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Water supply

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This document provides an overview of municipal water supply systems, including sources of water, water treatment processes, storage, distribution, and calculations for pressure. It describes how water is obtained from both groundwater aquifers and surface sources like rivers and reservoirs. Water is treated depending on source quality before being pumped to storage tanks and distributed through a piping network to customers, with minimum pressures of 40 psi for residences. The document also defines key terms and shows examples of calculating static head, pressure, head loss, and actual delivery pressure.

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WATER SUPPLY
TABLE OF CONTENTS • Why Treat Water? • Uses of Water • Water Supply System • Sources of Water • Water Treatment • Water Storage • Distribution System • Definitions • Calculating Water Supply Pressure
Why Treat Water? • Society realized long ago that human health and the welfare of the general population are improved if public water supplies are treated prior to use. • Nearly all structures require a water supply. • Appropriate flow rate, pressure, and water quality are necessary for effective use.
Uses of Water • Bathing • Toilets • Cleaning • Food preparation • Cooling • Fire protection • Industrial purposes • Drinking water = Potable water ©iStockphoto.com
Water Supply System
Sources of Water Aquifers (Groundwater) • Primary source of drinking water • Porous consolidated rock or unconsolidated soil • Groundwater fills spaces • Wells and pumps used to remove water Aquifer Courtesy USGS at http://pubs.usgs.gov/circ/circ1139/htdocs/boxa.htm This image was reproduced from groundwater.org with the permission of The Groundwater Foundation. © 2010 The Groundwater Foundation. All Rights Reserved
Sources of Water Surface Water • Lakes, reservoirs, rivers • Rivers dammed to create reservoirs • Reservoirs store water during heavy rain/snow Courtesy NASA http://www.ghcc.msfc.nasa.gov/surface_hydrology/water_ma nagement.html Courtesy USDA http://www.ks.nrcs.usda.gov/news/highlights/2006_april.html ©iStockphoto.com Lake Tuscaloosa Dam
Water Treatment • Amount of treatment depends on quality of the source • Ground water requires less treatment than surface water Courtesty USGS http://pubs.usgs.gov/fs/2004/3069/ The city of Salem water treatment facility withdraws water from the North Santiam River.
Water Storage Pumped to Storage Tank • Storage • Water pressure opsi o1 psi = 2.31 feet of water NOAA http://www.csc.noaa.gov/alternatives/infrastructure.html
Water Distribution System • Consists of water lines, fittings, valves, service lines, meters, and fire hydrants • Loop system more desirable than branch system – Isolation valves – Water flows in more than one direction LOOP SYSTEM BRANCH SYSTEM
Water Distribution System • Typical new system pipe – Thermoplastic or ductile iron – Reinforced concrete in larger mains • Older system pipe – Cast-iron or asbestos cement • Typical distribution pressure of 65 – 75 psi • Designed for less than 150 psi wikimedia
Consumer • Residential, commercial, and industrial facilities • Residential – Min. distribution pressure = 40 psi – Max. distribution pressure = 80 psi • Pressure-reducing valve • Commercial or industrial facilities – May require higher pressure – Pumps can increase pressure ©iStockphoto.com ©iStockphoto.com
Definition Head Relates energy in an incompressible fluid (like water) to the height of an equivalent column of that fluid
Definition Static Head • Potential energy of the water at rest • Measured in feet of water • Change in elevation between source and discharge • Ex: What is the static head at a residential supply line if the water level in the elevated tank is 943 ft and the elevation at the supply line is 890 ft? 943 ft – 890 ft = 53 feet of water EPA at http://www.epa.gov/region02/superfund/npl/mohonkr oad/images.html
Definition Static Pressure • Pressure of water at rest • Measured in pounds per square inch (psi) • 2.31 feet of water = 1 psi • Ex: What is the static pressure at distribution if the static head is 53 ft of water? psi 1 ft psi   53 22.9 ft 2.31 • Is this the pressure at which water would exit a faucet in the house?
