General Questions Flashcards
What is the main purpose of an elevated storage tank
*Equalize the water pressure in the dis. system by properly locating tanks
*Eliminate the need for continuous pumping
*Minimize variations in water pressures due to short term shutdowns of power or pumps
*Provide a small amount of water for storage
*Reduce auxiliary power requirements
What are examples of distribution system changes that could change storage requirements and may require more tank storage
Major system changes such as large size main lines or the installation of multiple services, can change storage requirements and , any require more tank storage
How are instruments used to operate water supply systems automatically
By measuring water pressures throughout the distribution system and measuring water levels in service storage tanks.
When water pressures or levels drop below min. target levels etc
List 3 abnormal conditions encountered by operators of water storage facilities
Excess water demands
*Fire demands
*Broken/Out of service pumps, mains, or tanks
* Stale water
How are water levels controlled in storage reservoirs
Either manually or Automatically
*time clocks to operate valves or pumps
*altitude valves
Which water quality indicators may help you decide when a storage tank needs cleaning?
*Turbidities over an acceptable standard
*Excess color
*Tastes
*Odors
*Positive bacteriological samples
What is preventative maintenance
The repair or adjustment of equipment and facilities that is done before some type of deterioration takes place
What is corrective maintenance
Maintenance that is necessary when a problem already exists
What are the 2 methods used to clean storage tanks
Out of service - draining, washing, and disinfecting before service
In service - divers or robots (much less effective)
During what time of the year should a water storage facility be taken out of service for painting
During times of lowest water consumption -Oct-April
What is the guideline for determining whether chlorine gas or sodium hypochlorite is used to disinfect a water storage tank
Chlorine gas - large capacity
Sodium hypochlorite - small storage
What is the primary purpose of elevated tanks
To maintain adequate and fairly uniform pressure to a service area
Centrifugal pumps cannot operate unless the ________ is _________ in water
Impeller
Submerged
Chemical water quality problems can be caused by the ________ of chemicals from tank ________.
Leaching
Lining or coatings
In some areas where seasonal water demands become very _______, the chlorine residual in a storage tank may become ________ due to ______ detention time
Low
Depleted
Excessive
What information about equipment should be included in records
*date of install
*start up data
*failures
*any type of service performed etc
*results of tank inspection
*Condition of tank
*maintenance performed
*all repairs and corrective actiona
What safety precautions should be exercised when working around a water storage facility
1 area should be clean and clear
2 care should be taken when climbing ladders, stairways, wear ladder belts, ladder guards when not in use
3 test atmosphere and ensure adequate ven
A booster pump is used to ______ the pressure in the mains on the _______ side of the main ________ or to supply water to an elevated storage tank
Increase
Discharge
Pump
When a storage tank is to be taken out of service for maintenance, ______ and _____ are necessary so that the dis system will be able to meet the ______ of its customers
Coordination
Planning
Water demands
list 6 common types of storage facilities found in water supply systems
*Clear well
*Elevated storage tank
*Standpipe
*Ground level service storage res
*Hypo pneumatic / pressure tank
*surge tank
What is a clear well and it’s purpose
Used to store FILTERED water from a treatment plant. Will allow a filter plant to operate continuously at an average flow rate and place neither fluctuating nor excessive demands on the filters
Why should reservoirs be covered
To reduce the possibility of contamination
Regulator stations (PRV) are used for what purpose
To reduce pressure and maintain an even, acceptable pressure downstream from a high pressure system
What is the purpose of booster pumps
Used to increase the pressure in the main son the discharge side of the main pumps
or
to supply water to an elevated storage tank, also used to supply water to a service area at a higher elevation
What tasks do commercial divers perform during wet inspections
To maintain the interior of water storage tanks
- hired to inspect, clean, and repair without draining tank
Why is grounds maintenance importance
Leaves impression of a well run operation
Usually when a pump receives a signal to start, a light will come on in the control panel indicating that the pump is running. However, even when the pump light is on, what problems could possibly be occurring?
