3 Water. 3 Knowledge Objectives Describe the properties of water. Describe the three sources of water. Describe water’s role in extinguishing a fire

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Water

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Knowledge Objectives

• Describe the properties of water.

• Describe the three sources of water.

• Describe water’s role in extinguishing a fire.

• Describe static water pressure.

• Describe residual water pressure.

• Describe flow pressure.

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Skills Objectives

• Operate a hydrant.

• Shut down a hydrant.

• Demonstrate how to obtain the static pressure.

• Demonstrate the correct use of a Pitot gauge.

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Introduction

• Water supply must be dependable and adequate for fire suppression

• Ensuring a dependable water supply is a critical operation to be accomplished as soon as possible.

• Water is obtained from one of two sources:– Municipal and private water systems– Static water systems

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Chemical Properties of Water (1 of 7)

• 70–75% of the earth’s surface is covered by water.– Abundance means it is easy to take for

granted.

• U.S. Geological Survey says U.S. population consumes 408 billion gallons of water per day.

• Water is a virtually colorless, odorless, and tasteless liquid.

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• Many hidden qualities contained in the chemical description H2O– One atom of oxygen bound by two atoms of

hydrogen attached on the same side – Opposite electrical charges attract each other,

making water molecules stick to each other.– Surface tension allows water to flow, puddle,

or remain together even after leaving the nozzle.

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• Water dissolves more substances than any other liquid because of the strong bond between hydrogen and oxygen.– As water passes through or moves by a

substance, molecular charges take chemicals, minerals, and solvents with it.

– Substance dissolving into water is determined by whether the substance’s components can break water’s hydrogen bond.

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• Water has been used as the primary extinguishing agent in the fire service from the earliest days because of its availability. – Water can also absorb heat because of its

hydrogen-bonding characteristics.– Water absorbs almost five times more heat

than sodium bicarbonate.

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• Physical properties of water– Water exists in all three property states: liquid,

gas, and solid.– Water is the primary substance used to

extinguish fire because it turns to vapor (steam) when it comes in contact with fire.

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• Harmful characteristics of water– Pure H2O has a relatively low ability to

conduct electricity. – Turbidity is the amount of particulate matter

suspended in water.• Particulates settling in the pump housing and water

tank cause a breakdown of valves, gaskets, seals, and piping, which can lead to leaks and operational deficiencies.

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Municipal Water Systems (1 of 3)

• Make clean water available to people in populated areas– Provide water for fire protection

• Owned and operated by local government agency (city, county, special water district)– Some municipal water systems are privately

owned.

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• Municipal water is supplied to homes, commercial establishments, and industries. – Hydrants make the water supply available to

the fire department. – Most automatic sprinkler systems and

standpipe systems are connected to a municipal source.

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• Three parts– Water source– Treatment plant– Distribution system

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Water Sources

• Municipal systems draw water from wells, rivers, streams, lakes, and reservoirs.– Many systems draw water from several sources

to ensure a sufficient supply.

• Systems have storage facilities to ensure they will meet the demands of the area if the primary water source is interrupted. – Backup supply can provide water for months or

years.

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Water Treatment Facilities

• Remove impurities

• Water that is clean and clear from the source requires little treatment.– Some facilities use chemicals to remove

impurities and improve the water’s taste.– Chemicals are also used to kill bacteria and

harmful organisms.

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Water Distribution System (1 of 6)

• Delivers water from the treatment facility to end users and hydrants through water mains

• Distribution center includes pumps, storage tanks, and reservoirs to ensure the required water can be delivered where and when it is needed and at a required pressure.– Pressure requirements differ depending on water

use.– Systems rely on pumps to provide the required

pressure directly or indirectly.

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• Pure gravity-feed system– Water source, treatment plant, and storage facilities

on high ground while end users live in lower-lying areas

– May not require any pumps because gravity provides the pressure necessary to deliver the water

• Pumps may be used to deliver water from a treatment plant to elevated water storage towers or reservoirs on hills or high areas.