Water Pressure Calculations • How far above the supply line must the water level in a water tower be in order to provide a minimum 40 psi? 40 psi 2.31 ft = 92.3 ft of water • Except water loses pressure as it travels through pipe. NOAA http://www.csc.noaa.gov/alternatives/in frastructure.html
Definitions Head Loss • Energy loss due to friction as water moves through the distribution system − Pipes − Fittings • Elbows, tees, reducers, etc. − Equipment (pumps, etc.) • Major losses = head loss associated with friction per length of pipe • Minor losses = head loss associated with bends, fittings, valves, etc.
Calculating Head Loss Hazen-Williams formula 1.85 10.44    h  f L Q 1.85 4.8655 C d Where: hf = head loss due to friction (ft) L = length of pipe (ft) Q = flow rate of water (gpm) C = Hazen-Williams constant d = diameter of the pipe (in.)
Hazen-Williams Constant, C
Calculating Head Loss Minor Losses • Hazen-Williams formula used for straight pipe • Need equivalent length for each fitting to account for minor losses. • Accepted equivalent length values published ©iStockphoto.com
Equivalent Length in feet of pipe (Generic)
Calculating Total Equivalent Length Example A 10 inch flanged cast iron water supply line provides service to a home. The pipe between the water tower and the meter includes seven regular 90 degree elbows, three line flow tees, eleven branch flow tees, and six gate valves between the water tower and a service connection to a residence. What is the equivalent length of the fittings and valves? Fitting Quantity Equivalent Length (ft) Total Equiv. Length (ft) Reg. 90 deg elbow 7 14.0 98.0 Line flow tee 3 5.2 15.6 Branch flow tee 11 30.0 330.0 Gate valve 6 3.2 19.2 Total 462.8
Calculating Head Loss Example What is the head loss in the 10 inch cast iron supply line with a flow rate of 110 gpm if the pipe is 3.2 miles long and includes the fittings from the previous slide? ft  mile Pipe Length = (3.2 miles)(5280 ) 16896 ft Total Equiv. Length = Pipe Length + Equiv. Length of Fittings Total Equiv. Length = 16896 ft + 462.8 ft = 17358.8 ft
Calculating Head Loss Hazen-Williams Formula 1.85 10.44   1.85 4.8655 f L Q h C d   10.44 (17358.8 ft)(110 gpm)  h  f (100) (1 0 in) 1.85 1.85 4.8655 = 2.94 ft
Definition Dynamic Head • Head of a moving fluid • Measured in feet of water Courtesy Constructionphotographs.com Dynamic Head = Static Head – Head Loss
Definition Dynamic / Actual Pressure • Measured in psi Dynamic Pressure = Actual Pressure Actual Pressure = Dynamic Head  psi ft 1 2.31
Water Pressure Calculations Example The water level in the water tower supplying the home in the previous example is 1487 ft. The elevation of the supply line at the residence is 1246 ft. Find the static head, the static pressure, the dynamic head, and the actual pressure of the water as it enters the residence.
Example Static Head= 1487 ft – 1246 ft  241 ft Static Pressure = 1 psi 241 ft 104.3 psi Head Loss (major and minor) = 2.94 ft Dynamic Head = Static Head – Head Loss  241 ft – 2.9 ft  238.1 ft Dynamic Pressure =   2.31 ft 1 psi 238.1 ft 103.1 psi   2.31 ft
References Dion, T. (2002). Land development for civil engineers (2nd Ed.). New York: John Wiley & Sons. Lindeburg, M. (2008). Civil engineering reference manual for the PE exam (11th Ed.). Belmont, CA: Professional Publications, Inc.