Even with the run light is on, the pump may not be pumping water
Install a positive flow report-backed signal device on the control panel to ENSURE pumps are pumping
How is a pump primed
*a special printer pump may be used to pump water into the pump casing and submerge the impeller
*a priming water tank or auxiliary water supply may be used to prime the pump by adding water to the pump casing and bleeding off the air
*hand-operated vac pump to remove air from pump casing causing water to flow into suction pipe
*foot valves
What conditions may require emergency maintenance and a water storage facility
*vandalism
*localized corrosion
*splits due to extensive metal loss
*stress failure in a plate or weld or structural collapse due to vacuum pressure
*high turbidity or bacteria from excessive sediment, annual contamination, or human contamination
What factors determine how long a coating on the outside of a storage tank will last
*depends on proper surface prep
*good, durable paint
*quality workmanship
*adequate dying and aging
*proper maintenance through periodic inspection and spot, partial, or complete removal of old paint and repainting as necessary
List 5 methods of corrosion control
*painting outside or inside
*metallic coating such as Zinc to protect the outside tank metals such as steel
*nonmetallic coatings to protect tank metals
*chemicals added during treatment of water to deposit a protective coating/film on tanks metal
*electrical control (catholic protection)
What is a common inhibitor
Any substance that promotes film formation on the surface to be protected when added to water
*lime
*soda ash
*caustic soda (sodium hypochloride)
What is the key to a successful catholic protection program
The replacement of the sacrificial anodes (usually made of magnesium or zinc) when they have been corroded away
Should be inspected at least YEARLY
List the 3 common types of disinfectants used to disinfect water storage facilities
Liquid chlorine (or gas)
Calcium Hypochlorite
Sodium Hypochlorite
What type of water level indicators could be damaged due to icing in a water storage tank?
Floats or electric sensors
What problems can be caused by ice buildup on the outside of an elevated tank reservoir
Can erode paint surfaces, increase the load on the structural supports, and create a falling ice hazard
What is the main function of a distribution storage facility
To take care of daily demands and especially peak demands
What do turbidity units measure in water systems
Cloudiness of water
What are the 3 types on maintenances
Preventative
Predictive
Corrective
In which areas of a storage facility should safety treads to be installed
Stairs
A regulatory station’s main function is to ______ pressure and to maintain an even _______ pressure downstream from a high pressure system
Reduce
Acceptable
What is the Time of Day pumping concept
Pumps are used only during the off peak hours of electrical usage namely during the hours between 10pm - 6am
What are the purposes of water storage facilities
Provide a sufficient amount of water to average or equalize the daily demand on the water system
Meeting the needs for fire protection, industrial use, and reserve storage
Storage facilities help maintain adequate pressures throughout the entire system
The selection of the type of storage facility or tank depends on what 2 factors
System’s individual needs
Type of terrain
New storage facilities and existing facilities that have been _____,______, painted, or had ______ installed must be disinfected before being placed into service
Repaired
Cleaned
Catholic protected
Many states require paint and _____ used in _____ water systems to be _____ by the state
Coatings
Potable
Approved
Why are inspections of water storage facilities conducted
It’s an important element of preventative maintenance
To determine the structural conditions of the storage reservoir, to identify any sanitary defects in the storage system, to evaluate the need for cleaning, to determine maintenance needs/effectiveness, and to identify any existing water quality problems
What are some benefits of distribution system storage
*Demands on the source of water, the pumping facilities, and the transmission and distribution mains are more nearly equalized and also the capabilities of the tanks and other treatment facilities in the system need not be so large
*System flows and pressures are improved and stabilized providing better service to customers in the area
*Reserve water supplies are provided in distribution system for emergencies such as fire fighting and power outages
List different types of control systems used to monitor water levels in storage facilities and also to start/stop pumps
*Electrodes (probes) mounted at various levels. Sense the rise and fall of the water level and start/stop pumps as necessary
*Ultrasonic signals, if signal is broken if covered by water
*Pressure switches - responds to changes in pressure
*Solid state electronic sensors - measure actual level
*Differential pressure altitude valves
What types of problems could operators encounter with electrodes (probes) used for sensing the rise and fall of the water level in a storage facility
*When electrodes need repair/replacement are difficult to reach
*May corrode or become contaminated, thus requiring replacement
How can the electric current and water surge be reduced when starting a centrifugal pump
By starting the pump with the discharge valve closed or throttled
List 4 possible causes of taste and odors in storage tanks and distribution systems
Settling and collection of sediment, rust, and chemical precipitates
Dust, dirt, birds, snakes, and other animals could enter the storage facility
High Chlorine Residual
List 4 possible causes of a positive coliform test result in storage tanks and distribution systems
Contaminated distribution system
Cross-connection
No or improper disinfection of new or repaired wells, reservoirs, or mains
Does the maintenance of concrete water storage facilities differ much from steel tanks
No - very similar
Vents/overflows properly screened
After 1st year and every other year after facility should be draining, cleansed, and inspected
What 2 points are critical to the successful operation of a booster pump
Installation & Alignment
What is the function of a gauge and how are gauges commonly used in connection with water storage facilities
Gauges measure pressure and can be useful indicator of water system pressures. Commonly used on the discharge side of pumps. Also used in the operation and maintenance of PRVs
Surge tanks are commonly used for what purpose
Necessary to control the problem of surges and water hammers. The surge tank should be located as close as possible to the activity that creates the water hammer.
