Article and photos by Paul Shapiro
The result of any fireground water-delivery operation is to provide the required volume of water in the form of effective firefighting streams to reach and overwhelm the British thermal units (Btus) of the fire, achieving a knockdown as quickly and as safely as possible. This holds true for the smallest to the largest fires to which firefighters respond. It is relatively easy to provide an adequate water supply for the small fires. However, large-scale, surround-and-drown scenarios can necessitate large volumes of water that must sometimes be delivered in complicated hose evolutions.
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Two distinctive types of large fires fall under the large-flow water-delivery category. The first is the standard and probably most common of large fire scenarios. It involves structures that are completed and that may be occupied or unoccupied. These fires are usually fully involved; however, because they are completed structures, they tend to sometimes limit the progress of the fire spread to exposures, allowing firefighters to get the upper hand.
(2)薪酬leted structures offer more resistance to extension to exposures.
The second type of large fire problem that presents itself, to a lesser degree, is the open-area type, such asconstructionsites that have unfinished open walls, lumberyards, and other large areas of combustibles. These types of fires need a fast attack with a lot of water to gain the upper hand because of the great threat to exposures.
(3) Uncompleted structures, such as those found at construction fires, need to be attacked rapidly to stop the fire from spreading to other structures.
It was easier to understand having a water supply problem in the past when fire departments used 2½- and three-inch supply lines. Multiple lines would have to be laid quickly to move the water supply. Since most the fire departments have large-diameter hose (LDH), also known as the miracle hose, above-the-ground water mains, and so on, etc., why are we still having water-supply problems in the middle of town with hydrants around for miles and enough engines and hose to get the job done? LDH has had a positive effect on the fire departments’ capabilities to move water. At the same time, it has led us to think that the hose itself is a cure-all—all we have to do is lay one of these big lines from a hydrant to the fire to bring in all the available water that can be delivered. Unfortunately, this is not so. LDH has restrictions, but we can deal with them.
Indications of Water Supply and Delivery Problems
There are three main indicators of pending and imminent water-supply and water-delivery problems on the fireground. The pump operator probably would be the first to notice signs of a potential water-supply problem. By monitoring the intake gauge on the pump panel, the pump operator can be alerted of a possible problem by a low intake residual pressure. The pump operator should also be keeping an eye on the supply line at the intake, making sure that the hose is not going soft or is completely flat. It is important that you don’t wait for these signs to identify a problem.
(4) A low intake pressure is an indication of low water.
(5) Monitoring the supply line can tell you a lot.
Ineffective fire streams in volume or reach is another sign of a water-delivery problem. It can be caused by a shortage of water, an improper pump discharge pressure, incorrect nozzle choice, or an improper supply or discharge hose evolution. Whatever the cause, the bottom line is that it is a water supply and delivery problem that needs to be fixed. Let’s look at some of these problems.
(6-7) Poor stream performance is a water-delivery problem.
Causes of Water-Supply and -Delivery Problems
A high percentage of water-supply and -delivery problems can be overcome. Overworked engine companies can create a water-delivery problem that can also affect fire streams that are in service as well as prevent the deployment of additional streams. High-flow pump operations can push pumps to the maximum by hitting the governed speed of the engine (revolutions per minute) or by maxing out the pump panel throttle’s mechanical travel capability.
(8) A single engine company can be taxed for horsepower when delivering multiple streams.
(9) Additional engines should be assigned to share the workload as needed.
A water supply problem can be caused by a hydrant’s inability to produce the water and pressure. Some of the reasons may include a lack of hydrants, low-volume or low-pressure hydrants, small water mains, and dead-end water mains. These problems can usually be dealt with through the proper hose and pump evolutions. However, often, improper hose and pump evolutions allow the deficits of a poor hydrant system to create a water-supply problem at the fire. Photos 10-16 illustrate some common improper hose evolutions.
(10) The following photos demonstrate some common improper hose evolutions. Long lines supplied directly from a hydrant create friction loss that taxes the hydrant system’s pressure under high-flow requirements.
(11) Using small-diameter hose instead of LDH.
(12) Improper discharge use.The rear 2½-inch discharge being used for high flows. The rear 2½-inch discharge has a high friction loss because of its long 2½-inch plumbing needed to bring the water from the pump to the rear.
(13-14) Improper intake use. The front suction and the 2½-intake are insufficient for flowing big water.
(15-16) Improper apparatus placement. Engines supplying water to a truck company’s elevated stream should be as close as possible. Long discharge lines can rob the pressure needed to produce the proper stream.
Large-flow water-delivery hose evolutions can be complicated to set up, thus creating a time-consuming process that can directly affect how quickly water is delivered on the fire. The infrequency of large fires coupled with the difficulties of having large-scale water-delivery drills directly affects our knowledge and competency to do big-water operations.
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Often, large flow-water delivery operations can get complex and may need heavy radio traffic to manage it. This can indirectly cause freelancing and confusion for the pump operators and even more radio traffic, contributing to an already busy situation. If possible, have a separate radio channel for the water-delivery operations.
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As mentioned, a large-scale water-delivery operation can be chaotic. A structured system of command that included the position of water management officer (WMO) needs to be implemented. The WMO will oversee a group of personnel whose main purpose is to provide the water requirements for the fire operation.
It is of the utmost importance that the WMO has a thorough knowledge of all supply and discharge evolutions and the ability to implement the duties of the WMO.
The WMO is a mobile position in that he or she is on thefireground, not at the command post, and us doing radio and face-to-face communication with all personnel involved with the operations (photo 18).
(17)
When pump residual pressures start to get low and there is a chance that more fire streams will be needed, don’t wait until units run out of water. Develop additional water supplies to the units in need from specific hydrants on separate mains. The hose evolutions needed to do this can include relay pumping, dual pumping, looped supply lines, and secondary supply lines. Assign additional units to develop these new pump operations as needed.
协助完成所有人员参与the water delivery operations if the need it. This may involve issues not related to the water-delivery operation such as the need for a restroom break, food, fuel for apparatus, and so on.
PAUL SHAPIRO, a member of the fire service since 1981 and a retired engineer from the Las Vegas (NV) Fire Department, is director of Fire Flow Technology and a national instructor on large-flow water delivery. He has authored numerous articles for fire trade magazines and a video on large-flow water delivery.
Originally ran May 31, 2017.