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• Combination pump-and-gravity-feed system– Must maintain enough water in elevated storage

tanks and reservoirs to meet anticipated demands

• Underground water mains that deliver water to end users come in different sizes.– Large mains: primary feeders that carry large

quantities of water to a town or city– Smaller mains: secondary feeders that distribute

water to smaller areas– Smallest pipes: carries water to users or hydrants

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• Size of water mains depends on the water needed for normal consumption and fire protection– Most jurisdictions specify a minimum size main

that can be installed to ensure adequate flow.

• A well-designed water main system follows a grid pattern.– Grid provides water flow to fire hydrant from

multiple directions

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• Control valves installed at intervals throughout the distribution system allow sections to be turned off or isolated.– Shut-off valves are located where

underground mains meet distributor pipes.– Can be closed to prevent further water flow

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Flow and Pressure (1 of 8)

• To understand procedures for hydrant testing, fire fighters must understand terminology. – Flow or quantity of water moving through a pipe,

hose, or nozzle is measured by its volume.• Usually given in terms of gallons (or liters) per

minute– Water pressure refers to an energy level,

measured in psi (or kPa).– Volume and pressure are two different, but

mathematically related, measurements.

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• Water not moving has potential energy– Water that is moving has potential and kinetic

energy.

• Static pressure is the pressure in the system when water is not moving.– Causes water to flow out an opened hydrant– Created by elevation pressure and/or pump

pressure

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• Static pressure is measured by placing a pressure gauge on a hydrant port and opening the hydrant valve.

• The normal operating pressure is the amount of pressure in a system during a period of normal consumption.

• Fire fighters need to know how much pressure is in the system when a fire occurs.

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• Residual pressure– Pressure in the system when water is flowing– Best indicates how much more water is in the

system– The more water flowing, the less residual

pressure

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• Fire fighters use the difference between static and residual pressure to determine how many attack lines or appliances can be operated from the available supply.– Tables developed to help calculate the

maximum amount of available water– Flow pressure measures the quantity of water

flowing through an opening during a hydrant test.

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• To calculate the volume of water flowing, measure the pressure at the center of the water stream passing through an opening and factor in the orifice’s size and flow characteristics.– Pascal’s law: pressure acts in all directions

equally– Bernoulli’s equation: defines friction loss as a

drop in pressure while water maintains velocity

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• Knowing static pressure, flow in GPM (L/min), and residual pressure lets the fire fighter calculate water that can be obtained from hydrant or hydrants on the same water main.

• Gravity exerts its effects on flowing water based on the stream’s elevation and altitude.– Elevation is the position of the pump (above or

below) compared to the nozzle.– Atmospheric pressure changes depending on

location.

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• Water hammer– Pressure surge or wave from kinetic energy of

fluid in motion when forced to stop or change direction suddenly

– Quickly closing valves, nozzles, or hydrants can create damaging pressure spikes.

• Liquid is not compressible.– Any energy applied to it is instantly

transmitted back through it.

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Fire Hydrants (1 of 6)

• Hydrants provide water for firefighting. • Public hydrants are part of a municipal

system and draw water from public water mains.

• Hydrants on private water systems are supplied by a municipal system or a separate source. – Identify source, adequacy, and reliability of

supply to ensure hydrants will be sufficient

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• Most hydrants consist of a barrel attached to an underground water distribution system.

• Hydrants are equipped with one or more valves to control water flow through the hydrant.

• One or more outlets connect the fire department hoses to the hydrant.

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• Dry-barrel hydrants are used where temperatures fall below freezing. – Valve controlling water flow into the barrel is

located at the base, below the frost line – Barrel length depends on climate and depth of

valve– Water enters the barrel only when it will be

used.– When not in use, the barrel must stay dry.

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• Dry-barrel hydrants (continued)– A partially opened valve means the drain is

also partially open and pressurized water can flow out.

– Most dry-barrel hydrants have only one large valve controlling water flow.

– Trash or foreign objects in empty dry-barrel hydrants can obstruct water flow or damage the fire department pumper.

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• Wet-barrel hydrants are used where temperatures do not drop below freezing. – Always have water in the barrel– Not drained after each use– Wet-barrel hydrants have separate valves to

control flow to each outlet.

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Courtesy of American AVK Company

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Operation of Fire Hydrants

• Fire fighters must be proficient in operating a hydrant.

• Individual departments may vary procedures for opening a hydrant. – Follow SOPs for your department.

