Distribution Network Components Flashcards
The primary purpose of a distribution network is to
deliver adequate volumes of safe drinking water
to system customers at adequate pressures.
Another important purpose of a distribution network is to
provide adequate fire flows to areas of the
system.
Components of Distribution Networks
Pipes
Storage Facilities
Pumps
Valves
Hydrants
Meters
Transmission systems are used to convey water from
system’s source of supply to the distribution
network.
Typical Characteristics of Transmission Systems
Large diameter pipelines
May be miles in length
Typically, no service connections directly from a transmission system
Water Mains and Related Equipment
Pipe Features Size
Distribution network pipes are normally sized to accommodate normal and peak system flows
and fire flows without adversely impacting water quality or resulting in an excessive pressure
drop.
Water Mains and Related Equipment
Pipe Features Material
Distribution network pipes are constructed of material that is durable and corrosion resistant.
Materials currently used for distribution network pipes include ductile iron, steel, concrete,
and plastic.
Materials often used for older pipes in a distribution network include cast iron, asbestos
cement, galvanized iron, and wood.
Water Mains and Related Equipment
Pipe Features Pressure Rating
The pressure rating of a pipe is a measure of the maximum normal pressure that a pipe is
able to withstand.
The pressure rating of a pipe will vary based on pipe material and pipe class.
What do Joints Do?
Connect two pipe segments.
Types of Joints
push-on, mechanical, flanged, mechanical couplings, sleeve, welded,
and harness or restrained sleeves.
What do fittings do?
Fittings can be used to connect pipes of the same or different size, change the direction of
flow, or stop flow.
Typical fittings include
sleeves, reducers, bends, tees, and caps.
Water main installation begins with…
…excavation. Excavation for water main installation is expensive
and dangerous.
Who has information and training that is recommended for excavation?
Occupational Safety and Health Administration (OSHA)
Preparations for excavation must be made in advance so…
the job will run smoothly, efficiently, and
safely
How many workers are killed each month in trenches?
2
Before excavation can begin
the project must be well planned and safety must be a
consideration.
To protect the trench and workers from traffic
the excavated material should be piled on
the pavement side of the trench.
Place all excavated or fill materials a minimum of…
wo feet away from the top edge
of the trench. If materials need to be closer than two feet from the edge of the
trench, install an effective barrier to prevent them from falling into the excavation.
Before entering the trench…
determine if shoring is necessary.
-OSHA requires a protective system for trenches 5 feet or greater in depth.
Normal oxygen levels range from…
19.5 to 21.5%.
Trenches 4 feet or more in depth must have…
a safe means of egress.
Spacing between ladders or other means of egress must be such that a worker will
not have to travel more than…
25 feet laterally to the nearest means of egress
Ladders must be…
secured and extend a minimum of 36 inches above the landing.
After the trench is prepared…
inspect, clean, and disinfect the pipe.
Inspect the pipe for…
defects, damage, oil, dirt, grease, and/or foreign matter.
Any unsound material should be…
replaced, and all foreign matter or dirt should be
removed from the interior of the pipe.
Swab the pipe with…
disinfection solution.
Before lowering the pipe into the trench…
the trench bottom should be smooth and free of material
like large stones or large dirt clods.
Before connecting the pipe:
-Inspect the bell,no dirt or foreign material is on the ring
-Clean the pipe end around the entire circumference from the end spigot to 1 inch above
the reference line
Once the pipe is cleaned, be careful gravel does not enter into
the line.
Be sure to use blocks or restraints to avoid…
leaks and pipe movement from the thrust against tees,
valves, bends, reducers and fire hydrants.
Size and type of the thrust block depends on…
maximum pressure,
pipe size,
kinds of soil
and
types of fittings.
1st layer of backfill
Only clean sand or selected soil
Bedding around the pipe should be…
of uniform size and material.
The first layer of backfill should be placed…
both sides of the pipe, up to about the
center of the pipe.
Haunching is…
Compacting the first layer of backfill around the pipe
The backfill material should be compacted a what intervals?
12
inch intervals to minimize settlement.
Backfill practices vary depending on…
pipe,
local soil conditions
regulatory
requirements
Improper compaction =
broken lines
Large backfill =
increase probability of main break
After the trench has been backfilled, the new main must be…
pressure tested to determine whether
there are any leaks
The pressure test may be performed…
one section at a time between valves or the installer may wait
and test the entire job at one time.
What PSI is the pressure tested at?
150 PSI
How long is the pressure tested?
should last for 1 to 2 hours.
How our lines pressure tested?
connecting a test pump to the new main and slowly increasing the pressure to
reach 150 psi.
How much of a loss in PSI during a pressure test would fail?
5 psi,
All new sections of water mains must be thoroughly…
disinfected.
Water suppliers must adhere to _______ when repairing or replacing water mains to ensure water quality is not compromised.
American Water Works Association (AWWA) Standard
C651 w
What are 2 examples of disinfecting new water mains?
Calcium hypochlorite tablets placed in each section of pipe and fire hydrant as
work progresses.
A concentrated chlorine solution injected through a corporation stop.
The chlorination rate should be such that it will produce a concentration of…
50 mg/L
when mixed with incoming water.
The chlorine solution should remain in the pipe for at least…
24 hours.
At the end of the contact period, the chlorinated water should be…
flushed from the pipeline.
Flushing a new main after disinfection should be done at a velocity of…
5 ft/s is
obtained in the pipe
How long should the velocity be held at when flushing a main after disinfection?
This velocity should be maintained long enough to allow two or three complete
changes of water and for the water to run visibly clean
Gravel in the line is an indication of
improper installation.
Chlorinated water cannot be…
discharged directly to surface waters or to
storm sewers.
To discharge potable water to a stream or storm drain, best management
practices for
dechlorination must be followed.
Prior to any discharges,
the DEP Clean Water program must be
notified.
Example of dechlorination during flushing
hydrants can be outfitted with
dechlorination devices, which hold tablets typically made of sodium sulfite or ascorbic acid
for dechlorination.
