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CHAPTER 14 Water Supply Systems
Knowledge Objectives • Describe how municipal water systems supply water to communities. • Describe the common guidelines that govern the location of fire hydrants. • List the types of fire hydrants. • Describe the characteristics of dry-barrel hydrants. • Describe the characteristics of wet-barrel hydrants.
Knowledge Objectives • • • Explain the principles of fire hydraulics. Describe how water flow is measured. Describe how water pressure is measured. Compare potential and kinetic energy. Describe the similarities between static pressure and normal operating pressure of a system.
Knowledge Objectives • Explain how friction loss affects water pressure. • Explain how elevation pressure affects water pressure. • Describe how to prevent water hammer. • Describe how to inspect a fire hydrant. • Describe how to test a fire hydrant.
Knowledge Objectives • Describe the equipment and procedures that are used to access static sources of water. • Describe the characteristics of a mobile water supply apparatus. • Describe the advantages of a portable tank system.
Skills Objectives • • Operate a dry-barrel fire hydrant. Shut down a dry-barrel fire hydrant. Operate a wet-barrel fire hydrant. Shut down a wet-barrel fire hydrant. Conduct a hydrant flow test. Assist the pump driver/operator with drafting. Set up a portable tank.
Introduction • Primary objective at a fire – Get water on the fire • Hose line – Primary weapon for fighting fire – Fire fighter’s primary defense • Must have adequate supply of water to confine, control, and extinguish the fire © Jones & Bartlett Learning. Photographed by Glen E. Ellman.
Introduction • Water sources – Municipal systems – Static water • Water in tank on first-arriving vehicles used in initial attack • Establishment of adequate water supply becomes primary objective to support fire attack. © Glen E. Ellman.
Municipal Water Systems • Most owned by government • Some privately owned • Components – Water source – Treatment facility – Distribution system
Water Sources • Municipal water systems can draw from – Wells – Rivers or streams – Lakes – Reservoirs • Many systems draw water from several sources. • Source must be large enough to meet total demands of service area.
Water Treatment Facilities • Remove impurities • Nature depends on quality of untreated water source. • Water in system must be suitable for drinking. • Chemicals and UV radiation are used to kill bacteria and harmful organisms. © Hundley Photography/Shutterstock
Water Distribution System • Delivers water from treatment facilities to end users and fire hydrants through water mains • Also includes – Pumps – Storage tanks – Reservoirs – Other necessary components
Water Distribution Systems • Water pressure – Requirements differ depending on how water will be used – Ranges from 20 to 80 psi (138 to 551 k. Pa) – Recommended minimum pressure: 20 psi (138 k. Pa) – Usually produced by pumps – Most systems also use gravity © Jones & Bartlett Learning
• Elevated water storage towers maintain the desired water pressure in the distribution system. © Jones & Bartlett Learning. Photographed by Glen E. Ellman. Water Distribution Systems
Water Distribution Systems • Types of water mains – Primary feeders or trunk lines – Secondary feeders or branch lines – Distributors © Jones & Bartlett Learning
Water Distribution Systems • Size of water mains required depends on amount of water needed for normal consumption and fire protection – Fire fighters must know arrangement and capacity of water systems in their response area
Water Distribution Systems • Water mains typically follow grid pattern – Ensures adequate water flow – Minimizes downtime • Dead-end water mains – Found in older systems – Supply water from only one direction – Provide limited water supply
Water Distribution Systems • Control valves – Located throughout the system – Allow sections to be turned off or isolated • Shut-off valves – Shut off flow of water to individual customers or hydrants © Glen E. Ellman
Fire Hydrant Locations • Located according to local standards and nationally recommended practices – Every 500 ft (150 m) in residential areas – Every 300 ft (90 m) in high-value areas – Every intersection – Requirements may be based on occupancy, construction, and size of building • Knowing hydrant locations makes them easier to find in emergency situations.
Types of Fire Hydrants • Fire hydrants – Provide water for firefighting purposes – Installed on both public and private water systems – Consist of upright steel casing (barrel) attached to underground distribution system – Equipped with valves – Various outlet sizes – National standard threads
• Also known as frostproof hydrants • Used where temperatures fall below freezing Courtesy of American AVK Company Dry-Barrel Hydrants
Dry-Barrel Hydrants • Valve at base of barrel • Water enters only when needed • Turning operating stem opens valve © Jones & Bartlett Learning
Draining a Dry-Barrel Hydrant • After each use, water drains out through an opening in the bottom of the barrel. – When valve is open, drain hole is closed. – When valve is closed, drain hole is open. • Hydrants may not drain if they are clogged. • A fully opened hydrant allows for maximum flow.
