1
Q
The two primary purposes of a distribution system
A
Consumption and fire protection
2
Q
Pascals law of hydraulics
A
Pressure exerted within a confined space results in equal pressure or force being exerted in every direction
3
Q
Flow (hydraulics)
A
The movement of a stream of water or other fluid from place to place
4
Q
Turbulent flow (hydraulics)
A
A flow characterized by random motion, mainly due to tuberculation and corrosion
5
Q
Laminar flow (hydraulics)
A
The movement of a liquid in a smooth, continuous, non-turbulent that does not necessarily mix
6
Q
Pressure meaning
A
The force exerted against an opposing body or thrust distributed over a surface. It is a force which tends to compress or move a body when applied.
(P = Force divided by area)
Usually expressed in pounds per square inch PSI
7
Q
Two types of gauges to measure pressure
A
Gauge pressure (psig) - pressure measured above that of atmospheric pressure
Absolute pressure (pisa) - pressure measured above that of a perfect vacuum. Where zero is absolute pressure 14.69psi
*when absolute pressure is requested and gauge pressure is known, add 14.69 to gauge PSI
8
Q
Head definition
A
The vertical distance, height, or energy of water above a reference point. A head of water can be expressed in either height (feet) or pressure (psi)
9
Q
Pressure Head
A
Measures the amount of energy in water due to water pressure
10
Q
Velocity head
A
Measures the amount of energy in water due to its motion or velocity
11
Q
Elevation head
A
Measures the amount of energy in water due to elevation
1psi =0.0689 bars 2.31ft of head OR 1 ft. Of head = 0.433psi
12
Q
Kinetic energy
A
The energy of water in motion
13
Q
Potential energy
A
The energy of water not in motion, example water behind a dam
14
Q
Arterial loop system (BEST)
A
Attempt to surround the distribution area with larger-diameter mains. The large mains then contribute water supply within the grid from several different directions
15
Q
Grid system (good)
A
Depends primarily on the fact that all mains are interconnected, so water drawn at any point can actually flow from several different directions
16
Q
Tree system (not good)
A
Brings water into an area with a transmission main, which the branches off into smaller mains. The smaller mains generally end up as dead ends. This is not considered a good distribution system design and is generally not recommended. In many cases, site specific conditions result in the selection of this type of system.
17
Q
Comprehensive maps
A
Provide overall view of entire system
500ft to 1000ft per inch
18
Q
Section plats (maps)
A
Shows various portions of system with more detail
50ft to 200ft per inch
Valve location, turns open and closed / main location
19
Q
As-builts (maps)
A
Drawings that show changes made during installation/repair
20
Q
Plan view (maps)
A
Show topographic view, pipe sizes, facilities, pressure zones, etc.
21
Q
Profiles (maps)
A
Shows elevations, hydraulic grade lines, station numbers, pipe diameter, velocity and rate of flow
22
Q
Service conditions (pipe material selection)
A
- Pressure (including surges and transients)
- soil loads, bearing capacity of soil, potential settlement
- corrosion potential of soil
- potential corrosive nature of some water
23
Q
Avability (pipe material selection)
A
- Local availability and experienced installation personnel
- Sizes and thickness (pressure rating & classes)
- Compatibility with available fittings
24
Q
Properties of the pipe (pipe material selection)
A
- Strength (static and fatigue, especially for water hammer)
- Ductility (ability to deform under tensile stress; the ability to be stretched)
- Corrosion resistance
- Fluid friction resistance (more important in transmission mains)
25
Economics (pipe material selection)
- Cost ( installed cost, including freight to job site and installation)
- Required life
- Cost of maintenance and repairs
26
Transmission mains
- Designed to carry large quantities
- Provide water to the distribution piping
- Generally long straight runs
- Services are not common
27
Distribution mains
- Carry water from transmission mains to residents and hydrants
- Many side connections
28
Factors in determining pipe size
Pressure, flow and velocity requirements
29
Consumer demand and fire flow
- average day demand: total usage for one year divided by 365
- per-capita water usage: gallons used each day
- maximum daily demand: highest 1-day/year
-peak hour demand: highest 1-hr usage
30
Cast iron pipe
- Early aas 1670’s
- Lead joints
- good flow characteristics
- Will shatter
