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PPT – WATER SUPPLY PIPING FOR BUILDINGS PowerPoint presentation | free to download - id: 5cd374-MzY3M

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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 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

water - 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

progression. - 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

system. - 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

FOOT OF HEIGHT. - 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

pounds. - 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

psi. - 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

psi. - 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

pipe.

- 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

water. - 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

fixtures. - Lower right gives fixture unit value for various

fixtures. - 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.

FITTINGS

FIXT PRESSURE

FIXTURE UNITS

WATER METER

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GLOBE VALVE

GATE VALVE

ANGLE VALVE

CHECK VALVE

- 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

LENGTH OF ½ THE MEASURED LENGTH. In this case,

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

feet - 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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- END OF FIRST DAY PLUMBING

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