After a new pipeline has been disinfected and flushed, it should be
refilled with water from the
distribution system and tested for bacteriological quality.
the proper sequence for putting a new main in service is…
repair
backfill
pressure test
disinfection
flushing
sample for bacteria
Service lines are used to…
convey water from the distribution network to individual system
customers
Typical materials used for service lines include…
plastic
copper
steel
iron
lead
Lead service lines are being…
neutralized by corrosion control practices
are being removed from
service
A corporation stop or shut-off valve is typically located at
the connection of the service line and
distribution pipe
Corporation stop are typically tapped at
10:00 o’clock or 2:00 o’clock positions.
An additional shut-off valve that is typically located along the service line, near the
customer property line.
the curb stop
The customer meter used for billing purposes is located on the…
downstream side of the curb unit
stop.
Customer water meters are usually located…
indoors in basements
shallow outdoor meter pit/box
Backflow prevention devices – where required - are installed at
between the
meter and the customer’s line to prevent contamination of the distribution network from potential
backflow.
Storage tanks help offset…
fluctuations in demand
Storage tanks help minimize…
fluctuations in system pressure
Elevated tanks are used to
provide pressure in distribution systems
Storage facilities provide…
reserve volumes of water to help meet fire flow needs
Provide an emergency source of supply for the system.
Define Flow
the volume of water per unit of time that passes through a pump. Typical units of measure
for flow include gallons per minute (gpm), cubic feet per second (cfs), and gallons per day (gpd).
Define Pump Head
the amount of energy input to the water by the pump. Pump head is typically
measured in units of feet of water (ft)
How tall must a column of water be to provide 1 PSI?
2.31 feet
Define Water Horsepower
the amount of power supplied to the water which is needed to pump water to
a certain elevation. Water Horsepower is typically measured in units of horsepower (hp).
Define Brake Horsepower
the amount of power that must be applied to the pump shaft to operate the
pump.
Brake Horsepower must be higher than water horsepower bc…
inefficiencies in the pump and
motor, where energy is lost to friction and heat.
Define Pump Efficiency
the percentage of the power input to the shaft, that is actually transferred to
the water.
Typical pump efficiencies can range from…
50 percent to 85 percent depending on the
size and characteristics of the pump.
Water Horsepower Calculation
efficiency = power output/power input
or
water horsepower = efficiency x brake horsepower.
Purpose of Valves
The primary purpose of valves is to allow for isolation of mains or sections of main within the
network.
Another important function of valves is to control flow or pressure.
Isolation Valves are used to…
isolate
mains or sections of mains
solation may be necessary when…
repairing main breaks/leaks
performing other distribution network
maintenance activities.
The most commonly used isolation
valve is…
gate valve
Gate valves
should NOT be used to…
throttle flow.
Gate valves should be operated…
periodically through the full
open/close cycle (valve exercising)
to keep them operable.
Control Valves are used to…
control flow or pressure in an area of the distribution network.
Flow control valves can be used to…
throttle or limit flow
change flow direction
prevent revers flow
Examples of flow control valves
butterfly valve
check valves
backflow prevention valves
globe valve
altitude valve
Altitude valves are types of flow control valves that control flow in and out of…
storage
facilities based on water level
Altitude valves work by…
water level, when the tank reaches max level, valve closes
when tank drops the valve opens
Pressure control valves can be used to…
reduce pressure
maintain pressure
protect against
overpressure
pressure reducing
valves
reduce pressure
pressure
sustaining valves
maintain pressure
pressure relief valves
protect against
overpressure
Pressure reducing valves are used to
create
“break” pressure to
keep system pressures less than the
pressure ratings in pipes and to avoid
other adverse impacts of high pressure.
Air Release Valves are used to
eliminate air from a distribution network or to allow air into a
distribution network.
Air relief or air release valves
relieve
pockets of air which typically accumulate
at high elevation points in a distribution
network.
Vacuum relief valves allow
air into the
distribution network to protect the system
against low pressures
Vacuum relief valves are
commonly used along…
transmission mains
and at the discharge of pump stations
Vacuum relief valves protect against…
low pressures that can
occur as a result of sudden large changes
in flow velocity.
Air relief and vacuum release valves are
employed typically on
higher capacity
transmission pipelines that don’t typically
supply customer service connections that
act to discharge air
Isolation valves should be located
in a manner that will limit service interruptions during
emergency repairs and general maintenance
General rule of thumb regarding location of isolation valves:
isolating a segment of main
should require operation of no more than 4 valves.
Check valves are used in distribution systems to
prevent backflow
Check valves allow flow in
only
one direction.
Valves can be operated
manually
or
automatically via control systems
Gate Valve #of turn Calculation
of turns = (Dia.Inches x 3)+3
The proper direction to open the valve is usually indicated by
arrow on the valve bonnet.
The direction (clockwise or counter clockwise) used to open or close a valve can…
vary from valve to
valve.
When exercising a valve, the operator should make sure that a valve is properly
returned to its
original position by counting the number of turns
When exercising valves, be aware
water hammer
Water hammer is
the momentary increase in pressure inside a pipe caused by a sudden
change of direction or velocity of the liquid in the pipe
Water hammer can cause
pressure spikes 10 times higher than normal operating
pressures.
Water hammer can be particularly dangerous because
the increase in pressure can be
severe enough to rupture a pipe or cause damage to equipment.
Avoid water hammers by…
slowly open and close valves.
Meters
measure, display, and record the amount of water that passes through a distribution system
component.
Typical applications of meters in a distribution network include:
Measuring the amount of water
Measuring the amount of water supplied to a particular area of the system
Measuring the amount of water used by a customer,
Monitoring Non-revenue water in a distribution network.
Types of Meters
Displacement Meters
Velocity Meters
Compound Meters
Solid State Meters
Proportional Meters
Displacement Meters
Commonly used as single-family and
multi-family residential service meters.
Typically have diameters of 2-inches or
less.
Generally used to measure low flow rates.
Have limitations at very high flows.
Velocity Meters
Commonly used in pump stations,
industrial facilities, and large diameter
mains to measure high rates of flow.
Do not accurately measure low flow
rates.
Include the Venturi, Turbine, and
Propeller type meters.