31
Steel Pipe
- Lighter than iron
- High pressure & tensile strength
- Easily installed & jointed
- Lined w/ bituminous or cement
- bell and spigot lap welded joints
- catholic protection can be provided
32
Asbestos concrete
-made of asbestos fiber, silica sand, and cement
- strong, will not corrode, and high tensile strength
- abestos fibers can leach out of pipe and into softened water
- considered a hazardous materials
- connection with couplings with rubber gaskets
33
Ductile iron pipe
- used for high pressures applications
- strong, rigid, will resist bending, twisting without breaking
- lines w/bituminous and or polyethylene coating
- bell and spigot w rubber gasket
34
High density polyethylene (HDPE pipe)
- Thermal butt-fusion, flange assemblies or mechanical
- light weight and very durable
- high labor skill required
- relatively new product
35
Poly vinyl chloride, PVC pipe
- corrosion free, light & low cost
- good flow characteristics
- High tensile & impact strength
- hard to locate without a tracer
- needs special care on taps and bedding
DO NOT INSTALL NEAR GAS STATIONS
36
Concrete pipe
- steel cylinder, non/pre-stressed
-non-cylinder, not pre-stressed
- good corrosion resistance
- heavy and hard to move
- designed for high pressure
37
Zinc- epoxyed ductile iron pipe
- 200gm/sqm of zinc fr catholic protection (zinc acts as a sacrificial anode)
- 3mil epoxy coating
- no bituminous coating on exterior
- new production to US, most common in Europe
38
PVC pipe, c909
- 305psi rating
- corrosion resistant
- light, easy to move
- designed for high pressure
COPPER WIRE OR METALLIC TAPE FOR LOCATING
39
Earthquake resistant ductile iron pipe
- foreign and domestic manufactures
- 2% of contraction/expansion (2-3” per stick)
40
Pipe pressure rating recommendation
Should have a pressure rating 2.5 - 4 times the normal operating pressure
41
Under normal operating conditions water system flows
Should not exceed 5fps
42
Tensile strength
The resistance a material has to longitudinal, or length wise, pull before material fails
43
Flexural strength
The ability of a material to bend or flex without breaking
44
Class of pipe is referencing
The thickness of pipe walls and pressure rating
45
Spring line
The theoretical center line of a pipe
46
Flow line
The inside bottom of pipe or channel, also called invert
47
Hydraulic grade line
The surface or profile of water flowing in an open channel or pipe if partially full. If pipe is under pressure, the HGL is that level water would rise into a small, vertical tube connected to the pipe
A line joining the elevation that water would rise
48
Minimum desirable free available chlorine residual in water mains
Should be around 0.2mg/l
DPD-method is used to measure residual
49
Doubling the diameter of a pipeline
Will increase its carrying capacity 4-times
50
When the water in a main is at static (rest)
The water pressure will be at to highest point. As the water flow increases the water pressure will drop
51
Water mains parallel to sanitary sewers should be
Installed at least 10 feet horizontally and 1 foot higher than sewer lines
*joints more than 10’ft separation
52
Trunk line
Large pipe service as a supply main or feeder main in a water distribution system
53
Transmission main
A water main that transports water from main source or source to a distant area where water is distributed
54
Service line size (domestic service lines)
- Max. Water demand the customer will require
- main pressure under peak demand conditions
- excessive elevation & distance from main and high point
55
Galvanized iron pipes (domestic service lines)
- 2’ft lead goose connections corp. to service
- corrodes rapidly internally & externally
56
Copper tubing - K, L, M (domestic service lines)
- most popular to replace the old
- flexible, easy to install
- corrosion resistant in most soils
57
Plastic tubing (domestic service lines)
-cheap (4x less than Cu) and light
- harder to bend, makes install challenging
-does not have a good track record
58
Purpose of water storage facilities
- Design for adequate storage to meet high demands
- provide water for fire flow emergency
- provide contact time for disinfection (clearwell)
59
Types of storage facilities can be based on
- type of service
- configuration
- type of construction material
60
AWWA M42
Proper inspections cannot be conducted if sediment covers the bottom of the tank. Tanks should be washed out and inspected at least EVERY 3 YEARS, and where water supplies have sediment problems, annual washouts are recommended.
