WATER

DISTRIBUTION
SYSTEMS
Reservoirs and reservoir locations . Types of
distribution systems . Distribution network layout .
Design requirements . Valves and appurtenances.
(Chapter 7)

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

SETTING THE SCENE

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

The water supply network should:

■ Supply sufficient quantity of

water to satisfy demands of
users:
– Domestic use
– Industrial use
– Commercial use
– Agricultural use
– Fire demand
■ Provide adequate quality of water
to the users

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Consideration for designing a water
supply network:
■ Components of water systems (networks, dams, reservoirs, etc.) should be sufficient
for the needs of a community or catchment area.
■ Factors for determining these flows are:
Read about
– Design period: for how long is your water system expected to function. it on page
– Design population: population growth 16
– Design flows: rates of water and wastewater flows
– Design area: the catchment area
– Design hydrology: Rainfall and runoff quantities

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Typical Water Supply System (1)

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Typical Water Supply System (2)

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

 STORAGE
COMPONENTS
Page 137

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Types of Service Storage

■ Three types of service storage in water supply systems:

– Equalizing (or operating) storage
■ To ‘equalize’ pumping rates in the short term.
■ To equalize supply and demand on the long term
– Fire reserve
■ To provide water in the event of a fire.
– Emergency reserve
■ To provide water during emergencies

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Determine Equalizing Storage Volume

Mass Diagram
Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018
■ lets solve the following example on Excel. Then you can solve 7.2 – 7.4.

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Fire and Emergency Reserve

Example of how to account for

fire and emergency storage.
Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018
Location of Reservoirs in the Design
Area

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Pictures of Water Storage

Standpipe

Elevated water
storage,
Duraz, Bahrain

Water tank, Surface water

Khobar, Saudi storage dam
Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018
 WATER SUPPLY
NETWORK

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Types of Water Supply Networks (1)

■ They can be:

– Gravity Supply
– Pumped Supply
– Both

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

 Types of Water Supply Networks (2)

■ There are
various layouts
for a network
but two basic
types are:
– Branching
pattern
– Gridiron
System

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Types of Water Supply Networks (3)

Branching Gridiron
Pattern Pattern
■ Dead Ends ____ ____
■ Ease of maintenance ____ ____
■ Economical ____ ____
■ Less cut-off valves ____ ____
■ Simple to design ____ ____
■ Pressure distribution ____ ____
■ Reliable water supply ____ ____

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Design Requirements
According to specifications in page 141-142

■ Velocity of flow should not exceed 1m/s (can reach 2m/s in special circumstances)
■ Pressure throughout the system is usually within the following limits
– For residential areas: 150 – 300 kpa
– For commercial areas: 400 – 500 kPa
– In the event of fire, pressures should not drop to less than 150 kPa

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Designing a Water Supply Network
Page 142

■ The Hardy-Cross Method is used for simple

systems
– Continuity Equation has to be satisfied
– Hazen-Williams Eq for head loss is used

– Clockwise head loss is positive

– Anti-clockwise head loss is negative
– ∑HL = 0 for a loop
– Inflow to node (+ve) = outflow from node (-ve)
– We might know flows (Q) through pipes or
heads (H) at nodes.

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Derivation
of Hardy -
Cross
Method –
Balancing
Heads and
Flows

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Designing a Simple
Network
■ Procedure for designing a water
supply network is on page 144-145
■ Let’s solve Example 7.1
■ Then you can solve Problems 7-1
and 7-5

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Pipe Equivalence

■ A complex system of pipes is reduced to a single hydraulically equivalent line.

■ Cannot be applied directly to pipe systems containing crossovers or takeoffs
■ Generally, pipes contribute little to no-flow when:
– They are at right angles to the general direction of flow
– When the pipe diameter is <150mm in small systems
– When the pipe diameter is <200mm in large systems

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Pipe Equivalence

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Computer Modelling of a Water Supply
Network Using PCSWMM (with integrated
EPANET2)

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

APPURTENANCES AND
MISCELLANEOUS

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Valves, Gates, Joints, etc (1)

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Valves, Gates, Joints, etc (2)

■ Gate valves
Read pages 122-124
■ Check valves *And watch video on Blackboard: Pipeline Appurtenances
■ Air-vacuum and air relief valves
■ Pressure-regulating valves
■ Backflow preventers

■ Main points to pay attention to:

– What is the main purpose of each valve?
– When and where are these valves installed?

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Water Hammer

■ Watch educational video on Blackboard: What is water hammer?

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Multiple Lines

■ Needed when pipe size required

exceeds manufacturer’s maximum
available size
■ When possible failure could put the
line out of commission for a long
time
■ Multiple lines usually cost 30%-50%
more than an equivalent single pipe
■ Parallel lines can be connected with
gates and valves at intervals to help
direct flow during maintenance
periods

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Cross-Sections

■ Circular cross-sections are always preferred

– Largest hydraulic radius for a given volume of water (hence hydraulic capacity)
– least surface (frictional) resistance to for a given volume of water
■ There are various other cross-section available

Hydraulic radius = cross-sectional area of flow/wetted perimeter

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Pipes’ Structural Requirements

■ Internal pressure equal to the full head of

water
■ Unbalanced pressures at bends, contractions,
and closures
■ Water hammer or increased internal pressure
due to rapid change in velocity or
opening/closing of gates/valves
■ External loads from backfill or traffic
■ Their own weight of piers or hangers
■ Temperature-induced expansion of contraction

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

REAL-LIFE SCENARIO

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Wadi Al-Sail Example

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Typical Procedure for Design

■ You either get the plans from the architects or transport engineers, or, you conduct a
survey to determine the topography
■ Determine the location of the rising main or the nearest water storage
■ Mark tentative layout of the pipelines and appurtenances
■ Estimate demand (domestic, commercial, agricultural …) based on the population,
types of industries, etc. and according to the local standards
■ Analyse the network (usually performed with software) and check that:
– Pressures are within acceptable limits
– Velocity constraints are satisfied
■ Repeat the design to determine the most economical design.
■ Optimization may be required, however, this is usually done with software.

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

 WATER SUPPLY
TREATMENT

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Unwanted Substances
Chapter 8 (158-163)

■ Living organisms
■ Organic contaminants: chlorinated hydrocarbons (pesticides), volatile organic
chemicals (VOC) from industries
■ Inorganic contaminants
– Suspended solids
– Dissolved materials: aluminium, arsenic, fluoride, lead, …
■ There are EPA standards for minimum concentrations/quantities of different
substances in water for its safe use.

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018

Typical Water Treatment Processes

■ Watch video on Blackboard (Drinking Water Treatment) about water treatment

processes. Focus on:
– Coagulation: add coagulant to coagulate organic material
– Flocculation: helps coagulated material to form large clumps
– Dissolved air flotation: Remove the clumps with dissolve air:
– Filtration: filters remove remaining material in the water.
– Disinfection: with ozonation, chlorination, Ultra Violet Light.
■ Desalination (watch video: Seawater Desalination). Focus on:
– How reverse osmosis works
– Steps of desalination: filtration, reverse osmosis, energy recovery, brine outfall,
final potable water treatment (CaCO3) and disinfection.

Dr Abrar Habib | University of Bahrain | Civil Engineering Department | 2018