Compound Meters
Commonly used to measure flow at
apartment complexes, schools, and
industries that can typically have high
peaks in water use compared with daily
averages.
. Two meters in a single assembly; with a
positive displacement meter measuring
low flows and a turbine meter measuring
moderate to high flows.
Used to me
Solid State Meters
Measure flow magnetically (magnetic
meter) or sonically (ultrasonic meter).
Highly accurate if properly located.
Most water meters should be installed in a
horizontal alignment in the upright
position. Mag meters can be installed in a
vertical alignment, but only with flow
moving in the upward direction.
Proportional Meters
Measure high flowrates at locations such
as fire service lines.
Do not measure low flows accurately.
Purpose of Fire Hydrants
extinguishing
fires.
flushing pipelines in the event of taste and/or odor complaints.
supplying water to water trucks and construction equipment.
Types of Fire Hydrants
Dry-barrel hydrants
Wet-barrel hydrants
Dry-barrel hydrants
nclude a shut-off valve and drain. The drain is open when the
hydrants main valve is fully closed (otherwise the water left in the
barrel once the main valve closes cannot escape and might
freeze).
Wet-barrel hydrants
Will always be charged (have water in the hydrant). Have a shutoff valve at the outlet and can only be used in areas where
freezing is not a concern.
Hydrants generally have three nozzles
Two 2 ½-inch nozzles
One 4 ½ -inch nozzle
Protective caps for the nozzle heads are necessary to
to safeguard the nozzle threads.
Typical fire flow needs a minimum of…
500 gallons per minute (gpm) for low density residential areas
to 3,500 gpm or more for areas with large or high occupancy facilities.
Fire companies need to be able to quickly determine…
They need to know how much water is available from the closest hydrant.
The water pressure in each hydrant.
NFPA Hydrant Coding Blue
1500 or more Very good flows
NFPA Hydrant Coding Green
1000-1499 Good flow for residential
NFPA Hydrant Coding Orange
500-999 Marginally adequate flow
NFPA Hydrant Coding Red
Below 500 Inadequate flow
Locations of Fire Hydrants should be
easily accessible and 300 to 600 feet,
depending on the area served.
Before installing a new hydrant,
test the hydrant by opening and closing to ensure no damage
occurred during storage or shipping.
Also, before installing a hydrant,
ensure that the hydrant meets local standards.
Most hydrants open..
counterclockwise and have operating nuts that measure 1 ¼ in.
The breakflange of a hydrant should be…
2 inches above the ground surface
Hydrants are typically located at street intersections so…
a hose can be strung in any direction for
flushing.
Hydrants should be located far enough back from a roadway to
minimize the danger of
being struck by vehicles.
When installing a hydrant, a hydrant must be set on
firm footing that will not rot or settle (flat stone or concrete slab is ideal)
Hydrants must also be securely…
blocked or restrained from movement because the force
against it will be tremendous if the valve is closed too quickly.
To facilitate quick removal of the water from the hydrant barrel when the main valve is
shut,
a pocket of coarse gravel or crushed rock (e.g., 2B stone) should be placed in the
excavation before the hydrant is set
The gravel or stone for a hydrant base should …
start at the bottom of the trench and continue to at
least 6 inches above the hydrant drain.
It is good for a water utility to have a written policy that defines the permitted use of…
fire hydrants, and
identify unpermitted or unauthorized use, and the consequences for violating this policy
Fire Hydrant Operation Tips
-always stand on the side without a cap
-count number of turns
-slowly operate
-regulate flow through nozzels
-exercise once a year at least
Define Blackflow
is the flow of water, or mixture of water and other substances, from a source other than
an intended source into the distribution network.
Backflow can occur when…
when the pressure at the
unintended source, often a customer connection, is greater than the pressure in the distribution
network.
Purpose of Backflow Prevention
To prevent potential contaminants from being introduced to the distribution network by the reverse flow of
water from a source of questionable water quality.
Types of Backflow Prevention Devices
A physical air gap
A reduced pressure device
Vacuum Breaker
A double-check valve assembly
Pressure
he force per unit of area. usually PSI
Pressure Head
the vertical distance from a free water surface to a point below the surface
Pressure head is commonly expressed in
units of feet
of water
The volume of water does not matter as the pressure is
measured in pound per square inch increments at the base of the unit.
Relation between Head and Pressure
psi = pressure head, ft/2.31
or
pressure, psi x 2.31 = Pressure head, ft
Hydraulic Grade Line (HGL)
the height to which a column of water will rise if you placed a
vertical riser pipe on a pipe under pressure.
Energy Loss is
the difference between the hydraulic grade line at 2 different points, one upstream and one downstream
Friction Losses
As water travels through a pipeline, the energy or head of the water is reduced as turbulence in the
water increases due to friction created by the roughness of the pipe walls.
Friction loss in a pipe depends upon the
velocity (rate of flow)
pipe size (diameter)
length of pipe
roughness inside
The degree of pipe roughness is called
C-Factor.
The C value is derived by
using the Hazen-Williams equation which relates the flow of water in a
pipe with the physical properties of the pipe and the pressure drop caused by friction.
The higher
C values
represent smoother inside surfaces of the pipe.
The pipeline roughness varies based on…
age
material
size
quality of water
Tuberculation in the pipes can cause
a substantial increase in friction loss, and can also
significantly reduce the effective diameter of a pipe
Loss in diameter of pipe by tuberculation can…
decreases the carrying
capacity of the pipe as well as reduces the available pressure in the pipeline.
if the flow in a pipeline is doubled, the head loss/pressure drop will…
increase by a factor of about 4
Head loss caused by rapid changes in velocity due to:
Changes in pipe diameter, shape, or direction, or
Meters and valves.
Define Consumption
actual (metered) or estimated water uses within a distribution network.
Define Unaccounted-for Water (non-revenue water)
as water that is produced, but not billed due to utility policy (unbilled authorized
consumption like fire hydrant flushing) and real (leakage) losses; and water that is inadvertently
under-billed due to apparent (customer) losses from customer meter inaccuracies, billing system
error, or unauthorized consumption.