One benefit of storing water in a distribution system is that system ______ and _____ are improved and stabilized, providing better ____ to customers in the area
Flows
Pressures
Services
Selection of a storage facility or tank depends on the system’s _____and the ____ where it will be installed
Individual needs
Type of terrain
How do surge arrestors protect piping systems from hydraulic transients
By controlling unusual velocity changes
Which type of storage facility is used for FILTERED water from water treatment plants
Elevated tanks
Where should a water system store nameplate data
With equipment records
What is an advantage of using surge control valves in a water dis system
Easy to fit into plant
Where should spoil or excavated material be placed in relation to the trench
*should be placed 2ft or more back from the edge of the trench
*only on 1 side of the trench
*between the trench & traffic
What water pressure is used for a leakage test
150 psi
50% higher than the normal expected operating pressure
List the basic requirements for a good pipe joint
Depending on pipe materials, conditions of installation, the degree of joint deflection (change in direction or alignment)
Pipe joints provide a water tight seal, easily installed, durable, and corrosion resistant
How can the storage of water in covered distribution reservoirs aid disinfection
Chlorinated water may be held in covered distribution reservoirs to provide an extended contact time for effective disinfection
What precautions should be taken with distribution reservoir drains and overflows
Cover with a fine mesh screen protect drains and overflows from cross-connections with storm drains, sewer lines, or other source of potential contamination
What type of material is commonly used for large water transmission mains
Concrete with a steel cylinder
What are 2 main uses of globe valves
Very efficient in either flow or pressure regulation
(Flow reg in larger pipes)
(Pressure reg in pipes 4” or smaller)
PRVs
High in friction losses, heavy, but unlikely to have sediment prevent completely closing
What is the main application of gate valves in a water distribution system
(Aka Linear stroke valve)
To isolate sections of mains to permit emergency repairs without interruption to service to a large number of customers
Why are valve boxes installed
To provide access to buried valves
Often made in two or more sections that telescope to give an adjustable length allowing the top of the box to be set at ground level
What problems could develop if a deep vault becomes flooded
Inadequate draining may result in a flooded vault and become a backsiphonage hazard
How many valves should be located at pipe crosses
Valves should be located on all branches from feeder mains and between mains and fire hydrants
3 valves should be used at pipe crosses and 2 at tees
How are valves open and closed
Manually or by actuators
Actuators is a device designed to power-operate the closure element of a valve. Controlled by water pressure or electronically
List the uses of fittings
*connect pipes of SAME size or DIFFERENT sizes
*change direction of FLOW
*STOP the flow
List the uses of hydrants
*Fight fires
*Flush pipelines
*Provide water to water trucks or other construction equipment
What are 4 major parts of a hydrant
*inlet pipe connection from water supply main
*main valve
*barrel
*the head
At what strategic points should meters be used
*On main supply lines/at pumping stations
*Reservoir outlets
*Connections to other utility systems
*Each customer’s service
How does metering reduce water consumption
By determining costs, metering prevents waste through EXCESSIVE use of water and thereby reduces water consumption
List the important stuff qualities you would look for when selecting a meter
Look for the ability to accurately measure and register the
*anticipated flow levels
*ability to meet required capacity with min head loss
*durability
*ruggedness
*precision of workmanship
*ease of repair
*availability of spare parts
Calculate the head loss through a meter in Ft if the possible loss is 15psi
(1 psi = 2.31ft)
15psi x 2.31 = 34.65 ft pressure loss
(Head loss)
What is the major difference between low-flow meters and high-flow meters
Low flow (Displacement) - commonly for customer service
-measures flow by registering the number of times the meter chamber (which vol is know) is filled and emptied
High flow (Velocity)
-measures the velocity of flow past a cross section of a known area. Meters are rugged and easily maintained
(Unreliable at low flow rates)
List the types of displacement meters and velocity meters
Displacement
- nutating disc