61
Operating storage
- Generally “floats” the system
The tank is connected to the distribution system,
* increased demand empties the tank
*decreased demand fills the tank
62
Emergency storage
- used mainly during high- demands fires
- installed in industrial areas for industries owned by fire protection (not normally used as potable sources)
63
Water stored for long periods of time could
- degrade in quality
- develop a foul tase and odor
- become unsafe
64
Water storage facilities can be located
At ground level or elevated
65
Elevated storage tanks
- generally supported by steel or concrete
- “float the system”
- altitude valves must be installed to prevent overfilling
66
Standpipes
- a tank that rests on the ground with a height greater than its diameter
- has both elevated water and large quantity of storage
- large amount of water needs to regularly be circulated through the tank
67
Clearwell storage
- treated water storage at treatment plant
- contact time for disinfection
- backwash water for filters
68
Hydropneumatic Systems
A system using an airtight tank in which air is compressed over water. The air applies pressure to water in the tank and the attached distribution pipelines
- minimize water hammer
- maintain constant downstream pressure
- reduces the frequency of pump start/stop
- 50/50 or 2/3 water 1/3 air
- provides water temporarily during pump failures
69
Surge tanks
- Prevents water hammer
- acts like a “spring”
70
Steel tank corrosion causes
- starts at the surface, moves inward
- warmer water = faster chemical corrosion reaction
- substances in the water (dissolved oxygen, minerals, low pH)
71
Steel tank corrosion control
- paint coating, metallic or non-metallic coating
- chemicals added during treatment, pH adjustment
- electrical control (catholic protection)
72
Langelier index
- positive = the water is scale forming
- negative = the water is corrosive
73
Corrosion coupon (steel pipe corrosion)
The piece of pipe removed during service install. Weight measured versus new pipe and if lighter = corrosion is happening
74
Galvanic corrosion
Use of dissimilar metals
75
Tuberculation
Development or formation of small mounds of corrosion products (rust) on the inside of iron pipe. These mounds (tubercles) increase the roughness of the inside of the pipe thus increasing the resistance to water flow (decrease c-factor)
Potential red water complaints
76
C- factor definition
Value used to indicate the smoothness of the interior of the pipe.
The higher = the smoother, the greater the carrying capacity
77
C factor - general numbers
140 = very smooth, all new pipe
120 = smooth, ordinary concrete
90 = slightly rough, brick sewers
60 = very tuberculated, iron or steel
78
Gate valves
Main function is for isolation or shut off purposes. A restricting disc is lowered into a seat which stops the flow of water
79
Rising stem gate valves
Well sites, fire protection services, and locations were cross-connection devices are installed
80
Non-rising stem gate valves
Underground applications on water mains and hydrant laterals
81
Butterfly valves
A valve consisting of a disk rotating on an axis across the diameter of a pipe to isolate or regulate the flow
- disc rotates on a spindle or shaft in only 1 direction
- 90 degrees to fully open
-gear box
- resilient seated
82
Globe valves
Used for regulating flow in a pipeline, consisting of a movable disk-type element or diaphragm and a stationary ring seat in a generally spherical body
83
Plug valve
Valves with cylindrical or comically tapered “plugs” which can be rotated inside the valve body to control the flow through the valve. The plugs in plug valves have one or more hollow passageways going sideways through the plug, so that fluid can flow thorough the plug when the valve is open
84
Check valves
A single acttion valve that closes to prevent backward flow of a liquid
- well discharge line
85
Foot valve
A self acting valve that allows water to flow in only one direction on the low pressure suction side of a pump operating under suction lift
- submersible well pump (maintains prime)
86
Altitude valve
Controls the high water level in reservoirs without the need for floats or other devices. It is a non throttling valve that remains fully open until the shutoff point is reached
87
Hydraulically pirated globe valves (CLA-VAL)
Pressure regulator valves
Speed control valves
Direction of flow (single and double action)
88
Air/vacuum release valve
-located at high points or summit
- installed above grade
-outlet screened
89
Blow-off valve
-located at low points/invert and/or dead-ends
-move stagnant water
-improve water quality
90
Corporation stop
Connected to the water main and the service line. It is the main shut off valve located under the street
Ball or gate valve
91
Angle meter (curb) stop
Connected to the service line and meter. It’s used to isolate consumers service.
