CE 3372 Water Systems DesignLecture 006: Introduction to US EPA-NET

EPANET Introduction/Workshop Example problems

Network Design Principles Introduction to Project

Outline

Install Example 1 – Flow between two reservoirs Example 2 – Three reservoir (branched) Example 3 – Two reservoir, 4 pipes (loop) Example 4 – Lifting with a pump

Workshop

Sketch a layout on paper Identify pipe diameters; length; roughness

values Identify node elevations; demands Supply reservoir (or tank); identify reservoir

pool elevation Identify pumps; pump curve in problem units

Model Preparation

Example 2 – Flow between two reservoirsExample 1

Example 2 – Three reservoir (branched)Example 2

Example 3 – Two reservoir, 4 pipes (loop)Example 3

Example 4 – Lifting with a pumpExample 4

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

Network Design Principles

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

DESIGN

Pressure

Velocity

Age

Chlorine concentration

Fire Flow

DESIGN REQUIREMENTS

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 Offices (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.

Q = required fire flow in gpmC = coefficient related to the type of constructionA = total floor 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, offices, 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

Semester design project is to conceptual design a water distribution system and a storm water sewer system for a small residential development Hydraulic analysis for both systems to

demonstrate that the systems will supply/convey as sufficient capacity

Project

Demand estimation is used to determine how much water a system is likely to use (for sizing reservoirs and tanks

Flow rate estimation (a plumber’s perspective) is used to determine how much capacity a system should be able to provide

Estimating Flow Rate

How Much Water Can You Actually Get? Flow Rates are measured in gallons per minute (gpm). For our purposes, we will talk about the amount of

water that you can get through a pipe at a velocity of 8 feet per second (a standard velocity used to engineer a plumbing system).

Plumbing diameter will limit the flow rate you can get – the larger the pipe, the more water you can get. A home with 1″ plumbing can use substantially more water than a home with 3/4″ plumbing.

How Much Water ?

Meter to house

Inside home

1. Think about the maximum number of fixtures and appliances you might operate at the same time.

2. Look at the chart to see how many gallons per minute each device requires.

3. Add up the flow rates for all the devices you selected.

You just figured out the PEAK FLOW RATE that you need.

Now, think about your continual water use, or water use that may run for more than 10 minutes. Add up the fixtures again, and you just calculated your SERVICE FLOW RATE.

How Much Needed? (1)

http://extension.psu.edu/natural-resources/water/drinking-water/best-practices/water-system-planning-estimating-water-use

How Much Needed? (2)

Estimate need per connection to size the system; Run a hydraulic model at these values to size

pipes Estimate demand to evaluate how the

system is likely to perform in terms of pressure zones and such Run a hydraulic model at these values to check

pressures – no fire flow Run a hydraulic model with fire flow to check

minimum pressures

Using the estimate

Several readings on server will be useful:

Readings

Pumps Review how to size How to simulate in EPANET NPSH considerations

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