-piston
Velocity
-turbine
-propeller
-Venturi
-electronic
-insertion
Under what type of flow conditions are compound meters installed
When water flow FLUCTUATES widely
Examples where
-hotels
-hospitals
-factories
-schools
-apartments
-commercial properties
-office buildings
What are the 2 major types of electronic flow meters
Sonic meters - pulses sent alternately across pipe in opposite diagonal directions. Frequency of sound changes with velocity through which the sound waves must travel
Magnetic meter - water flowing through a magnetic field induces a small electric current flow that is proportional to the water flow
Fire lines may use what type of meter to measure flows
Proportional meters - a certain proportion of the total flow is diverted through a bypass meter and measured
What is a corporation stop
A water service shutoff valve located at the street main
What is a curb stop
A water service shutoff valve attached to the meter
Between the water service line and the customers home
Usually located near the curb between the water main and the building
How can mechanical damage of meters be avoided
By placing the meter behind the curb and in a meter box
Where are backflow prevention device normally installed when used
Normally installed at the service connection directly downstream from the meter
What factors should be considered when selecting a suitable backflow prevention device for a given situation
Depends on the degree of the health hazard, the probability of backflow occurring, the complexity of piping, and the probability of piping being modified
A pressure gauge on fire hydrant reads 75ft of pressure head. What is the pressure in psi?
75 ➗2.31 = 32.46 or 32.5psi
Explain the tapping procedure used for a wet tap
In a wet tap, you will bolt a valve to the tapping saddle; the actual drilling of the pipe through the valve can be done with the pipe still under pressure
Split sleeve; one half of the sleeve has opening with a flange or some other way for a valve can be attached. Fasten sleeve around pipe and make tight joint at each end. Fasten a valve size for proposed pipe extension to sleeve opening. Bolt tapping machine to the other end of valve. Open the valve, move cutter through the valve to the pipe, cut hole through pipe. Close valve, valve remains permanently in place and pipeline can become — need to find more info
What type of valve design is used in pressure-regulating valves
Glove design and have a spring-loaded diaphragm that adjusts the size of the opening
What is the purpose of blowoff valves
Used primarily for blowing off accumulated sediment from low spots in the line and for dewatering lines or reservoirs for repairs or inspections
What are the different types of valves
Ball (rotary)
Butterfly
Plug
Gate
Globe
Diaphragm
How can Asbestos-cement pipe be joined to other pipe materials
Special sleeve couplings
-Fit over machines ends
-Sleeved grooves to receive 2 interior rubber gasket rings
What problems can be created when air gets into water
Air tends to collect at high points in the lines forming pockets of air. Increases the resistance to slow by 10-15% or even air-lock and stop the flow of water completely
Air release valves can serve what 3 functions
Pressure relief
Valve protection
Other applications - altitude valves on supply lines to elevated tanks or stand pipes
How do you add a new main or lateral into an existing main where no line valve was installed
Cut a hole in the main using a tapping saddle or sleeve
During grinding and polishing work on a pipe, what safety precautions must be take
Safety goggles must be worn
What kind of underground lines should be located prior to excavation
Water
Sewer
Gas
Power
Telephone
Cable TV lines
Storm drains
List the different types of common shores
Hydraulic shores
Screw jacks
Air shores
Solid sheeting
Cylinder shoring
Shield shoring
List the 3 basic backflow prevention devices that are approved for the use at service connections
Air gap separation device
Reduced pressure principle (RPP) device
Double check valve
Sufficient water must be available from the water sources and distribution. Reservoir to _____, _______, and _____ supply the total requirements of all users under maximum demand conditions
Adequately
Dependably
Safely
Air gap separation or RPP devices are installed under what conditions
Areas where toxic substances are handled under pressure, the premise having auxiliary water supply may be contaminated
Wastewater treatment plants, wastewater pumping stations, reclaimed water reuse areas
Why are 2 check valves required for the double-check valve assembly and the reduced-pressure device?