Located in the meter box
92
Domestic meter selection
Usually one size under the service size and sized by RANGE OF FLOW REQUIREMENTS
Tested for accuracy about 5 to 10 years and replaced 15 to 20 years
93
Positive displacement types
Nutating - Disc
Piston - type
94
Nutating-disc meter
-very accurate in low flows up to 2”
-typical for residential and small businesses
-water flows though and the tilted disc rotates
Displacement meters can under register due to excessive wear
95
Piston-type meter (oscillating)
-Slightly greater head loss than nutating-disc
-Water flows into the chamber and displaces a piston and the oscillatory circulating motion is transmitted to a register
96
High flow / velocity / combo meter types
Turbo meters
Compound meters
97
Turbo meter
-The impeller is weightless in the water
- meters have an extended flow range with greater low-flows sensitivity
- they also have the ability to capture extended high-flow rates, all with virtually no wear on the meter
98
Compound meters
-low and high flows
-displacement and velocity type meter
-displacement part of the meter registers low flows, when head loss increases compounding valve is actuated and water flows through velocity portion of the meter
-head loss increases during high flows = less accurate then at low flows
99
Magnetic “mag”meter
Water flows though a magnetic field and small electric current which is relative to a measure of flow or water
100
Sonic meters
- sensors attached to sides of pipe
- sound pulses are sent alternating across the pipe diagonally
-measure of flow can be measured by using the difference between frequencies of the sound signal traveling with the flow of water and that of the frequency traveling against the flow of water
101
Pressure differential meter types
Venturi and Orifice plate
102
Venturi meters
-operate on pressure differential
-mainline flow applications
-large flows cannot be interrupted and/or friction loss may be effected
-pressure at throat and upstream from the throat are compared
-the difference is converted into gallons or cubic feet
103
Orifice Plate
-a plate with circular holes installed in between flanges on pipeline
- pressure a plate and upstream compared and converted to flow
104
Hydrant specifics
-Flow tests must maintain a minimum of 20psi
- Adequate pressure is 35psi min but preferred is 50-70psi
- Velocity 0.5 - 3.0 FPS with a max of 5 FPS
-18” min from grade to lowest opening on center
- minimum set back 2 feet from curb
- installed every 300-500 feet apart
105
Dry Barrel hydrant
-Typical for freezing environments
-Operating stem/nuts located on top
-Operating valve (auxiliary valve) at base
- Isolation valve located in street
- Drain valve at base
106
Wet barrel hydrant
- Typical where freezing is NOT an issue
- Operating nut/stem horizontal from opening
- Operating valve in the outlets
- Isolation valve located in the street
107
Blue hydrant
Class AA
1500 GPM or more
108
Green hydrant
Class A
1000-1499 GPM
109
Orange Hydrant
Class B
500-999 GPM
110
Red hydrant
Class C
Below 500 GPM
111
Pitot gauge
Used to check flows in the distribution system
112
Minimum water pressure in a water main
Should not drop below 20psi
113
Flushing velocity
Minimum velocity 2.5 fps but 3.5 fps is preferred
114
If water pressure drops below 5psi in a water main
Flushing and Coliform P/A bacteriological sampling is required in that area
115
Methods for cleaning pipes
-Pigging/ Ice pig
- Swabbing
-Scrapping
- Brushing
116
Air gap
A physical separation between potable and non portables services
Gap is 2x the diameter of the inlet pipe
117
Double check valve
Moderate risk for health hazard, does not protect from toxic substances
2- isolation rising stem gate valves
118
Pressure vacuum breaker
Very low protection
For medium strip irrigation systems
Not typical from normal irrigation systems
12” above highest point of use
119
Atmospheric vacuum breaker (AVB)
Typical for irrigation systems
Back siphonage only
12” above highest point of use
Non testable devices
120
Water audit
Consists of using listening devices and flow measurements to detect water losses
121
Peak demand
Is the maximum momentary load placed on a treatment plant, distribution system or pumping system
Expressed as a rate of GPM, MGD, AFD
122
Peak hour demand
The greatest volume per hour flowing through a treatment plant for any hour in the year
123
Maximum daily demand
Is the volume of water consumption used on the highest-consumption day in a year
124
Per Capita demand / Use rate
An estimate of water usage in a community, determined by dividing the total water used by the number of persons using it
Expressed in Gallons per capita/day
WWP Distribution Cards
flashcards
Decks in class (6)
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