Transcript Household Water - Physics @ CSU Stanislaus

Household Water
By:
Zoila Quiroz
&
Diana Chavez
Overview
 Terms
 Pascals
Principle
 Water Pressure
 Water Tower, Pumps
 How we get water into our home
 Pipes
 Experiment
 Closing
Terms:
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Pressure: defined by the equation
Pressure = Force / Area
Units
The units of pressure are those of force divided by the
units of area. The exact units depend on which system
you are using
In scientific units force is measured in Netwons (1 N = 1
kg m / s2) and area in m2. Pressure has units of N/m2
In Imperial units force is measured in pounds and area in
in2. Pressure has units of lbs/in2 (psi for short)
More Terms:
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Atmospheric Pressure: Atmospheric pressure is the pressure
exerted at the surface of a body by a column of air in an
atmosphere. The pressure varies both with altitude, and weather
patterns. Standard is an average atmospheric pressure at sea level,
and is defined as 1 atmosphere on Earth, equal to 760 millimeters of
mercury (760 Torr) and 101,325 Pascals.
1 atmosphere = 14.7 lbs/in2 = 101,000 N/m2 = 1.01325 bars = 760 Torr
= 32 feet of water
True Pressure: The total pressure exerted on a system equal to the
gauge pressure and atmospheric pressure.
Gauge Pressure: The pressure of a system measured by the gauge
which excludes atmospheric pressure
Pascal’s Principle
Pascal’s Principle: When a pressure is
applied to a confined liquid, that a
pressure is transmitted throughout the
extent of the liquid.
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Pressure exerted on an enclosed liquid is transmitted
equally to every part of the liquid and to the walls of the
container. (Pascal's principle)
A manometer relies on Pascal's principle to measure
pressure in gases.
Pascal's principle is important in understanding
hydraulics, the study of the transfer of forces through
fluids.
Water Pressure
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Water Pressure Explained
 As we turn on the kitchen faucet or start a bath, how the water is coming
out may not be something we think about. (Unless of course it is dripping or
not coming out at all!) But, water pressure is something that we should all
be familiar with. Most households receive water from a municipal water
system. In this method, the water is usually extracted from various
groundwater sources and then treated to remove impurities. Then, it is then
pumped to water towers, where gravity takes over to provide the pressure
that forces the water through pipes, and eventually to our homes. It is also
important to note that water flow is not the same thing as water pressure.
 Water flow is the result of your water pressure on the amount of water
available for delivery (volume). Low water flow could be a result of an
obstruction on the water line, and old pipe with contain mineral build-up or
corrosion that reduces the pipe’s internal diameter. So, if a water pressure
gauge is reading at an acceptable level but the pressure seems off, it may
be a flow problem.
How Do We Get Water in Our
Homes?
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Tower, Tank and Pump:
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A water tower is an incredibly simple
device. Although water towers come in
all shapes and sizes, they all do the
same thing: A water tower is simply a
large, elevated tank of water. Water
towers are tall to provide pressure.
Each foot of height provides 0.43 PSI
(pounds per square Inch) of pressure. A
typical municipal water supply runs at
between 50 and 100 PSI (major
appliances require at least 20 to 30
PSI). The water tower must be tall
enough to supply that level of pressure
to all of the houses and businesses in
the area of the tower. So water towers
are typically located on high ground,
and they are tall enough to provide the
necessary pressure. In hilly regions, a
tower can sometimes be replaced by a
simple tank located on the highest hill
in the area.
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In most towns, the water people
drink comes from either a well, a
river or a reservoir (normally a
local lake). The water is treated in
a water treatment plant to
remove sediment (by filtration
and/or settling) and bacteria
(typically with ozone, ultraviolet
light and chlorine). The output
from the water treatment plant is
clear, germ-free water. A high-lift
pump pressurizes the water and
sends it to the water system's
primary feeder pipes. The water
tower is attached to the primary
feeders quite simply, as shown in
this diagram:
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In a city, tall buildings
often need to solve their
own water pressure
problems. Because the
buildings are so tall, they
often exceed the height
that the city's water
pressure can handle.
Therefore, a tall building
will have its own pumps
and its own water towers.
Finally water arrives
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Water supply
The water supply system brings cold
water into the home under pressure.
The water is piped in through a main
supply line, usually from either a well,
spring or municipal water supply. If the
home has a water filtration or softening
system it is most effective when
positioned close to the point where the
water supply enters the home. After
entering the home, some of the water
is immediately diverted to the water
heater. At this point the hot and cold
branch lines are run to stub outs for
the various fixtures throughout the
home. Small supply lines, are used to
carry water from the stub outs to the
fixtures.
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The water heater is usually positioned
close to the point where the main
water line enters the home.
Pipes
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Why Pipes Burst
 When water freezes, it expands. That's why a can of soda explodes if it's
put into a freezer to chill quickly and forgotten. When water freezes in a
pipe, it expands the same way. If it expands enough, the pipe bursts, water
escapes and serious damage results.
 Surprisingly, ice forming in a pipe does not typically cause a break where
the ice blockage occurs. It's not the radial expansion of ice against the wall
of the pipe that causes the break. Rather, following a complete ice blockage
in a pipe, continued freezing and expansion inside the pipe causes water
pressure to increase downstream -- between the ice blockage and a closed
faucet at the end. It's this increase in water pressure that leads to pipe
failure. Usually the pipe bursts where little or no ice has formed. Upstream
from the ice blockage the water can always retreat back towards its source,
so there is no pressure build-up to cause a break. Water has to freeze for
ice blockages to occur. Pipes that are adequately protected along their
entire length by placement within the building's insulation, insulation on the
pipe itself, or heating, are safe.
References:
 www.howstuffworks.com
 www.weather.com
 www.lowes.com
 FriedHoffer,
BOB: Physics in the Home
 Betts, John: Essentials of Applied Physics