Because the failure rate of a single check valve is much too high for reliable protection
2 check valves must be tested periodically and test cocks on the devices are required for this purpose
What is the distance of vertical gap in an air gap device
X2 the diameter of the discharge pipe, but no shorter than 1 inch
Why might a distribution system need to be oversized to meet fire demands
A fire can put a very high demand on a system for short periods of time
What determines whether transmission mains are short or long and whether the water is transported by gravity or pumping
Location of the source
Why should storage tanks be located in the center of use
To maintain adequate pressures even during periods of high demand
Why are storage pumps often installed in parallel
To serve relatively few customers located on very high or remote points
The basic requirements of pipes for water distribution systems are ____, ____, ____, and _____
Adequate strength
Durability
Maximum corrosion resistance
No adverse effects on water quality
Different types of joints are used to connect 2 lengths of pipes depends on the ____, _____, and _____
Pipe materials
Conditions of installation
Degree of joint deflectio
What is the first choice of methods to protect pipe from corrosion
Proper use of noncorrosive metals and mechanical coatings
When installing water mains parallel to sanitary sewers, what is the recommended min horizontal separation between the 2 pipes
10 ft
When installing braces or snow jacks, which one should be installed first
Top brace or jack
More info needed
Which type of valve has a moveable disc as large as the full diameter of the pipe
Butterfly valve
Where are pressure relief valves most commonly installed
On the side outlet of a tee at a specific point in the system
How can a distribution system avoid putting large areas out of service for repairs or replacement
Install valves in enough locations that relatively small parts of the system can be shut off
Which fitting are used to change the direction of flow in a dis sys
Elbows
Tees
Bends
One principal type of meter that will not interfere with the flow of water if the meter fails is the ______
Venturi meter
What is the main advantage of compound meters
They accurately measure flows from a fraction of a gallon to the normal capacity of the pipeline
Where does the service line to the customer’s system start
At the main with a corporation stop
What is one way to correctly size a meter on a service connection
The meter should be one size smaller than the service line
Which backflow prevention device provides the most protection
Air gap
What type of pump is commonly used in water dis sys
Centrifugal pumps
As pump efficiency varies with the load, two or more pumps are often installed in parallel enabling the number of pumps in operation to be varied, depending on the flow through the pumping station
What is the best source of power for dis sys pumps
Electric motors, and which are compact and well adapted to automatic control or remote operation
Dead-end water mains can cause what type of problems
Taste/odor water quality problems
Must be frequently flushed and should be avoided whenever possible
What is the main advantage of grid or loop water dis sys
Permit greater water flow to an area where there is a fire or other sources of high demand because the water is being carried to any particular location from more than one direction
List the forces water dis sys pipes must be capable of resisting
Exterior forces such as backfill cover over the pipe, the weight of the passing traffic, and other similar forces must be resisted.
Internal pressures = delivery pressure, surges, and water hammers
List the types of dis layouts
Tree - has dead ends
Loop
Grid
Shoring requirements depend on what factors
Depth of tench
Width of tench
Soil type
Soil conditions
Nearby activities - vibrations
Time of excavation - longer want heavier
What are the major causes of underground construction deaths
Lack of shoring
Shoring failure
How is the depth of a tench determined
Trenches must be deep enough that the pipe is protected from freezing, surface traffic, stream or river erosion, and possible future changes in the ground surface elevations
Generally, tench should be no more than 1-2ft wider than the outer diameter of the pipe
How would you check metal pipe for damage upon arrival at the job site and again prior to installation
Gently tapping each length of pipe with a hammer
If the pipe does not ring or hum clearly; the pipe is damaged and rejected
When water and sewer lines are not properly separated, what problem could develop
Present a contamination hazard if leakage from the sewer line saturates the soil in the vicinity of the water line
How can steel pipe be protected from corrosion
The inside and outside are protected with cement mortar, cold-applied mastic, or hot coal for enamel
Small pipe - galvanized
Pipe above ground - paint
How can the requirements for operational storage be reduced
With adequate operational storage, a small water treatment plant might be operated on only 1 or 2 shifts per day
How deep is the first layer of backfill
“Haunching” is from the bottom of the pipe, compacted up to the horizontal centerline (spring line) of the pipe
Where should trust blocks be installed
All tees, bends, caps, plugs, hydrants, or other fittings that change the direction of flow or stop the flow.
