Getting More Water to the Rural Fire
How the use of large-diameter hose, portable water reservoirs and tankers, can increase fire fighting potential at country fires
—Photo by Misiaszek Studio
The author of the following article is an active fire chief of an area embracing several volunteer fire departments. He has devoted much time and thought to the study of water supply problems inherent to rural fire protection.
His opinions on the use of large diameter hose, portable pumps, tankers and portable suction reservoirs are based upon first-hand experience with such facilities in actual fire fighting, as well as in experimental field operations.
ONE OF THE MOST IMPORTANT and vexatious problems facing the rural fire fighter today is that of securing adequate water supplies to further his attack on fires in areas devoid of municipal or other water sources.
The problem has been accelerated in recent years by the vast movement of business and industry and families into districts which, at best, had but limited water supplies and where provision for that precious essential has since received little consideration.
Although the fire service has been able to advance its own cause and its operations by the addition of such improvements as radio and telephone alerting, central dispatching, the use of water fog, wet water and a host of other equivalents, progress has not kept pace in securing for itself, this most essential of all extinguishing mediums—water.
The availability of sufficient water at the scene, unless the fire is located near some natural supply, is the result of careful planning as to apparatus, equipment and response. Study and application of some of the basic rules of the movement of water in lines and the performance of pumps can also assist in solving the problem.
Use of large diameter hose
Many of us tend to overlook the fact that by doubling the diameter of a conductor, we actually increase its capacity by four; and that by cutting the velocity of water in a line in half, it requires approximately one-quarter of the original pressure to move it.
There seems to be a tendency to try to overcome the problem of inadequate water supply by simply increasing pump pressure. The fallacy of this procedure lies in the fact that with a 500-gpm Class B pump—and this is a type common in rural areas—if we increase the operating pressure from 120 psi to 200 psi, we cut the output from 500 gpm to 250 gpm, and if we add another 50 pounds pressure, we cut it further to 167 gpm. In planning any water supply operation, one must keep in mind the pump’s ability to supply at the pressure required.
Let us consider the size of the conductor we use for a supply line. Assume that we need 300 gpm as an amount which will permit us to operate the equivalent of an Underwriter’s stream with some reserve. In 2 1/2-inch hose, 100 psi will move this amount of water about 500 feet. If we use 3-inch hose we find that 100 psi at the pump will move 300 gpm a distance of about 1,200 feet. But if we employ 3 1/2-inch hose we find that 100 psi pump pressure will move the same 300 gpm a distance of well over 2,000 feet. The latter distance is more in line with those frequently encountered at fires in rural areas. If we use the procedure of the pump at the water source supplying the pumper at the fire-ground and then let that apparatus apply the needed nozzle pressures, we find that we do not need extremely high-pressure pumps or heavy hose. This makes it possible to effectively use the smaller type of pump commonly found in rural departments, and by slightly increasing the hose size, just about double the amount of water may be obtained on long stretches.
Another very practical use of largediameter hose is in conjunction with portable pumps. These pumps are limited in their horsepower and any procedure which will reduce pressure requirements will greatly increase their effectiveness. Many departments use portables to move water from inaccessible sources to the pumper which then applies the pressure and delivers the water to the point where it will be used. Tests conducted with a typical portable pump which has a maximum flow of 250 gpm at 10 psi, showed that it was possible to move 246 gallons per minute a distance of 500 feet on the level with 3 1/2-inch hose. The pump operated at 12 psi as registered on the gage. This indicates that the large-diameter hose permitted it to operate at very near its maximum efficiency.
—Photo by Vernor T. Wetherell
Tank piping important
The area of the conductor plays an important part in still another application. This is in the suction line between the tank and pump on a tanker. To many people, a tanker is nothing more than a fire truck with a large booster tank. Nothing could be further from the truth!
A booster tank is designed to supply small lines for use in small fires or mop-up operations. A tanker’s purpose is to be the main source of water supply; its efficiency is directly associated with its speed and safety, combined with its ability to load and unload quickly. All too often we see a large, adequate chassis with a large pump and tank, but the suction line between the two is so small that much of its value as a supply tanker is lost because it can t unload quickly.
Equipment of this type should be designed with suction lines large enough to enable the truck to discharge at the rate of at least 250 gpm and even higher. A 2 1/2-inch gated inlet to the tank should be provided with an adequate overflow vent to allow maximum flow from a line of this size without causing a pressure rise in the tank. This arrangement will serve in at least two ways: First, it will permit the truck to be filled quickly if it is working in a shuttle; and second, it can work at the scene of the fire with a supply line from another tanker or a hose line connected directly to it. The tank will then act as a reservoir and tend to even out inequalities in the supply.
There are tankers of the type described operating in the field and doing a good job. In the most successful of these units, thought is given not only to the adequacy of the chassis from a safety and performance standpoint, but also to keeping a short compact design with a low center of gravity.