Define system demand
is the total volume of water supplied to the distribution system including
customer consumption (billed and unbilled), as well as system leakage and unauthorized use of
water from fire hydrants, commonly quoted in gallons per day (gpd), or million gallons per day
(mgd).
Residential customers
include residential or domestic establishments. Residential customers can
also include apartment complexes and mobile home parks.
Commercial customers
typical commercial businesses, including stores and office
buildings.
Industrial customers
include larger facilities such as industrial plants and warehouses.
Other commonly used customer category types include…
institutional
bulk
municipal
Diurnal Demand
Curve
relatively low during the night when most people are sleeping compared with
demands in the early morning hours when people wake and prepare for the day.
peak morning and evening hours
Summer demands are usually relatively
high compared to demands in the winter due to additional
summer water uses such as irrigation.
Distribution network components are typically sized to
meet these peak demands.
During periods of high demand system pressure will
drop during high periods of demand
Adequate positive pressure should be provided throughout a distribution network to ensure…
adequate water
service and protect the system against backflow.
The main purpose of elevated tanks in water distribution
systems is to…
to sustain sufficient pressure in the system while water demands vary.
Typical acceptable working pressures range from:
35-100psi
PA Code, Chapter 109 – limits normal pressure to
no less than 25 to no more than 125 psi
PA Code, Chapter 109 – limits peak demand pressure to
20-150 psi
System pressure below 20 psi could experience
backflow conditions which could impact water quality.
Pressure zones in waster system
typically separated by pumps, pressure control valves, and isolation
valves.
seen when there is a wide range of elevation
Water distribution network pipelines are generally sized to
meet peak demands, including fire flows.
Fire flow needs typically range from a
minimum of 500 gallons per minute (gpm) for low density
residential areas to 3,500 gpm or more for areas with large or high occupancy facilities.
Surges are…
short-burst increases in pressure (“pressure spikes”) in the distribution system
Surges are caused by…
opening or closing valves or fire hydrants too quickly, pumps suddenly deactivating, or similar upsets that
rapidly change flow velocities in the water distribution system.
Other names for a Surge
Water Hammer
pressure transient
surges cause
Pipe bursting,
Pipe collapsing, or
Failure of other distribution network components.
Preventative Measures for Surges
Proper operations, including slow opening and closing of valves and hydrants.
Use of pressure surge control devices such as pressure and surge relief valves, vacuum
relief valves, and surge tanks.
5 Maintenance Programs in Distribution Network
Pump
Valve
Meter
Fire hydrant
Inspection/Monitoring
Every system should have a regular program to inspect and maintain pumps including…
Clean the pump and motor
Check condition of impeller, bearings, seals and alignment of couplings.
Visual inspection for excessive noise, vibration, heat and odor.
Consult manufacture for complete list of maintenance items and methods.
When should valves be exercised and inspected?
at least once per year
Valve inspection includes
verify location/label # on map
remove cover inspect stem
operate vavle
listen with leak detection
record condition
clean replace missing lids
place the valve back to its OG position
When you close the valve, paint a
C
when you open a valve
paint a O
Manual air releases should be…
opened and flushed to remove
accumulated air, at least twice per year.
Automatic air release, vacuum breaker, or pressure-reducing valves should be inspected
at least
every six months
The accuracy of a water meter may decrease over time due to
wear, water deposits, or turbulence
When establishing a meter testing program, the following issues should be considered:
Age of meter,
Water use, and
Water quality.
Cost of testing and/or replacing meters
Meter Test procedures vary based on
meter type and can be obtained from the meter manufacturer.
Annual Inspection and Operation of Fire Hydrant
Can be performed efficiently in conjunction with pipe flushing.
Inoperative hydrants should be noted and tagged.
Routine inspection and maintenance of the distribution network should include:
Daily inspection of key components such as storage and pumping facilities.
Make sure that hatches and gates are locked.
Access to distribution network components should be restricted to water system personnel only.
three key components of a pipeline maintenance program.
leak detection
main break repair
pipeline replacement/rehab
Common methods of leak detection include:
Direct observation,
Use of acoustic equipment e.g. geophones, devices using amplifiers to boost sound such as
ground mikes, and other listening devices, and correlators to help pinpoint leaks.
Flow Measurement - Measuring flows into small zones of the distribution system known as District
Metered Areas (DMA).
If nighttime flows into a DMA slowly increase over several days
a newly
emerging leak is likely occurring, and leak detection activity should be assigned in this area of the
water distribution system.
Main breaks are caused by
unbalanced forces exerted on a pipeline, which may result from events such as
subsidence, earthquake, and freeze/thaw cycles.
Detection of Main Breaks
Physical observations.
Customer complaints of low pressure.
Observation of non-typical system records
Main Break Response Steps
Locate
811 Call
Preliminary Assessment (how to isolate/impacts on customers)
Isolate
Expose
Pressure test
disinfect
flush
test for bacteria
return main to service
record
If there is a loss of positive water pressure that is caused by a main break,
repair or replacement and the operator sees evidence of contamination or he suspects a high
risk of contamination…
DEP should be notified within 1 hour of this investigation. Water
supply personnel should follow DEP’s “Policy for Determining When Loss of Positive
Pressure Situations in the Distribution System Require One-Hour Reporting to DEP and
Issuing Tier 1 Public Notification.” (393-2129-003)
Remember, any excavation over 5 feet deep
requires shoring to insure the safety of
personnel entering the trench.
To minimize the risk of contamination when repairing a break…
consider making repairs under system pressure
with the water flowing.
Reports and records of main breaks should be used to
assist in prioritizing water main
replacements.
Areas where main breaks are a regular occurrence should be
scheduled for
replacement.
If the trench is long
enough to warrant it, safety ladders for exiting the trench should be no more than
25
feet apart
f multiple lengths of pipe are to be replaced, make sure the new pipe is inspected to be
free of
debris before it is inserted.
bell-and-spigot piping normally has ___
Marks for indicating the proper insertion
depth on each length
make sure the gaskets are properly placed so they are
not twisted
or chipped.
