Doug Leihbacher

Photo by: Michael Messar, Yonkers Police Department

The pump operator’s job is one of the most mentally demanding on the fire ground. It requires skill, confidence, and attentiveness. The success of all other fire ground operations often depends upon the pump operator’s ability to supply water in a timely manner. The first few minutes after arrival can be demanding. For instance, at a recent occupied multiple-dwelling fire showing two floors of fire on arrival, the third arriving engine company’s pump operator was ordered to immediately supply:

a 250-foot, 1¾-inch pre-connect going into back up the first due engine;
a 2½-inch handline taken by the second due engine to cut off the fire in the alley on the exposure No. 4 side; and
two 3½-inch supply lines going to the tower ladder in front of the fire building by orders of the battalion chief.

These three tactical measures were ordered immediately upon arrival by three different fire officers before the pump operator had an opportunity to attach the two supply lines from the hydrant. Thanks to his good skills and training, everything went off without a hitch.

Often, there is a lot riding on the skills of the pump operator. He has to think on his feet and work without direct supervision. While things can get pretty complicated, the basic concepts are pretty straightforward; and it is good to have an understanding of them. In this article, we will review the basic concepts that underlie pump operations and discuss the priorities and procedures of a hands-on pumping operation. A good place to begin is with definition of terms, starting with “flow.”

FLOW — Flow is the amount of water being delivered to the burning material, measured in gallons per minute (gpm). The minimum recommended flow for a handline operating inside a building (except during overhaul) is 150 gpm.

PRESSURE — Pressure is the force with which the water is moving. It effects the flow and reach of the hose stream. As the pressure goes up, the flow and reach increase within the limits of the nozzle and hose being used. It is measured in pounds per square inch (psi).

INTAKE/DISCHARGE PRESSURE — Intake pressure is the pressure coming into the pump from the hydrant. Add to it the pressure created by the rotating impellers of the pump in order to yield the pump discharge pressure. The intake pressure should not be allowed to drop below 15 psi. This is your cushion to prevent drawing a vacuum and cavitating the pump.

FRICTION LOSS — This is the resistance met by the water as it travels through a hose line. The narrower the hose, the greater the friction loss. Also, the longer the hose stretch, the greater the friction loss. Friction loss is generally measured in psi per 100 feet. It is can also be measured in psi per length.

HEAD LOSS — This loss in pressure is due to gravity, and is measured as 5 psi per story of building height. Head can also be gained if the pump is above the level of the fire, as in pumping into a sub-basement.

SYSTEM LOSS — This pressure loss occurs when pumping into a sprinkler or standpipe system. It is caused by the restrictions created by the valves and internal bends in the siamese and piping. The rule of thumb used most often is 15 psi system loss.

NOZZLE PRESSURE — The optimal pressure needed at the nozzle in order for it to produce an effective stream. Based on nozzle design, the nozzle pressure varies with the type of nozzle:

PUMP DISCHARGE PRESSURE — This is the pressure at the pump needed to overcome friction loss, head loss and system loss in order to supply the nozzle at its rated pressure. Pump discharge pressure, a.k.a. “pump pressure” or “engine pressure,” is always greater than nozzle pressure. Thus the formula:

Of these, nozzle pressure and friction loss are the most important to consider initially. Remember also that these pressures are flowing pressures, not static pressures. They are to be adjusted when the nozzle is open. When the nozzle is shut off, the gage reads the static pressure, which is always higher.

In the above-sighted incident, with three orders given at once, what are the priorities that the pump operator should follow? The first priority is to supply the handline going into the fire building. These members are at the greatest risk and should be supplied with water from the tank as soon as they call for it. The second priority is to get one supply line from the hydrant into the pump. Without hydrant water, it will be impossible to supply the handline in the building and the exposure line in the alley for more than one minute. Once the supply line from the hydrant is charged, the 2½-inch exposure line should be charged. The supply lines to the tower ladder can be stretched by the truck crew immediately, but they should not be charged until hydrant pressure is established. While it is not generally considered good practice to supply a handline and master stream from the same pumper at the same time, it should be remembered that the tower ladder will not be put into operation until the handlines have been shut down and withdrawn from the building.

a) When arriving on the scene, water is usually supplied from the onboard water tank first and then from the hydrant, after the hook up is completed.

b) When the officer calls for water, charge the hoseline from the tank immediately, even if the hydrant isn’t hooked up yet. Advise the officer that you’re working off the tank, and give updates relating the amount of water remaining in the tank. A 500-gallon tank will provide 3½ minutes of continuous operation at 150 gpm—plenty of time to hook up a supply line. Remember to throttle down when switching to hydrant pressure.

c) Once you switch over to hydrant pressure, “crack” the tank fill valve and refill the tank so that if the hydrant supply fails, you can give the interior crew the tank to work off of while the problem is being dealt with.

d) Gauge how good the hydrant is. Does the intake pressure drop substantially when the nozzle is opened or does it hold pretty steady? This will indicate how many additional lines can be supplied from your pump. Use caution not to allow your residual pressure to drop below 15 psi on the intake gage. In cases where the demand outstrips the water available to your pump, advise the officer that you cannot supply what he needs without drawing a vacuum unless another engine provides you with additional water.