With the more recent elimination of many of the sources of complaint about front-end pumps, careful consideration must be given to the pump. Is the installation of a large midship pump worth the amount of water-carrying capacity it will displace? In many instances this can mean 300 to 400 gallons located in the best weight-carrying area of the vehicle. It is a problem of functional versus traditional design which can only be decided on the basis of need in the area.
Portable suction reservoirs
Another principle well worth considering in connection with water supply problems is the use of an open tank. When an open tank is used to pump from, the main problem is to balance nozzle output with supply, and all the problems of excess pressure, collapsed hose and interrupted supply are practically eliminated. This holds true whether the tank is a truck tank, a portable tank or a suction reservoir. The larger the; tank, the better the results; this is also so whether the water is delivered by hose line or truck shuttle.
Recently the use of suction reservoirs or portable tanks has received considerable attention in this country. The idea is not new; the British Fire; Service made considerable use of similar tanks during the last war and still does in areas where they are needed. One type of tank now being used in this country is a British importation which can be stowed in a space of 4 or 5 cubic feet in an ordinary compartment on a pumper or tanker. It is easily carried and erected by one man. This canvas tank is made in two sizes —3,000 and 6,000 gallons. There are also several types of varying capacities made in this country which have been used with success.
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Reservoirs of this type have the advantage of permitting incoming tankers to discharge their water upon arrival, either singly or in numbers without waiting, and to proceed immediately for more water. This affords maximum use of the tankers and makes it possible for a pumper to be used efficiently to supply the fire lines. Further, by using a largecapacity reservoir, lines may be operated for some time if tankers do not return immediately with water. This was the primary purpose for which the canvas tanks were provided in the begnning, but subsequent experience has proved they are valuable in relaying as well.
There is one point which is frequently overlooked when comparing reservoir operations of this type with a relay. When a tanker arrives on the scene it is ready to go to work immediately, as is each additional tanker as it arrives. However, in a relay, each truck must lay its hose, couple up suction and charge a long line. In the time it takes to do this, the fire most likely will make considerable progress and the stream may not be as effective as a lesser one would have been at the outset. Furthermore, in a relay, failure of just one length of hose—which is not an uncommon occurrence—or the failure of any one piece of equipment will make the entire relay 100 per cent ineffective. But in a tank shuttle, if one piece of equipment fails, the efficiency is cut only by the amount that the particular piece represents in the whole operation.
An excellent example of the use of reservoirs in relay work was provided at a demonstration held at the U. S. Submarine Base in New London, Conn., in May of 1957 (FJRE ENGINEEBINC October 1957). In this relay 15 engines, each pumping through 800 feet of 2 1/2-inch hose, supplied slightly more than 300 gpm a distance of more than two miles; the water was discharged through an open butt into a 3,000-gallon canvas tank. A pumper at the demonstration fire scene drafted from the reservoir and supplied the proper nozzle pressure.
Each pumper in the relay operated at a predetermined maximum pressure and when it was necessary to shut down the nozzle line to change tips, or for any other reason, 300 gpm continued to How into the reservoir and no complications were injected into the relay.
It was also possible to discharge amounts considerably in excess of 300 gpm for limited periods with this arrangement. The fact that not a single length of hose burst (with 240 lengths in use for over an hour) is in itself no small feat for an operation of this magnitude.
There is at least one other important use to which these large portable tanks can be put and that is as standby water supply for temporary hazards or during mop-up after a fire. By placing such a reservoir of water near the scene of a fire, it is possible to pick up and return to service most of the hose and equipment which has been used. At the same time any rekindle would be comparatively easy to cope with when a large supply of water is readily available.
While most of the equipment mentioned has originated in England or other European countries prior to, or during World War II, there is no reason to believe that all the items cannot be made here and most likely improved upon. What is necessary is a better understanding of the requirements and possibilities for supplying water in rural areas. Once this is done, there will be no problem in interesting manufacturers to produce the equipment.
Effective mutual aid a must
Even with the suggested innovations, there is the matter of mutual aid organization which is a vital necessity if operations of this kind are to be successful. In some areas it now exists; in others it must be developed.
In northeastern Connecticut, which is one area where mutual aid and central dispatching is highly organized, it is common practice to send an extra tanker on any structural fire alarm and follow the initial response with a tanker call which can put at least 5,000 gallons on wheels at the fire scene.
In these days manpower is a problem, and the ease with which a tanker arrangement can be put back in service becomes an important factor which cannot be overlooked when compared to picking up hose, cleaning and drying, and packing it back on the apparatus. A tanker need only refill and respond to another call, but a pumper with an empty hose body is not too valuable a piece to send to such a situation.
It is not a question of whether it is possible to do these things. The question is, are we willing to do the work and planning on the department and area level to assure success in moving effective amounts of water to the fireground!