Water Distribution Systems, Network Systems

CE 3372 WATER SYSTEMS DESIGN

OUTLINE

Review of Lecture 3Water Distribution Systems

Network Systems

Define HydraulicsWhat is the Energy EquationName some assumptions of the Energy EquationDifference in EGL and HGL2 Main types of Head Loss3 types of head loss models

REVIEW

Water Supply System Includes water supply Treatment Facilities Pumping facilities Transmission lines Local distribution network

WATER DISTRIBUTION

Distribution network - Consists of items designed to convey potable water at adequate pressures and discharges Pipes Fittings Valves Other appurtenances

WATER SUPPLY SYSTEM

Who? Personnel within the water company Engineers / Consultants

Design Requirements? Pressure Fire Flow Potable water Cost Effi cient $$

Design parameters and regulations? State board of health Local city/county health departments EPA, AWWA, ANSI

DESIGN

Pressures Must be high enough to..

overcome head losses in the system. But not too high to...

prevent damage to fittings and other appurtenances.

Pressure Zones – Set pressurized areas (min and max) within the system by storage, boosters, or pressure control valves. Can also be due to varying pipe size and topography May be generated to ensure reliability in meeting fluctuation

demands.

System pressures are adapted to requirements. Hilly areas – booster pumping Minimum pressures vary state to state Established by the state’s Health Department / other agency Fire Marshall may establish additional requirements.

PRESSURE

Fire Flow Parameters Each municipality establishes own parameters based on

local cond. Insurance Services Offi ces (ISO) - Most used

“Guide for Determination of Required Fire Flow” Recommends criteria for

Establishing insurance rates Classifying mun. with reference to their fire defenses and physical cond.

F = required fi re fl ow in gpmC = coeffi cient related to the type of constructionA = total fl oor area in ft2 (excludes basements)

FIRE FLOW

Hydraulic Characteristics Pressures and discharges are a functions of HC Length Size Condition of pipe

Service Characteristics Demand as it relates to:

Present and projected population Economic base Fire flow Climate

WATER SUPPLY SYSTEM

Water utility company …who is responsible for the water quality and operation of

the distribution system.

Companies exist in two forms public entity that

..“exists for the health, safety, and welfare of the public” privately owned utility that ..provides water for profit

WATER UTILITY

WATER SUPPLY SYSTEM

Gravity Dependable Source of supply must be located well above the city High-pressure demand for fire-fighting may require pumper

trucks

Pump Least Desirable Pressures vary substantially with variations in flow Provides no reserve if power failure

Pump with Storage Most common Water supplied at approximately uniform rate Flow in excess of consumption stored in elevated tanks

PIPE SYSTEM

Primary Mains (Arterial Mains) Form basic structure of the system Carry flow from pumping station to elevated storage tanks Carry flow from elevated storage tanks to service areas

Laid out in interlocking loops Mains not more than 1 km (3000 ft) apart

Valved at intervals of not more than 1.5 km (1 mile) Smaller lines connecting to them are valved

PIPE SYSTEM

Secondary Lines Form smaller loops within the primary main system Run from one primary line to another

Spacings of 2 to 4 blocks Provide large amounts of water for fire fighting with out

excessive pressure loss

PIPE SYSTEM

Small distribution lines Form a grid over the entire service area Supply water to every user and fire hydrants –Connected to

primary, secondary, or other small mains at both ends Valved so the system can be shut down for repairs Size may be dictated by fire flow except in residential areas with

very large lots

Water source (Main Supply)• Lake• River• Aquifer

Treatment Facility• Treats and disinfects water• Meet water quality standards• Potable water

Transmission Lines• Convey water from

source – treatment facility facility – network

Pumping Facilities• Provide energy to move water

Intermediate Storage Facilities• Stabilize line pressures• Reserve for peak demand periods

• Provide storage for fire flow req.

Distribution Lines• Convey water from

storage – service areas

• Looped(grid) and Branched Layouts

Appurtenances• Fire Hydrants. Valves, auxiliary pumps, fittings

WATER SUPPLY SYSTEM

WATER USE SYSTEMS

Spatial and temporal distribution in support of human habitation Water supply/treatment/distribution Waste water collection/treatment/discharge

Capacity is based on POPULATION served hydraulic dominated designs

WATER USE AND DEMAND

Water Use Consumptive

Municipal Agricultural Industrial Mining

Non-consumptive Hydropower Transportation Recreation

Water Demand Quantity that consumers use per unit of time Ex: Mgpd Depends on population, climate, industry and economic

factors

WATER DEMAND

Residential Single-family, multi-family (apartments) Water for drinking, landscape, swimming, fires,

street cleaning, etc. Usually two demand peaks (morning and evening)

Commercial Motels, hotels, offi ces, shopping centers Usually less peak demand and less varied than

residential

Industrial Chemical plants, food processing plants, mines Water for fabrication, cooling, petroleum refining,

etc. Water use depends on type of industr.

ASSIGNING DEMAND

Assign demand using network models (links and nodes)

Network models contain nodes that represent a multitude of actual connections .

While conceptually possible to model to every single connection,it is discouraged because Model is hard to maintain Small errors may go unnoticed The operation of any single connection is not well known.

NETWORK TYPES

Branch No circulation Has terminals and dead-ends

Water in dead-ends is stagnant Disinfection residual Corrosion

NETWORK TYPES

Grid/Loop Furnishes supply from more than one direction

Water circulates Disinfection is more effective. Water “age” in system is younger (fresher).

In case of water main break, fewer people are inconvenienced

NETWORK TYPES

Loop vs. Branch during network failure Every link in a branch system is a single point of failure

that isolates all downstream nodes. Not with loop, only main supply line is failed

Distribution networks are multi-path pipelines

Node Inflow =

Outflow Energy is

unique valueLinks

Head loss occurs along line path

BRANCHED SYSTEM

BRANCHED SYSTEM

Continuity at the node

BRANCHED SYSTEM

Head loss in each pipe

Common head at the node

4 Equations, 4 unknownsNon-linear – solve by

Newton-Raphson/Quasi-Linearization

Quadratic unknown – can find solution in iterations

BRANCHED SYSTEM

TWO RESERVOIR EXAMPLE – Refer to spreadsheet

BRANCHED SYSTEM

Looped system is an extension of branching where one or more pipes rejoin at a diff erent node.

LOOPED SYSTEM

Nodes: Inflow = Outflow Energy Unique

Links Head loss along pipe Head loss in any loop is zero

LOOPED SYSTEM

LOOP