46
    upward from the bottom of the chart and stop it
    at the 8 fps velocity line.

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System is predominately flush TANKS
  • From this little chart that is made to show the
    limit in gpm of water for each pipe size, go to
    the plan layout and write the sizes of pipes for
    each segment.
  • When you get to the maximum size of pipe at the
    meter, notice if it is larger than the meter you
    assumed. Chances are, the meter will need to be
    larger, which will result in LESS pressure
    required to operate. So the first assumption will
    be OK.
  • Last - - - list the types and sizes of fittings
    along the pipe that extends from the meter to the
    farthest fixture. Add the equivalent lengths to
    see if it exceeds 45, which was the assumption
    made for equivalent length of fittings.
  • If the added numbers are less than 45, then the
    second assumption is OK. If the number is larger
    than 45, then go back and recalculate the
    available pressure in psi per 100 ft., and
    recalculate the little pipe size chart.

System is predominately flush TANKS
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