Another tool for preventing pipe movement is _______ . They are
placed on bends where pressure surges might cause the pipe to move.
thrust blocks
The bedding around the pipe should be of
uniform size and material.
Allowing materials of various sizes such as large rocks could
cause the pipe to
fracture during settlement.
Backfill material should be compacted at
_______ intervals to minimize settlement.
1 ft
Non Structural Methods of Pipeline Rehab.
cleaning
lining
Cleaning and Lining water mains will
hydraulic capacity of pipelines
Cleaning and Lining water mains will NOT
improve the structural integrity of the pipe
and will not address a problem of recurring water main breaks if this exists within the pipeline.
Structural Methods of Pipeline Rehab.
structural liners
sliplining
pipe-bursting
Structural Methods of Pipeline Rehab will
improve the
structural integrity of the pipeline and often result in a new pipe within the existing host pipe
Trenchless pipeline rehab does not
require full pipe excavation.
Drinking water distribution networks provide
adequate supplies of safe drinking water and fire
flows to areas of the system.
Transmission systems typically have
large diameter pipes and no direct connections to
customers.
Distribution storage tanks help
offset system demand fluctuations.
Typical pump efficiencies can vary from
50 to 85 percent depending on the size and
characteristics of the pump.
Valves are used to isolate sections of water mains and to
control flow and pressure.
Dry barrel hydrants are used to
prevent damage from freezing.
Backflow protection helps to keep
harmful contaminants from entering the distribution network
The three primary functions of distribution storage facilities
Equalize Demands
Minimize fluctuation in system pressure
Fire Protection
Emergency Supply
The larger the tank volume
more stable the pressures in the distribution system despite
fluctuations in demand or changes in pump operation.
Types of Storage Facilities
Clear well
Elevated
Ground Level
Stand pipe
Hydropneumatic
Clear well
often used for storage of treated water at a treatment facility
Elevated Tank
The main purpose of elevated tanks in
water distribution systems is to sustain
pressure in the system while system water
demands vary.
Ground Level Tank
constructed at or below ground level.
Ground level storage facilities are generally less expensive to construct and easier to maintain than
elevated storage facilities. Occasionally, pumps are used to maximize the useable storage volume
in ground level storage facilities.
Stand pipe
If the tank is significantly taller than it is wide, it is usually referred to as a standpipe.
Hydropneumatic Tank
(Pressure Tank)
are used to
regulate and maintain water pressure and promote more efficient
pump operations in these areas. Pressure in a hydropneumatic
tank is controlled by the volume of air in the tank relative to the
volume of water.
Useable Storage
e is the total volume of water in a storage facility that can provide minimum required
pressures to the highest elevation customers who are served by the facility.
3 Primary Distribution Storage Functions
Equalization Storage
Fire Storage
Emergency Storage
Equalization Storage
provides storage for the
equalization of system demands and
pressures. It is designed to handle the normal
daily fluctuations in water level in a storage
facility due to peaks in system demand.
Fire Storage
A reserve volume of water to help meet system
fire flow needs. T
Emergency Storage
A reserve volume of water to help meet system
supply needs during an emergency event.
The operation of the distribution pumps and subsequent refilling of distribution
storage can also be controlled by
pressure
pump speed
flow rates
time of day
The operation of distribution pumps is often controlled by the ______ ______ in a storage facility
Water Level
Emergency Refill
Secondary or lag pumps are typically operated to refill system storage following excessive peaks in
demand or emergency conditions, such as a fire or a main break.
Types of Storage Level Controls
Level Recorders
Control Valves
Pump Controllers/SCADA systems
Level Recorders
In order to maintain proper operations, the water level in a storage facility should be monitored and
recorded at all times.
Control Valves
used to control flow in and out of storage facilities and prevent overflows.
Altitude valves operate by sensing pressure.
Pressure, psi =
2.31 x head, ft
Pump Controllers/SCADA systems
an electronic signal of the tank level to a
controller device that interacts with pumps that supply water to the tank.
Storage facilities require…
routine maintenance, including routine inspections, to ensure proper operation and
identify replacement and repair needs.
Painting
Frequency
These inspections should be
conducted every several years depending on system conditions. Flaking, peeling, and rust are signs that
repainting is needed. On average, typical storage tanks require repainting every 15 years.
Painting Process
When draining a tank for inspection or repainting, provisions should be made to ensure adequate system
operation when the tank is out of service.
Important Note: Tank painting requires a permit from the Pennsylvania Department of Environmental
Protection (PA DEP).
is a significant maintenance issue with storage facilities.
Corrosion
Factors that contribute to increased risk of corrosion inside a tank include:
Warm water,
Long detention times (minimal turnover of water in a tank), and
Corrosive water (high in dissolved oxygen and sulfate, low in pH)
Corrosion Control Methods in Tanks
Painting and routine repainting,
Coatings,
Cathodic protection, and
Addition of corrosion inhibitor as part of the water treatment process.
__________ of water quality is another significant maintenance issue with distribution storage facilities
Degradation
Three issues with storage facilities that can negatively impact water quality are
Excessive Detention Time
Contamination
Excessive Detention Time can result in
depletion of chlorine residual
Excessive detention time can result from:
Low system demands;
Improperly designed storage facilities; and
Improper system operations.
Water contamination in a storage facility can be caused by
deliberate acts such as vandalism or
terrorism, as well as by natural causes, such as animals or rain.
Ways to prevent commination in storage facilities
Restricting unauthorized access to storage facilities;
Locking and sealing access openings; and
Routine inspections and surveillance.
Drinking water storage distribution systems…
equalize demands and pressure fluctuations;
provide fire protection and emergency stores of water.
Storage facilities can be classified as
clear wells, elevated, ground level and
hydropneumatic.
Routine refill is the
normal schedule of restoring water levels to the desired amounts.
Emergency refill is
needed after excessive peak demand or emergency conditions.
Painting and corrosion control methods can
enhance the life of distribution storage
facilities.
Excessive detention time in a water storage facility can
adversely affect water quality
through depleted chlorine residual and increased chances of contamination.