Image Sources USDA at http://www.ks.nrcs.usda.gov/news/highlights/2006_april.html NASA at http://www.ghcc.msfc.nasa.gov/surface_hydrology/water_mana gement.html NOAA at http://www.csc.noaa.gov/alternatives/infrastructure.html www.istock.com The Groundwater Foundation at www.groundwater.org USGS at http://pubs.usgs.gov/fs/2004/3069/ EPA at http://www.epa.gov/region02/superfund/npl/mohonkroad/im ages.html Wikimedia at http://en.wikipedia.org/wiki/File:Largediapvc.jpg www.constructionphotographs.com

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Water supply

  • 2. TABLE OF CONTENTS • Why Treat Water? • Uses of Water • Water Supply System • Sources of Water • Water Treatment • Water Storage • Distribution System • Definitions • Calculating Water Supply Pressure
  • 3. Why Treat Water? • Society realized long ago that human health and the welfare of the general population are improved if public water supplies are treated prior to use. • Nearly all structures require a water supply. • Appropriate flow rate, pressure, and water quality are necessary for effective use.
  • 4. Uses of Water • Bathing • Toilets • Cleaning • Food preparation • Cooling • Fire protection • Industrial purposes • Drinking water = Potable water ©iStockphoto.com
  • 6. Sources of Water Aquifers (Groundwater) • Primary source of drinking water • Porous consolidated rock or unconsolidated soil • Groundwater fills spaces • Wells and pumps used to remove water Aquifer Courtesy USGS at http://pubs.usgs.gov/circ/circ1139/htdocs/boxa.htm This image was reproduced from groundwater.org with the permission of The Groundwater Foundation. © 2010 The Groundwater Foundation. All Rights Reserved
  • 7. Sources of Water Surface Water • Lakes, reservoirs, rivers • Rivers dammed to create reservoirs • Reservoirs store water during heavy rain/snow Courtesy NASA http://www.ghcc.msfc.nasa.gov/surface_hydrology/water_ma nagement.html Courtesy USDA http://www.ks.nrcs.usda.gov/news/highlights/2006_april.html ©iStockphoto.com Lake Tuscaloosa Dam
  • 8. Water Treatment • Amount of treatment depends on quality of the source • Ground water requires less treatment than surface water Courtesty USGS http://pubs.usgs.gov/fs/2004/3069/ The city of Salem water treatment facility withdraws water from the North Santiam River.
  • 9. Water Storage Pumped to Storage Tank • Storage • Water pressure opsi o1 psi = 2.31 feet of water NOAA http://www.csc.noaa.gov/alternatives/infrastructure.html
  • 10. Water Distribution System • Consists of water lines, fittings, valves, service lines, meters, and fire hydrants • Loop system more desirable than branch system – Isolation valves – Water flows in more than one direction LOOP SYSTEM BRANCH SYSTEM
  • 11. Water Distribution System • Typical new system pipe – Thermoplastic or ductile iron – Reinforced concrete in larger mains • Older system pipe – Cast-iron or asbestos cement • Typical distribution pressure of 65 – 75 psi • Designed for less than 150 psi wikimedia
  • 12. Consumer • Residential, commercial, and industrial facilities • Residential – Min. distribution pressure = 40 psi – Max. distribution pressure = 80 psi • Pressure-reducing valve • Commercial or industrial facilities – May require higher pressure – Pumps can increase pressure ©iStockphoto.com ©iStockphoto.com
  • 13. Definition Head Relates energy in an incompressible fluid (like water) to the height of an equivalent column of that fluid
  • 14. Definition Static Head • Potential energy of the water at rest • Measured in feet of water • Change in elevation between source and discharge • Ex: What is the static head at a residential supply line if the water level in the elevated tank is 943 ft and the elevation at the supply line is 890 ft? 943 ft – 890 ft = 53 feet of water EPA at http://www.epa.gov/region02/superfund/npl/mohonkr oad/images.html
  • 15. Definition Static Pressure • Pressure of water at rest • Measured in pounds per square inch (psi) • 2.31 feet of water = 1 psi • Ex: What is the static pressure at distribution if the static head is 53 ft of water? psi 1 ft psi   53 22.9 ft 2.31 • Is this the pressure at which water would exit a faucet in the house?
  • 16. Water Pressure Calculations • How far above the supply line must the water level in a water tower be in order to provide a minimum 40 psi? 40 psi 2.31 ft = 92.3 ft of water • Except water loses pressure as it travels through pipe. NOAA http://www.csc.noaa.gov/alternatives/in frastructure.html
  • 17. Definitions Head Loss • Energy loss due to friction as water moves through the distribution system − Pipes − Fittings • Elbows, tees, reducers, etc. − Equipment (pumps, etc.) • Major losses = head loss associated with friction per length of pipe • Minor losses = head loss associated with bends, fittings, valves, etc.