• Used in warmer climates • Always water in barrel • Outlets controlled individually • Can add lines while water is already flowing Courtesy of American AVK Company Wet-Barrel Hydrants
Fire Hydrant Operation • Fire fighters must be proficient in operating fire hydrants. • Fire departments should ensure hydrant inspections and tests are performed regularly. • Always follow your department’s standard operating procedures for operating and shutting down fire hydrants.
Fire Hydraulics • Deals with properties of – Energy – Pressure – Water flow
Water Flow and Pressure • Water flow – Quantity of water moving through pipe or hose – Measured in terms of volume specified in gallons per minute or liters per minute • Water pressure – Amount of energy or force per unit area of water – Measured in pounds per square inch (psi) or kilopascals (k. Pa) – Pump increases pressure
Water Flow and Pressure • Energy – Potential energy (stored energy) – Kinetic energy (energy being used) – Moving water has combination of potential and kinetic energies
Water Flow and Pressure • To calculate volume of water flowing – Measure water pressure at center of water stream – Factor in size and flow characteristics of orifice – Pitot gauge • Measures water pressure in psi or k. Pa • Calculates volume of water in gallons or liters per minute
Water Flow and Pressure • Static pressure – Amount of pressure in system when water is not moving – Potential energy – Hydrant inoperable without it – Measure by • Placing pressure gauge on hydrant outlet • Opening hydrant valve
Water Flow and Pressure • Normal operating pressure – Amount of pressure in water distribution system during period of normal consumption – Measure by connecting pressure gauge to hydrant during normal consumption • Residual pressure – Pressure remaining in system when water is flowing – Decreases as more water flows
Friction Loss • Decrease of pressure that occurs as water moves through pipe or hose • Influenced by – Diameter of hose – Valves or hose appliances applied to hose – Volume of water traveling through hose – Distance water travels • Directly proportional to distance
Elevation Pressure • Created by gravity as water flows from hilltop reservoir to water mains in valley below • Also known as head pressure • Hose laid downhill – Water at bottom has additional pressure • Hose advanced upstairs – Loses pressure due to energy needed to lift water
Water Hammer • Surge in pressure caused by sudden stop of water flow • Can cause – Hose rupture – Separated couplings – Plumbing damage • Always open and close valves slowly.
Inspecting Fire Hydrants • Should be inspected at least once a year • Check for visibility and accessibility. • Check for exterior damage. • Ensure barrel is dry and free of debris. Courtesy of Captain David Jackson, Saginaw Township Fie Department.
• Ensure all caps are in good working order. • Open valve to verify water flow. • Shut down and ensure proper draining. • Replace cap. • Use steel brush to clean threads if necessary. © Jones & Bartlett Learning. Photographed by Glen E. Ellman. Inspecting Fire Hydrants
Testing Fire Hydrants • Requires – Two adjacent hydrants – Pitot gauge – Outlet cap with pressure gauge © Jones & Bartlett Learning • At the first hydrant – Place cap gauge on outlet. – Open hydrant valve. – Record initial pressure reading as static pressure.
Testing Fire Hydrants • At the second hydrant – Remove discharge cap and open valve. – Place Pitot gauge in stream and take reading. – Record as Pitot pressure. • Calculate flow availability based on readings. © Jones & Bartlett Learning. Photographed by Glen E. Ellman.
Rural Water Supplies • In areas not served by municipal water systems: – Residents rely on wells or cisterns for water. – No hydrants – Fire fighters must depend on water from other sources.
Static Sources of Water • Potential static sources – Rivers or streams – Lakes, ponds, or oceans – Canals or reservoirs – Swimming pools – Cisterns • Must be accessible to fire engine or portable pump © Jones & Bartlett Learning. Photographed by Glen E. Ellman.
Static Sources of Water • When the drafting location is identified – Inspect swivel gaskets. – Select and connect hose. – Place strainer on hose.
Static Sources of Water • Dry hydrant or drafting hydrant – Pipe with strainer at one end and connection for hard suction hose on the other end – Often installed in lakes and rivers close to clusters of buildings © Jones & Bartlett Learning.
Static Sources of Water • Dry hydrant or drafting hydrant – Connection should be a convenient height for an engine or portable pump hook-up – Often installed in lakes and rivers close to clusters of buildings – May enable fire fighters to reach water under frozen surface of lake or river Courtesy of Ryan Van Buskirk.
Static Sources of Water • Portable pump – Can be hand-carried or transported by offroad vehicle to water source – Can deliver as much as 500 gal (1893 L) of water per minute
Water Shuttle Operations • Tankers or water tenders – Transport large volumes of water to fires – Engines carry at least 500 gal (1893 L) – Tankers carry up to 3500 gal (13, 249 L) © IAN MARLOW/Alamy Images.
