There are several valid reasons why fire departments need to buy big pumps, more than 1,250 gpm.
First, if the department drafts water from great horizontal distances, 70 to 80 feet, or from very deep lifts, 15 to 27 feet, big body pumps will supply several hundred more gallons per minute than the smaller body pumps. As you reduce the fire pump flow, it generates more vacuum at its eye, allowing you to draft at a lower than rated flow, under severe conditions.
We could easily be looking at the difference of 300 to 400 gallons per minute. For the same reasons, if your department is located at a high elevation, 5,000 feet plus, the big body pump will out perform the small body pump from draft.
Even operating from a hydrant, the big body pump allows more water to go through the pump with less losses, lowering the engine operating speed and providing more available flow.
Other things to consider are that big pumps operate at lower engine speeds, reducing noise, wear and fuel consumption. Also, keep in mind some departments don’t have many apparatus to divide into their ISO rating. A big pump is helpful in reducing this.
Consider whether the apparatus is feeding an aerial device waterway, since the required flow will need to be supplied at approximately 220 psi. If you only have low-pressure hydrants, or must draft the bigger flow at these high pressures, a big pump would be welcomed.
From draft, a big pump, given a reasonable engine, will produce 1,500 gpm at 220 psi or more. A small body pump will not do this.
In today’s structural firefighting world, we seem to have two types of fires, one that takes a couple of hand lines or, at most, a personal monitor with flows of 300 to 800 gpm. The second type are the really big ones which need an elevated water way and big monitors to keep from eating city blocks or entire shopping malls.
For those departments that only have the first type, small fires, then the smaller pumps make perfect sense.
However, if you ever find yourself needing a big master stream with high flows, you need the bigger pumps. If you are using master streams, your main power requirements are less than a lot of hand lines.
The big pumps also leave room for wear. A big body midship is a 2,000 gpm pump, which is sold normally with a rating from 1,250 gpm to 2,000 gpm. If you buy a small body, 1,250 gpm midship pump, it’s only a 1,250 pump with a rating of 750 to 1,250 gpm.
The price consideration is very small, only a couple of thousand dollars, between a 1,500 gpm pump and a 1,250 gpm pump. There are very few trucks that have less than 300 hp engines, which is plenty big enough to easily power a 1,500 gpm, and probably even a 1,750 gpm pump.
Today, it seems departments are buying more discharges than they truly need to meet the 1,500 gpm ratings. How many big fires will a department fight over the truck’s lifespan? Even if it’s just one, spending the extra money was worth it. You might even get a couple of extra years of life from it because of reduced wear and tear. Then it makes perfect sense, economically.
Whether you are a paid or volunteer department, the apparatus must satisfy the firefighters needs, on a practical and an emotional level. Today, we see very few really “Plain Jane” trucks. Why is that? Because volunteers are easier to recruit and retain if the apparatus they’re expected to use is attractive and performs beyond expectations. Even career firefighters tend to take better care of apparatus they like better. Having a big pump is an emotional thing in some departments.
Dominating The Market
Here are some interesting notes on pumps to consider.
Pumps with National Fire Protection Association pumps rated at 1,250 gpm and 1,500 gpm overwhelmingly dominate the North American major fire pump market.
Big manifold, midship pumps commonly referred to as big body pumps, which can be rated up to 2,000 gpm, dominate the 1,500 gpm rated pump portion of that market. Big body pumps have the same parts whether they are rated at 1,250 gpm, 1,500 gpm, 1,750 gpm or 2,000 gpm.
Most customers realize this fact and buy 1,500 gpm rated pumps knowing they have added performance and a longer lifespan. The advantage of ordering the 1,500 gpm rating instead of the 2,000 gpm rating on these big body pumps is in the yearly service test. Only one set of suction hose is needed to do the 1,500 gpm test, but you need two sets for 1,750 gpm or 2,000 gpm testing. Adding to this, the customer realizes that if they need more performance, just throw on the second hose set and you have a 2,000 gpm pump.
Horsepower Requirements
Most 7 and 8 liter engines, producing 320 to 330 hp, will easily handle a 1,750 gpm pump test, topping out at 1,850 to 1,900 gpm drafting. A 9 liter engine, producing 350 to 400 hp will handle a 2,000 gpm pump test, topping out at 2,200 gpm. The top-out flow depends on ideal suction conditions and available engine power. There are some trucks with restrictive engine cooling systems causing the engine computer control to lower the available power. You may think you bought a 400 hp engine, but it may only give you 350 hp once the truck is at full operating temperature.
Now, to bring all this information to reality, some departments should buy the 1,500 gpm big body pumps, even though they do not need big flows, simply to improve the drafting performance available during some conditions.
If you have no water source, no mutual aid and limited staffing, you probably need a pumper/tanker with a 750 gpm pump and a 3,000-gallon tank.
Unfortunately, in the United States, buildings are built to burn and, in economically challenged areas, row homes are the norm.
Until we have better building codes and inspection, advanced building construction practices, residential sprinklers, and public education programs available to everyone, we still need big pumps.
Editor’s Note: Gary Handwerk has been involved with the fire service industry for 35 years working for various fire apparatus or fire pump manufacturers. He is currently Global Pump Product Manager for Hale Products and has been a member of the National Fire Protection Association (NFPA) Fire Apparatus Standards Committee for 15 years.
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