  • 18. Calculating Head Loss Hazen-Williams formula 1.85 10.44    h  f L Q 1.85 4.8655 C d Where: hf = head loss due to friction (ft) L = length of pipe (ft) Q = flow rate of water (gpm) C = Hazen-Williams constant d = diameter of the pipe (in.)
  • 20. Calculating Head Loss Minor Losses • Hazen-Williams formula used for straight pipe • Need equivalent length for each fitting to account for minor losses. • Accepted equivalent length values published ©iStockphoto.com
  • 21. Equivalent Length in feet of pipe (Generic)
  • 22. Calculating Total Equivalent Length Example A 10 inch flanged cast iron water supply line provides service to a home. The pipe between the water tower and the meter includes seven regular 90 degree elbows, three line flow tees, eleven branch flow tees, and six gate valves between the water tower and a service connection to a residence. What is the equivalent length of the fittings and valves? Fitting Quantity Equivalent Length (ft) Total Equiv. Length (ft) Reg. 90 deg elbow 7 14.0 98.0 Line flow tee 3 5.2 15.6 Branch flow tee 11 30.0 330.0 Gate valve 6 3.2 19.2 Total 462.8
  • 23. Calculating Head Loss Example What is the head loss in the 10 inch cast iron supply line with a flow rate of 110 gpm if the pipe is 3.2 miles long and includes the fittings from the previous slide? ft  mile Pipe Length = (3.2 miles)(5280 ) 16896 ft Total Equiv. Length = Pipe Length + Equiv. Length of Fittings Total Equiv. Length = 16896 ft + 462.8 ft = 17358.8 ft
  • 24. Calculating Head Loss Hazen-Williams Formula 1.85 10.44   1.85 4.8655 f L Q h C d   10.44 (17358.8 ft)(110 gpm)  h  f (100) (1 0 in) 1.85 1.85 4.8655 = 2.94 ft
  • 25. Definition Dynamic Head • Head of a moving fluid • Measured in feet of water Courtesy Constructionphotographs.com Dynamic Head = Static Head – Head Loss
  • 26. Definition Dynamic / Actual Pressure • Measured in psi Dynamic Pressure = Actual Pressure Actual Pressure = Dynamic Head  psi ft 1 2.31
  • 27. Water Pressure Calculations Example The water level in the water tower supplying the home in the previous example is 1487 ft. The elevation of the supply line at the residence is 1246 ft. Find the static head, the static pressure, the dynamic head, and the actual pressure of the water as it enters the residence.
  • 28. Example Static Head= 1487 ft – 1246 ft  241 ft Static Pressure = 1 psi 241 ft 104.3 psi Head Loss (major and minor) = 2.94 ft Dynamic Head = Static Head – Head Loss  241 ft – 2.9 ft  238.1 ft Dynamic Pressure =   2.31 ft 1 psi 238.1 ft 103.1 psi   2.31 ft
  • 29. References Dion, T. (2002). Land development for civil engineers (2nd Ed.). New York: John Wiley & Sons. Lindeburg, M. (2008). Civil engineering reference manual for the PE exam (11th Ed.). Belmont, CA: Professional Publications, Inc.
  • 30. Image Sources USDA at http://www.ks.nrcs.usda.gov/news/highlights/2006_april.html NASA at http://www.ghcc.msfc.nasa.gov/surface_hydrology/water_mana gement.html NOAA at http://www.csc.noaa.gov/alternatives/infrastructure.html www.istock.com The Groundwater Foundation at www.groundwater.org USGS at http://pubs.usgs.gov/fs/2004/3069/ EPA at http://www.epa.gov/region02/superfund/npl/mohonkroad/im ages.html Wikimedia at http://en.wikipedia.org/wiki/File:Largediapvc.jpg www.constructionphotographs.com