Water Shuttle Operations • Number of tankers needed depends on – Distance between fill site and fire scene – Time needed to dump and refill – Flow rate required at fire scene • Components must be set up so water moves efficiently from fill site to fire scene
Portable Tanks • • • Carried on fire apparatus Hold 600 to 5000 gal (2271 to 18, 927 L) Should be accessible from multiple directions One engine drafts water. Tanker fills portable tank. Pump operator begins drafting water. • Tanker leaves to get another load. Courtesy of Captain David Jackson, Saginaw Township Fie Department.
Portable Tanks • Dump valve allows offloading of water at rates up to 3000 gal (11, 356 L) per minute. • Additional portable tanks, tankers, and attack engines can be added quickly. © Jones & Bartlett Learning. Photographed by Glen E. Ellman.
Summary • The primary objective at a fire is to get water on the fire—the action that cools the fire and extinguishes it. • Municipal water systems draw water from wells, rivers, streams, lakes, or reservoirs; they carry the water via pipelines or canals to a water treatment facility and then to the water distribution system, a complex network of underground pipes.
Summary • Municipal water systems make clean water available to people in populated areas and provide water for fire protection. Fire hydrants make this water supply available to the fire department. • Most municipal water supply systems use both pumps and gravity to deliver water.
Summary • Underground water mains come in several sizes. Large mains, or primary feeders, carry large quantities of water to a section of a town or city. Smaller mains, called secondary feeders or branch lines, distribute water to a smaller area. The smallest mains, or distributors, carry water to the end users and to fire hydrants along individual streets.
Summary • Shut-off valves are located at the connection points where the underground mains meet the distributor mains. These valves can be used to prevent water flow if the water system in the building or the fire hydrant is damaged. • Fire hydrants are located according to local standards and nationally recommended practices. In many communities, fire hydrants are located at every street intersection.
Summary • The two types of fire hydrants are dry-barrel hydrants and wet-barrel hydrants. • Dry-barrel hydrants are used in areas where temperatures drop below freezing. When this type of hydrant is not in use, the barrel must be dry. • Wet-barrel hydrants are used in areas where temperatures do not drop below freezing. These hydrants do not have to be drained after each use.
Summary • Fire fighters must be proficient in operating fire hydrants, including the tasks of turning on the hydrant, shutting off the hydrant, and inspecting the hydrant. • To understand fire hydrant testing procedures, fire fighters must understand some basic concepts of fire hydraulics, which deal with the properties of energy, pressure, and water flow as related to fire suppression.
Summary • The water flow, or the quantity of water moving through a pipe, hose, or nozzle, is described in terms of its volume; it is usually specified in units of gallons (or liters) per minute. • Water pressure refers to the amount of energy or force per unit area of the water, and it is measured in units of pounds per square inch (psi) or in kilopascals (k. Pa). Water flow and water pressure are two different, but mathematically related, measurements.
Summary • Water that is not moving has potential (stored) energy. When the water is moving, it has a combination of potential energy and kinetic (in motion) energy. Both the water flow and the water pressure under a specific set of conditions must be measured when testing any water system, including fire hydrants.
Summary • A Pitot gauge is used to measure water pressure in psi (or k. Pa) and to calculate the volume of water in gallons per minute (liters per minute). • Static pressure is the pressure in a system when the water is not moving.
Summary • Because municipal water systems deliver water to many people, there is almost always some water flowing within the system. In most cases, a static pressure reading actually measures the normal operating pressure of the system. Normal operating pressure refers to the amount of pressure in a water distribution system during a period of normal consumption.
Summary • Residual pressure is the amount of pressure that remains in the system when water is flowing. • Knowing the static pressure, the water flow in gallons (liters) per minute, and the residual pressure enables fire fighters to calculate the amount of water that can be obtained from a hydrant or a group of hydrants on the same water main.
Summary • Static pressure is generally created by elevation pressure, pump pressure, or both. • Fire hydrants should be checked on a regular schedule of no less than once per year to ensure that they are in properating condition. • As part of fire hydrant testing, fire fighters measure static pressure and residual pressure at one hydrant and then open another hydrant to let water flow out.
Summary • In rural areas, fire departments often depend on water from static sources to maintain their water supply. • Water may be used from the static source directly or transported via a mobile water supply apparatus (tanker or tender). These trucks are designed to carry large volumes of water, ranging from 500 gal (1893 L) to 5000 gal (18, 927 L).
Summary • Dry or drafting hydrants and portable pumps provide alternative means of accessing static water sources in areas that are inaccessible to fire apparatus. • Portable tanks are carried on fire apparatus and can hold between 600 gal (2271 L) and 5000 gal (18, 927 L) of water. These tanks can be set up quickly and linked together to increase the water storage capacity.