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Shutting Down a Hydrant

• Shutting down a hydrant properly is just as important as opening a hydrant properly. – Hydrant damaged during shutdown cannot be

used until it is repaired

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Locations of Fire Hydrants (1 of 2)

• Hydrants are located according to local standards and nationally recommended practices. – May be placed a certain distance apart

• Every 500’ (152 m) in residential areas• Every 300’ (91 m) in high-value commercial and

industrial areas

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Locations of Fire Hydrants (2 of 2)

• Some requirements for locating hydrants are based on building occupancy, construction, and size. – Builder may have to install additional hydrants

so no part of the building is more than a specified distance from the closest hydrant.

– Knowing the plan for installing hydrants makes them easier to find in emergencies.

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Inspecting and Maintaining Fire Hydrants (1 of 5)

• Hydrants are essential to fire suppression efforts so fire fighters must understand how to inspect and maintain them. – Check hydrants regularly. – During inspections, fire fighters may

encounter common problems and should know how to correct them.

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• Check for visibility and accessibility. – Hydrants should be visible from every direction.– Bright reflective colors are effective.– Should not be hidden by tall grass, brush,

fences, debris, dumpsters, or other obstructions– No vehicles should be allowed to park in front of

a fire hydrant.– Should be installed at an appropriate height

above the ground

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• Check the exterior for signs of damage. – Open the steamer port of a dry-barrel hydrant

to ensure the barrel is dry and free of debris.

– Make sure all caps are present and outlet hose threads are in good working order.

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• Ensure the hydrant is working properly.– Open the valve wide enough to ensure that

water flows out and flushes debris out of the barrel.

– After flushing, shut down the barrel.– When a hydrant is fully drained, replace the

cap on the wet-barrel hydrant.– Check gaskets in gaps to make sure they are

not cracked, broken, or missing.

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Testing Fire Hydrants (1 of 5)

• Water that is available to fight a fire at a location is crucial in planning an attack.

• Fire companies are often assigned to test hydrant flow. – Testing procedures are simple but require a

basic understanding of hydraulics and careful attention to detail.

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• Fire hydrant testing procedure– Requires two adjacent hydrants, a Pitot gauge,

and an outlet cap with a pressure gauge– Place the cap gauge on one outlet of the first

hydrant. – Open the valve to let water fill the hydrant

barrel. – Record the initial pressure reading on the

gauge as static pressure.

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• Fire hydrant testing procedure (continued)– At the second hydrant, remove one discharge

cap and open the hydrant. – Use the size of the discharge opening (usually

2½” [51 mm]) and Pitot pressure to calculate the flow or look it up in a table.

– Devices are available to simplify the process of taking accurate Pitot readings.

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Rural Water Supplies (1 of 4)

• Many departments protect areas not serviced by municipal water systems. – Residents depend on individual wells or

cisterns to supply water. – There are no hydrants, so fire fighters must

depend on water from other sources.

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• Static sources of water– Several potential sources can be used for fighting fires

in rural areas. – Both natural and human-made bodies of water can be

used. – Water from a static source can be used if it is close

enough to the fire scene.– Water must be transported using long hose lines,

engine relays, and mobile water supply tankers

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• Static sources of water (continued)– Static water sources must be

accessible to a fire engine or portable pump.

– Dry hydrants provide quick and reliable access to static water sources.

• Portable pump is an alternative means of obtaining water

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Summary (1 of 3)

• Fighting fires depends on adequate water to confine, control, and extinguish the fire.

• Ensuring a dependable water supply is a critical operation to be accomplished as soon as possible.

• Water comes from a municipal or private water system.

• Municipal water systems make clean water available to people in populated areas.

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Summary (2 of 3)

• Wet-barrel hydrants are used where temperatures do not drop below freezing.

• Dry-barrel hydrants are used where temperatures fall below freezing.

• Hydrants are located according to local standards and nationally recommended practices.

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Summary (3 of 3)

• Fire fighters must be proficient in operating a hydrant, including turning on and shutting down.

• Hydrants are essential to fire suppression efforts so fire fighters must understand how to inspect and maintain them.

Documents

3 Water. 3 Knowledge Objectives Describe the properties of water. Describe the three sources of water. Describe water’s role in extinguishing a fire