How Much Water Can You Move
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APPARATUS
Like any other operation, transporting a rural water supply requires drills.
Unsure of which fire protection district he lived in, a frantic homeowner in a rural community called two neighboring volunteer departments when he discovered his house on fire. Four tankers and three engines from the two departments arrived at the same time. With plenty of water immediately available, a deluge gun was able to pour 1,000 gallons of water a minute onto the blaze for the first two or three minutes. Together by coincidence, the departments were able to put out the fire and save a property that otherwise would have been a total loss.
In another incident, the two tankers that responded were unable to keep up with the 800 to 900 gpm required to bring a fire under control. A property that might have been saved with minimal damage was, instead, lost.
Much has changed in the dozen or so rural communities off the northeast end of Oneida Lake, 20 miles north of Syracuse, N.Y., since these two incidents in the early 1980s. Coincidence in one and disaster in the other created insight into water supply needs.
In cities and suburban areas, hydrant systems provide a reliable source of water, and calculating how much water is available at various pressures can be done in a fire flow test.
In a rural setting without hydrants, where fire departments depend on tankers as the water source, a different approach is required. Once you know what the required fire flow is, you have to determine what your pumpers and tankers are capable of delivering to the scene. And because the water must be hauled from its source, travel time becomes important in calculating the number of tankers required.
Working with these factors, you can design what should be an interesting and informative training session for your own people and the fire departments with which you have mutual-aid agreements.
The volunteer fire company in Central Square, N.Y., conducted such a drill for a dozen companies within a 20-mile radius, all volunteers from towns with populations ranging from Williamstown’s 400 to Central Square’s 2,000.
Set up to simulate their normal response times to Central Square, which are as long as 30 minutes, the drill involved 12 departments with 13 tankers. It determined how much water they could actually deliver to a 75,000-square-foot strip shopping center located about one mile from the nearest water source in the town’s fire protection district.
With the tank sizes already known, records were kept of the number of loads hauled and the time it took to unload at the simulated fire scene. Times were taken as the units entered the area at a fixed point close to the scene. The clock ran until they reached the same point after unloading, on their trip for another load of water.
During the 90-minute exercise, 135,000 gallons of water were transported, resulting in an average flow of 1,500 gpm.
For planning purposes, most authorities suggest reducing the capacity figure by 20 percent to account for spillage, the fact that tankers are seldom totally emptied at the fire scene, and the fact that the design of water tanks usually means a small amount of water remains unpumped. By that standard, a 2,000-gallon tanker must be credited as delivering 1,600 gallons of water.
In the Central Square exercise, the actual delivery rate would be 1,200 gpm, or slightly less than 100 gpm per tanker used.
That lesson has been demonstrated time and again in the series of exercises our departments have conducted together during the past five years; this exercise last April simply reinforced what we’ve learned:
- The most efficient and rapid unloading method is large dump valves relying on gravity to move the water. Flow rates run about 100 gpm per inch. Dump valves of less than 10 inches can mean standing and waiting several minutes while a tank empties; dump valves of 12 inches or more can empty most rural department tankers in less than two minutes.
- Simple operations work best. The “super dumper” valve measures 16 by 16 inches, is air-operated from the cab in a one-person operation, and delivers 2,200 gallons in less than 45 seconds.
- Units with extension tubes that must be connected manually require either a second firefighter or the driver to spend time with activities that don’t improve the tanker’s dump-time efficiency.
- Enclosing the dump valve inside a compartment adds unnecessary steps to the dumping procedure. The firefighter must open the door, climb into the rear compartment, operate a lever to start and finish unloading, climb down, and close the door before leaving to refill the truck. The procedure is both slow—reducing the delivery rate—and potentially dangerous.
- Personnel requirements can be minimized by using power-op-
New Life,New Load
Volunteer fire companies generally have a reputation for their ability to make do and improvise. Frequently, they have no other choice.
The list price on a shiny, new, 2,000-gallon tanker, for example, can be about $70,000.
For a department in a small community such as Cleveland, N.Y., with 1,000 residents and an annual fire company budget of less than $40,000, purchasing this one piece of essential apparatus new is a virtual impossibility.
Cleveland’s solution was to buy and completely overhaul an older fuel oil tanker. The nearby West Monroe company has two; Cleveland’s fire department is making its second conversion.
This isn’t a process of simply buying an old truck, flushing and washing the tank to get rid of the fuel oil, and repainting the body.
First of all, fuel oil tankers weren’t designed to carry water. Strange as that may sound, it’s true. Fuel oil weighs only 80 percent as much as water—7.3 pounds per gallon compared to 8.5. In a 2,000-gallon tanker, that difference can add 2,400 pounds to the load when water is on board instead of fuel oil.
So the conversion has to start with strengthening the chassis; putting in springs, shocks, and tires that can handle the heavier load; and installing bigger brakes.
Before you start, of course, you’ll want to make certain you know the engine is up to hauling the equivalent of a mediumsized automobile in additional weight. You don’t want to have to dump 300 gallons or more along the road to make it to the top of the first real hill you encounter.
An extra precaution is necessary in driving the apparatus: Because the tank doesn’t have baffles inside, the rig should be driven only full or empty, to prevent the dangerous sloshing that can occur inside a partially full tank.
Cleveland, like many other departments, can tap a wealth of talents among its volunteers. In the department’s first experience converting a fuel oil tanker, it spent about $3,000 for the truck itself, not much more than its salvage value. Not including the value of the contributed labor, the actual out-of-pocket costs ran another $7,000.
The department is making a second conversion, proceeding as the volunteers’ time permits. When it’s finished, the department will have two tanker trucks for about half the price of a new one.
The way we see it, our service to the community doesn’t start when the fire alarm goes off.
(Photo by Jack L. Cottet)
- erated valves. Only the tanker driver is needed to operate them. This frees a second firefighter for other work. If the driver can stay inside the cab of the tanker observing a tank gauge, rather than leaving and then reentering the vehicle after the tank is empty, total water delivery efficiency can be improved.
- In too many cases, more time is spent making and breaking connections for dumping and filling than in the actual loading and unloading. Quick-connect couplings should be used whenever possible.
- The size of the air inlet valve also plays an important role in how quickly tanks using the same size dump valve are able to get rid of their loads. At the extremes in this test, one truck was more than nine times as efficient, effectively allowing it to deliver more water to the scene than a truck with a larger tank capacity.
In the half dozen years since coincidence and disaster provided the opportunity for new insights, our area’s rural fire departments have taken many steps to improve their efficiency.
The small dump valves are gone. The 6-inch valves are being replaced as the limited budgets of volunteer departments permit; more units are being converted to use 10-, 12-, or 16-inch valves.
The method of refilling tankers has also changed from using hydrants and minipumpers to using full-size pumpers; getting water into tankers quickly is just as important as getting it out of them quickly.
And rather than having full tankers waiting in line, like people standing in a bucket brigade, to unload into a single, portable folding tank, the departments are now using multiple folding tanks.
The goal is always to have tankers loading, unloading, or traveling, never simply sitting and waiting.
Without enough apparatus, firefighters will run out of water. So the pattern of responses has changed as well, calling tankers from mutual-aid departments as part of the first response in order to have a more-than-adequate water supply available as part of the initial attack. Calling tankers in batches provides fresh supplies for a second and, if necessary, a third attack while the first tankers are reloading. It’s a procedure designed to prevent disaster.
Rural firefighters owe it to themselves and the people they protect to try such procedures and practice the techniques of water movement using tankers. Preparation provides insight, too.