The use of chlorine in drinking water began in
1908
Chlorination has remained the most common method of disinfection because
the easily detectable residual it leaves in the water
_______ and _______ may also be used to
maintain a disinfectant residual in the distribution system
Chloramines and chlorine dioxide
An adequately maintained disinfectant residual:
Protects the distribution system from microorganisms
Controls biofilm growth
Public water systems that chlorinate are required to
monitor the disinfectant residual weekly at
representative points in the distribution system
Ensuring disinfection in the distribution system is the
last
remaining barrier that prevents recontamination before the customer consumes the water and is a very
crucial component of public health protection
The minimum required distribution residual level
is 0.2 mg/L
The minimum required distribution residual level is required for…
All community water systems
All non-transient noncommunity water systems using a chlorine disinfectant
Transient noncommunity water systems with filtration of surface water or 4-log disinfection of a
groundwater source.
________ ________ ________ _______ monitoring is another way a public water system protects public health.
Routine total coliform bacteria
Coliform bacteria are
organisms that are present in the environment and in the intestines of all warm
blooded animals.
The presence of coliform bacteria in the distribution system indicates
that disease causing organisms (pathogens) could be entering the water system through a breach in the distribution
network.
The number of routine bacteriological samples required each month in the distribution system
depends
on the population served
If a total
coliform sample tests positive:
The lab will analyze the sample for E-coli, and
The public water system should collect three check samples for every coliform positive
result in accordance with their site sampling plan
If the check samples test positive for coliform, they too will be analyzed for E-coli.
An E-coli positive result indicates an acute microbial risk
If an e Coli. positive result is found…
This is a Tier 1 Violation
Notify DEP within one hour
Issue a Boil Water Advisory as soon as possible, but within 24 hours
Chlorine (Cl2) when injected into water forms the following reaction:
Cl2 + H20 —–> HOCl + HCl
Chlorine is capable of disinfecting when in the
“free residual” state.
The two free residual forms of chlorine
include:
Hypochlorous acid (HOCl), and
Hypochlorous Ion (OCL-).
Three forms of Chlorine Used
Calcium Hypochlorite
Sodium Hypochlorite
Gas Chlorine
Calcium Hypochlorite
o Produced in tablet or granular form
o Contains about 65% available chlorine
o Often used in the disinfection of mains and storage facilities.
Sodium Hypochlorite
o Yellow/greenish liquid form of chlorine
o Generally, contains about 10% or 12.5% available chlorine when purchased
o Some systems dilute with water depending on water flow and required dosage if used for
system
Gas Chlorine
o If used, only used in treatment facility
o 100% strength
o Generally shipped in 150 lb or ton cylinders
o Most dangerous of the three forms
Depletion of Chlorine Residual
Contributing Factors:
Inadequate disinfection of source,
Stagnation/excessive detention time,
Presence of ferrous ions and corrosion by-products in water, and
Presence of bio-film and organic matter in mains and storage facilities.
Depletion of Chlorine Residual Effects:
Biofilm growth, and
Inadequate protection against bacteria that cause waterborne diseases.
Disinfection Influences
pH
Temperature
Contact time
Concentration
Impurities in the water
Breakpoint Chlorination is
The chlorine dosage needed to satisfy
this initial chlorine demand of the impurities
Chlorine that is added
beyond the breakpoint chlorination dosage is….
the free residual chlorine that is used for disinfection within
the distribution system.
______ the total amount of chlorine that was added.
This includes the amount needed for the chlorine demand and the free residual chlorine.
total chlorine
____________ is determined by adding the amount of chlorine it took to reach
breakpoint chlorination and the amount of chlorine needed to hold the required residual for
disinfection.
required chlorine dosage
Chlorine dosage =
Chlorine demand + Chlorine residual.
Leaching of Coatings and Linings
Contributing Factors:
New coatings or linings,
Low pH, alkalinity, and calcium in cement and cement-lined mains and tanks, and
Stagnation/excessive detention times.
Leaching of Coatings and Linings Effects:
System contamination due to volatile organic compounds (VOCs) such as benzene, MBTE,
and other contaminants,
Increased nutrients and subsequent promotion of bacterial growth,
Increased pH, calcium, and alkalinity (from cement lining),
Taste, odor, and color issues, and
Depletion of disinfectant residual.
pH Instability
Contributing Factors:
Low buffer capacity (inadequate alkalinity), and
High alkalinity (> 1,000 mg/l) and CaCO3 (>50 mg/l).
pH Instability Effects:
Corrosion of distribution network components,
Leaching of coatings and linings,
Damage to cement and cement-lined mains and tanks, and
Scale formation.
parameters are deemed to be accreditation by rule parameters:
Turbidity
Fl-
residual disinfectant concentration
temperature
pH
Alkalinity
Orthophosphate
Silica
Calcium
Conductivity
Daily Chlorite
Mangnesium hardness
Waterborne Diseases
Contributing Factors:
Infiltration,
Inadequate disinfection,
Stagnation/excessive detention time,
Presence of nutrients, and
Presence of biofilm.
Waterborne Diseases Effects:
Gastrointestinal diseases, when digested,
Taste and odor issues, and
Interference with microbiological monitoring.
Biofilm
Contributing Factors:
Corrosion and tuberculation,
Temperature,
Stagnation/excess detention time, and
Presence of nutrients.
Biofilm Effects:
Taste and odor issues,
Release of pathogenic organisms into the distribution system, and
Interference with microbiological monitoring.
Taste, Odor, and Color
Contributing Factors:
Inadequate treatment of metals, minerals, and VOCs,
Presence of algae and microorganisms,
Leaching of coatings and linings,
High levels of disinfectant residuals,
Corrosion and tuberculation,
Infiltration, and
Formation of air bubbles.
Taste, Odor, and Color Effects:
Unpleasant appearance and taste,
Customer complaints, and
Staining can occur from precipitated iron and manganese in the distribution system.
Sediment
Contributing Factors:
Sudden changes in flow velocity (scouring),
Changes in flow direction,
Corrosion and tuberculation,
Infiltration, and
Leaching of coatings and linings.
Sediment Effects:
Reduced pipeline hydraulic capacity,
Taste, color, and odor issues,
Growth of bacteria and biofilm, and
Ineffective disinfection.