To prevent leakage or separation of the joint
How should pipes be prepared before they are joined together
Carefully clean the ends of the pipes and the joint materials and smooth out any rough edges
When laying pipe with a bell, the bell should point in what direction
Point the bells in the direction that the work is proceeding expect when the pipe is being laid downhill; then the bell should face uphill
How can operators be protected if shoring is not practical
Sloping excavation walls
Slope: 3/4ft —> 1ft up
What precautions should be taken when laying pipe on bedding
Bedding - material placed on the bottom of the trench to support the pipe
Brought up to grade with sand or soil to provide a suitable bedding
Couplings should not rest on, or settle down to, the original trench bottom and that the pipe is provided with an even bearing for its entire length
What are the responsibilities of a competent person at the excavation job site
Someone capable of ID-not existing and predictable hazards in the surroundings, or working conditions that are unsanitary/hazardous
Has authorization to take prompt corrective measures to eliminate the hazards
What are the components of a typical trench shoring system
Sheeting - solid material against soil
Uprights - supports sheeting |
Stringers - wales __
All trenches deeper than ____ ft must be shored
5 ft
Less than 4ft when examination indicates hazardous ground movement may be expected
How are the joint rings for concrete pressure pipe protected against external corrosion
The outside joint space is normally completely filled with cement mortar to protect the joint rings
Both the inner and out space is filled with mortor
What types of joints are used for PVC pipe
Solvent weld or bell and spigot
A gasketed joint is the usual type used for PVC pipe
List the commonly used corrosion - control techniques and materials for pipe protection
*nonmetallic pipe materials such as reinforced concrete and plastic
*nonmetallic coatings - coal for enamel, asphatics, cement motor, epoxy resins, vinyl resins/paints,
*metallic coating - zinc(galvanized), aluminum
*chemical treatment
*electrical control - cathodic protections
What types of joints are commonly used for Ductile-Iron pipe
Most often: mechanical & push-on
Also used - flanged, restrained, flexible. Sleeve
Why should existing lead service lines be replaced
These lines are no longer acceptable and should be replaced due to the potential for lead (toxic material) to enter the water
What are the most common materials used for service lines
Copper, PVC, PE, PB, or in special cases reinforced plastic pipe
Other materials also used - ductile iron, black and flavonoids wrought iron, steel, asbestos-cement, and brass
List the 3 types of plastic material used for plastic pipe
PVC - polyvinyl chloride
PE - polyethylene
PB - polybutylene
What is the primary function of temporary traffic control on streets and highways
Provide for the safe and effective movement of vehicles, bicyclists, and pedestrian, including persons of disabilities through and around TTC zones while reasonably protecting road users, workers, responders, and equipment
What publication is the national standard for all TTC devices used during construction, maintenance, utility activities, and incident management
US Dept of Trans
Manual of Uniform Traffic Control Devices
What are the disadvantages of asbestos-cement pipe
*Low flexural strength in small sizes (breaks when bent)
*vulnerability to impact damage
*difficult to locate buried pipes
*hard to thaw
*asbestos fiber has been known to leach out of the pipe in soft waters
List the major disadvantages of concrete pipe
*pipe is very heavy
*may be hard to tap
*needs special fittings
*may deteriorate in aggressive (corrosive) soils
What types of coating may be applied to steel pipe
Epoxy
Mastic
Galvanized
Protective wrap
Steel pipe may be liked with what types of materials
Epoxy lining
Exterior - epoxy or mastic
Galvanized
Plastic wrapped
How can the external corrosion of ductile-iron pipe be reduced
All pipe installed today is ductile-iron pile
Polyethylene encasement is used
PE
List the important installation features of water dis pipes
*Weight - lighter is easier to handle
*Jointing characteristics - flexibility, deflection
*Available sizes - alt size commonly used
*Ease of tapping the line
How can water quality be degraded in the dis system
*cross-connections
*time in system
*corrosion
*dead ends
*biological growth and activities
*age of facility
*high temps
*operational procedures
*unusual flows
Why should construction of dead-ends water mains be avoided
To prevent the development of tastes and odors
Any dead-end mains exceeding 1k ft should be constructed of pipe at least 6” in diameter. 2k ft 8”
Hydrant, flushing valve, or blowoff is needed at the end of each dead-end for periodic flushing
Why are booster pumps sometimes installed directly on mains
To increase the available system pressures.