Clogging and wear of customer water meters
Water suppliers must adhere to AWWA Standard C651
when installing or
repairing water mains. This standard describes methods for adequate flushing, disinfection, and
microbiological testing.
New Mains
Contamination Prevention
When installing water mains, care should be taken to prevent contamination from dirt, debris,
animals, dirty water, or other potential contaminants. Mains should be plugged when unattended.
Also, trenches should be kept clean and dry.
New Mains Flushing
New mains should be flushed at a rate of at least 5 feet per second for approximately 30 minutes to
help remove potential contaminants. Flow is related to velocity as follows:
Flow (Q) = Velocity (V) x Area (A)
New Mains Disinfection
New mains should be disinfected prior to putting in service. Calcium hypochlorite in tablet or
granular/solution form is often used for disinfecting new mains.
New Mains Post-Disinfection
The new main should be tested for coliform after disinfection to ensure the effectiveness of the
disinfection. The main should be flushed again prior to putting it in service in order to remove the
concentrated chlorine.
The best way to make a system repair is to
do it under system pressure with the water flowing
Contamination could occur when a main is
removed from service for repairs.
AWWA Standard C651,
procedures as described above for disinfection of new mains prior to putting back in service.
New storage facilities and those removed from service for repair should also be
disinfected prior to putting
in service.
Disinfecting a storage facility could also be accomplished by
filling the tank with water that has the appropriate chlorine
residual. This can be accomplished by use of calcium hypochlorite at the tank.
Disinfection Dosage Calculation
Revised Total Coliform Rule (RTCR)
sets monitoring and compliance requirements for coliform bacteria in the distribution system.
All
systems must have a written sample siting plan with
locations that are representative of water quality
throughout the distribution system.
All systems must collect samples
monthly; the number of samples is
based on population served.
total coliform is regulated as a
Treatment Technique, where,
after a threshold of positive total coliform results, a water system needs to conduct an assessment to
identify sanitary defects and develop a plan to correct them.
Level 1 assessment triggers:
Water systems collecting <40 samples/month has 2 or more total coliform positive
(TC+) routine samples in the same month
Water systems collecting at least 40 samples per month has greater than 5.0 percent
of the routine samples in the same month that are TC+
Water system fails to take every required check samples following TC+
Level 2 assessment triggers:
Water system incurs an E. coli MCL violation
Water system triggers two Level 1 assessments within a rolling 12-month period
Treatment technique (TT) is a
requirement which specifies a specific treatment method known to
cause a reduction in the level of a contaminant which cannot practically be regulated by establishing an
MCL.
Surface Water Treatment Rule (SWTR)
requires public water systems using surface water sources to sample for disinfectant residual
levels at the same frequency, time and locations as total coliform sampling.
Disinfection By-products Rule (DBPR)
s (MCLs) for Total Trihalomethane (TTHM) and the sum of five
haloacetic acids (HAA5). The rule also establishes maximum residual disinfectant levels for chlorine,
chloramines, and chlorine dioxide.
DBPR requires systems to collect and analyze samples from the distribution system for
TTHMs and HAA5s 1/4ly, annual or triennial basis
All must be sampled per sample plan
systems must samle for disinfectant levels daily, monthly or quarterly
NOM
Natural Organic matter
refers to the
byproducts of organic matter decay such as humic acid, fulvic acid, amines, and
urea.
Factors Affecting Disinfection By-product Formation:
NOM
type and dosage of disinfectant
length of time of exposure
TTHM Formation:
Long water age:
Higher water temperatures:
High pH
HAA5 Formation:
HAA5s will increase as water age increases, but only up to a
point.
Lower pH: Opposite of TTHMs, HAA5 formation decreases with increasing pH
Disinfection Requirements Rule (DRR)
at least 0.2 mg/L
All community water systems
All non-transient noncommunity water systems using a chlorine disinfectant
Transient noncommunity water systems with filtration of surface water or 4-log
disinfection of a groundwater source.
Disinfectant residual measurements must be collected at representative locations at the same
time and location(s) as coliform samples.
Disinfectant residual measurements must also be conducted at least
once/week.
Water
systems that do not collect at least 1 coliform sample each week will need to
conduct
additional disinfectant residual measurements each week that a coliform sample is not
collected
Any location that has a disinfectant residual less than 0.2 mg/L in a month
must also be
sampled the following month.
A distribution system investigation is triggered when a single monitoring location is
<0.2 mg/L
for two consecutive months
Lead and Copper Rule
This rule requires community and nontransient noncommunity water systems to collect first draw samples
at cold water taps in homes/buildings that are at high risk of lead or copper contamination. The number of
samples sites is based on system size. Systems must conduct monitoring every six months unless they
qualify for reduced monitoring to annually or triennially. Very small systems may also qualify for lead or
copper nine-year monitoring waivers if they meet waiver criteria
Data that can be used to analyze water age may include:
Flowrate,
Velocity,
Pressure,
Tank levels,
pH,
Disinfectant residual,
Iron,
Color and taste,
DBPs, and
Heterotrophic bacteria count.
Monitoring can be used to determine if water age is
negatively affecting water quality in a
distribution system.
Inadequate turnover in storage facilities can have a
significant negative impact on water quality
within a distribution system
Monitoring at the inlets, outlets, and within storage facilities can help
identify potential water quality problems and corresponding needs for modification of system
operations to increase turnover.
Parameters to be monitored to determine potential water quality problems
Total and free chlorine residual,
pH,
Water temperature,
Turbidity,
Heterotrophic bacteria,
Total coliform bacteria,
Ammonia,
Nitrite,
Taste and odor, and
TTHMs.
Monitoring of pressure at ______ in the distribution system can be used to identify and resolve ___ or ____ pressures that may lead to contamination by backflow.
Key points, low, negative
Pressure monitoring should be conducted at
pump stations, control valves, and high elevation
points and other areas subject to low pressure
For systems that use more than one source of supply, water quality monitoring may be used to
distinguish the origin of water in a distribution system.
Monitoring of disinfectant residual, heterotrophic bacteria and nitrification can be used to determine
the effectiveness of booster chlorination in a distribution system.