Most systems, some pumping is required. Topography require reservoirs, elevated tanks, booster pumps to be installed
When _____ are out online or taken offline, _____ must be exercised so that ____ do not burst pipes due to _____ pressure or collapse pipes due to ____ pressures
Large pumps
Care
Surges
Excessive
Negative
Which substances in the water influences the rate of corrosion in a storage facility
Dissolved oxygen
During a distribution sys pressure test, a pressure gauge attached to a faucet in a home reads 30psi. What is the pressure head in ft
30 x 2.31 = 69.3ft
List the major parts of a water dis system
Pipes
Storage facilities
Pump stations
Valves
Fire hydrants
Meters
Other appurtenances
What determines the hydraulic adequacy of a dis sys
Determined by the pressures that exist at various points in the system under the conditions of operation
Water hammers can be caused by what actions
Result from turn pumps on or off or operating valves too rapidly
What conditions might cause thrust in a pipe
Water flowing in a pipe exerts thrust at any point where the layout of the system either changes direction of flow, increases velocity, or decreases/stops the flow
What causes friction losses in pipe
High hills, deep valleys - anticipated and corrected by design
Roughness of the interior of the pipe creating turbulence proportional to the velocity of water flowing in the pipe
What problems may be created by excessive pressures in a dis system
Pressures greater than 100psi will damage the customer’s facilities and plumbing fixtures
Why must a continuous positive water pressure be maintained in the dis sys at all times
To protect the dis sys from the entrance of toxic and other undesirable substances
Liquid chlorine piping systems must be closed because if moisture enters the system, it readily mixes with chlorine and forms ____, which will ____ the pipes, valves, joints, and fittings.
Hydrochloric acid
Corrode
What can cause a false positive chlorine residual reading when performing the DPD method
Precipitate
Care should be taken to prevent sharp bends in copper tubing because this will _____ and eventually the tubing will _____
Weaken it
Start leaking
Why do you not use wrenches longer than 6”, pipe wrenches, or wrenches with and extension to open chlorine container valves
You could exert too much force and break the valve
What should be done to the water supply pump when the hypochlorinator is shut down
Turn water supply pump off
How can provisions be made to allow recreation on water supply lakes and reservoirs without endangering water quality
Proper construction and location of recreation facilities such as boat ramp launching, boat harbors, picnic and camping areas, fishing, and open beach areas away from the intake area
Multi-level intake facilities (opening at several depths) because water can be drawn from depths where algal growths are not prevalent
What is stratification in lakes and reservoirs
Formations of separate layers of temp, plant life, or animal life
What problem can develop as transmission and storage facilities become older
*Gradual deterioration in protection against corrosion may lead to water quality problems
*Ruptures and leaks in piping become more frequent
Older pipes and facilities might have been poorly constructed when installed and perhaps had little or no protective coating even when new
How is water affected by length of time it remains in a distribution system
The longer the water is in the system, the more time is available for chemical and biological changes to take place
What problems can be caused by low flows
*Changes in water velocity and flow reversals can result in sediments being stirred up and carried along until they reach the consumer
*low circulation and stagnant water can result in growth of organisms, formation of sediments and corrosion products, depletion of O2, and increased tastes and odors
*turbulence can entrain air into the supply causing milky water, which is objectionable to consumers
What impacts does water temp have on distribution systems water quality
*Higher temps tend to speed the rate of chem reactions and increase biological growth rates
*Biological decomposition may be intensified by summer temps
*chlorine demands may be considerably greater so residuals will not carry as far in the distribution system in the summer
Which form of chlorine is most effective against biofilms
Chlorine is the most powerful disinfectant
Chloramines is most effective because they are more persistent in a distribution system and will eventually penetrate farther into the system for a longer time
Slime growths can cause what problems in distribution systems
Tastes and odors can be produced by slime growths of organisms that thrive on ammonia, iron, sulfide, and methane
Development of the iron bacteria, crenothrix result slime growth
Results in consumer complaints and accelerated corrosion and reduced flow from greater turbulence along the pipe wall
What is the most frequently reported cause of water-borne disease outbreaks in the US
Contamination resulting from backflow of unacceptable substances through cross-connections to Distribution systems
How can groundwater become contaminated or degraded
Less susceptible, but once contaminated takes a considerable time before they recover
Groundwaters may become contaminated or poorly constructed wells may contribute degraded water to the system
Degraded water may come from surface water moving about groundwater table
Leaching from nearby domestic, industrial, or Ag wastewater or passage through natural mineralized formations