Monitoring can be used to identify areas that may be negatively affected by an
emergency event,
such as a main break, repairs, or deliberate acts of terrorism.
Databases of customer
water quality complaints can be used to
help prioritize main repair and replacement, prioritize main flushing,
and determine causes of water quality problems.
Monitoring programs, which include monitoring beyond that required by regulation, may help
characterize
the distribution system and determine the cause of water quality problems.
Benefits of Flushing
reduce the need for reactive maintenance in a distribution
system by removing biofilm and other bacteriological growth, sediment, and corrosion products and helping
to prevent tuberculation.
A flushing program involves advanced planning to outline procedures,
such as the order of
hydrants to be operated and valves to be closed.
The flushing program should be
documented.
data that may be collected during hydrant flushing, which is useful for daily
system operation, includes:
Repair and replacement needs,
Water quality sample results, and
Flow and pressure readings.
There are numerous reasons for flushing water from fire hydrants.
Testing the fire hydrants to ensure they are working properly.
System flushing to expel the sediment or minerals that settles to the bottom of our water
mains and help in maintaining a clean and aesthetically pleasing water supply to customers.
Respond to customer complaints (one way to treat taste and odor issues).
Increase chlorine residual in area of system.
Expel air from new or recently repaired water lines.
Types of flushing strategies include:
-Spot
-Routine Flushing in stagnant areas
-Scheduled system-wide flushing
Spot Flushing
(reactive) may be used when there are localized water quality complaints and
in the case of emergencies.
Routine flushing in stagnant area
(short term preventative)
used in problematic areas with
dead ends or low demand areas to fix long detention times which can degrade water quality
A fully looped system may eliminate the need for…
stagnant flushing
Scheduled system-wide flushing
(long term preventative):
this is the most comprehensive
type of flushing program which helps maintain water quality and the useful life of the mains.
Scheduled system-wide flushing is typically conducted…
bi-annually in the spring and fall.
Flushing methods include…
-Directional flushing
-Conventional/traditional flushing
-Continuous blow off
Directional flushing
is the recommended method of annual or semi-annual flushing to
maintain water quality in the distribution system.
Requires the operator to isolate sections of water mains to allow for flushing that
particular main from beginning (nearest the water plant/fresh water) to the end
(furthest point).
Directional flushing
Conventional/traditional flushing
is typically used in response to water quality complaints.
Water moves in all direction in conventional flushing, may have low flow velocities which do
not allow for system scouring.
Continuous blow off
is used to bled water from stagnant areas in a system. This type of
flushing uses large quantities of water at flow velocities less than 1 foot per second. This
type of flushing does not clean the system.
To properly clean the distribution system, it is important to keep flushing flow velocities
between 5
feet per second to 12 feet per second (lower velocities for discolored water and higher velocities for
sediment removal).
Fire hydrant flushing steps:
- Notify customers in particular
- Isolate section to be flushed from the rest of the system:
- Open hydrant/blow off valves slowly until the desired flow is obtained.
- Maintain 20 psi minimum flushing pressure.
- Record data (not including hydrant data).
- When water clears, close hydrant/blow off valve slowly
- Reopen valves connecting flushed section to the larger system.
- Proceed to next section to be flushed.
When flushing, notify these customers in particular…
-Hospitals
Dialysis clinics
Food processing
Bottling
Specialized manufacturing
When flushing system be aware of water…
Direct water away from traffic, pedestrians, underground utility vaults and private lands.
Confirm storm drains or natural water courses can handle the flow
Prevent contaminated water from discharging into sensitive areas
Dechlorination may be necessary
Flushing water into a tank truck may be required
When flushing what should you record…
Hydrant No
# of turns
Static PSI
Residual PSI
Flow PSI
Time (stat/stop0
Water Quality
Remarks/Maintenance
What is a cross-connection…
is any point in a water distribution system where chemical, biological, or radiological
contaminants may come into contact with potable water
A ______ ________ ________ installed at every
point of cross connection prevents contaminated water from entering the potable water distribution system.
backflow prevention device
5 key elements of an effective cross-connection control program
Establish proper authority to initiate and enforce plan.
Utilize approved backflow prevention devices, test and maintain as needed.
Use only certified personnel to test devices and inspect sites.
Maintain accurate installation, testing, and inspection records.
Educate the public about the danger of cross-connection.
3 things that cleaning and lining of mains can be conducted to…
Improve pipeline hydraulic capacity,
Resolve water quality problems, and
Prevent future water quality problems.
2 methods of cleaning lines…
Flushing
Mechanical Cleaning methods
5 kinds of mechanical cleaning methods
Pigs
Swabs
Scrapers or brushes
Induction of Air
Ice Pigging
Lining may be desirable when…
the existing main is structurally sound and of sufficient diameter.
Linings do not improve the structural integrity of the existing pipeline
lining invovles applying a ______ ______ _____ or an _____ to an existing pipe in order to improve flow and prevent corrosion.
cement mortar lining
epoxy
________ in pipelines is a primary cause of deteriorating water quality within a distribution system due to
water age.
Stagnation
Stagnation contributes to depletion of…
disinfectant residual, bacteriological issues, turbidity,
color, taste, and odor problems.
Frequently, there is a build-up of _______ and ____________ sediment in dead end sections.
iron and Manganese
Potential Causes of Stagnation
Dead-end or non-looped mains
Oversized Mains
Extremely long stretches
minimal customer demands
Distribution system water quality issues include 3 things
chemical
biological
aesthetic
_______ ________ is a common method used to make sure that subscribers at the far ends of the
distribution system are protected from biological pathogens in the drinking water.
Chlorine residual
The ______ _________ ____ is a regulation that requires all public water systems to sample for total
coliform bacteria. Depending on sample results, t
Total Coliform Rule
Water systems must also meet the distribution water quality standards prescribed in what regulation/plan?
Disinfection Byproducts Rule (DBPR)
Disinfection Requirements Rule (DRR)
Examples of aspects of water in the distribution system that can be monitored to help assure that the quality of water is being maintained.
Flowrate
disinfection residual
color
taste
