LARGE-DIAMETER HOSE: ADVANTAGES AND DISADVANTAGES

LARGE-DIAMETER HOSE: ADVANTAGES AND DISADVANTAGES

WATER SUPPLY

Fire departments throughout North Carolina are equipping their apparatus with large-diameter hose. Overall, they feel that the benefits of larger hose outweigh the drawbacks.

Over the past two decades the fire service gradually has been accepting the use of supply hose with diameters greater than 2 1/2 inches. Since greater volumes of water can be moved through large-diameter hose, fewer supply lines are required and spaghetti has been disappearing from the fireground as departments lay 3,4 and 5-inch supply lines.

Large-diameter hose has proven effective in both urban and rural settings, but a department considering the change should be aware of both the advantages and the new problems that it might encounter. Although 3-inch hose is not universally considered to be large diameter, even a slight increase in the diameter of a supply line causes a dramatic increase in the amount of water available through the hose. Increasing the diameter of hose increases the cross-sectional area by the square of the radius (area = πr2) resulting in reduced friction loss. The cross-sectional area of 3-inch hose is actually 44 percent larger than that of 2 1/2-inch, and 4-inch hose is 156 percent larger than 2 ¼ -inch. Friction loss in 4-inch hose is 11 times less than in 2 1/2-inch. Use of largediameter hose consequently allows longer lays of hose and lower operating pressures.

In an area with frequent spacing of hydrants and moderate water supply capabilities, a fire department using a 2 1/2-inch supply line can deal adequately with the average dwelling fire. However, if the dwelling is especially large or has a long driveway, the situation calls for dual lines, relay pumping, or larger diameter hose. In an industrial setting, the need for large volumes of water through long hose lays is more often the rule than the exception. This can lead to costly delays if water cannot be applied promptly. In either example, large-diameter hose could make the difference between quick fire control and extensive fire losses.

Many municipal and rural fire departments in North Carolina lay 3-inch supply lines, and several lay 4-inch and 5-inch line in their routine operations.

In 1971, the Charlotte, N.C., Fire Department conducted a series of tests on 5-inch supply lines in conjunction with the National Fire Protection Association. The department found that a 1000-gpm pumper could deliver its full rated capacity using a single 5-inch supply line 1000 feet from a hydrant without relay pumping. Because of these findings, the department supplemented its standard 2 1/2-3-inch split hose loads carried on its engines with a hose tender carrying 1000 feet of the 5inch hose. According to Charlotte Fire Chief R. L. Blackwelder, the 5-inch hose was used successfully on a number of larger fires, prompting the department to experiment with putting larger diameter hose on a pumper.

In 1974, 1000 feet of 4-inch, polymer jacket hose with sexless, Storz couplings was put in service in Charlotte’s busiest engine company. Four-inch hose was selected because the 5-inch size would not fit into a standard hose bed in the 1000foot load that was required in some areas of infrequent hydrant spacing. The 4-inch hose was found effective in delivering near-capacity quantities of water and was less expensive than 5-inch hose. The hose had the further advantage of a lightweight, waterproof, polymer jacket (commonly referred to as plastic or rubber) that permitted repacking on the fireground, and it had the quick-connect feature of the Storz couplings.

Fire fighters do not have to wash and dry the polymer hose, and the department did not have to buy a dry load of hose to be kept at the station, enabling apparatus to quickly return to service.

Advantages

1. Full pump capacities can be supplied through longer hose lays with less need for relay pumping.
2. Fewer personnel are needed and less time is required to establish highvolume water supplies.
3. Polymer large-diameter hose is lightweight, making it easier to handle when not charged.
4. The polymer hose is more compact than woven jacket hose, allowing more to be loaded.
5. The polymer hose requires little or no maintenance. Hose can usually be reloaded and apparatus returned to service at the fire scene.
6. Polymer hose and Storz couplings require fewer repairs than woven jacket hose and threaded couplings.
7. Storz couplings connect and disconnect quickly.
8. Storz couplings are sexless, eliminating the need for double-male or double-female couplings and eliminating concern over which end of the hose must be connected to what coupling.
9. Polymer large-diameter hose is cost effective.

Disadvantages

1. Storz couplings can disconnect when not locked properly.
2. Large-diameter hose is susceptible to damage when driven over by cars.
3. High volumes of water make large-diameter hose more vulnerable to pressure surges.
4. If a single large-diameter hose line is ruptured, all hydrant water is lost rather than just reduced as in the case of smaller, multiple lines.
5. Lightweight hose with aluminum couplings is more likely to bounce off the back of a hose bed or be caught by the wind, resulting in unplanned hose lays.
6. Conventional hose clamps slip off 4-inch and larger hose. Special hose clamps for large-diameter hose are cumbersome and prohibitively expensive for most departments.
7. Once 4 or 5-inch large-diameter hose is charged it is nearly impossible to move.

By 1979, all of Charlotte’s engine companies carried a split load of 1000 feet of 4-inch hose and 800 feet of 3-inch hose. The 4-inch polymer hose is actually more compact than the 3-inch woven hose, allowing more to be loaded. All ladder companies are also being equipped with large-diameter hose. Biackwelder sees a great advantage in using large-diameter hose with ladder companies having pumps, because these companies can operate independently of engine companies.

In some outlying areas of Charlotte, where the fire department operates quick-dump tankers, large-diameter hose enables quick refilling of tankers and the Storz couplings practically eliminate connect and disconnect time during shuttle operations.

Like any innovation, large-diameter hose has caused some problems. Standard hose clamps do not fit the 4-inch hose, for example. When a hydrant is not in sight of a fire scene, company officers have learned to drop off a walkie-talkie with the fire fighter catching the hydrant. Two blasts on the air horn is a standard signal for the hydrant to be opened. Biackwelder concedes that at large incidents this signal could be confused with air horns on incoming apparatus.

Relief valve connects to the pumper to relieve excess pressure (see diagram in next column).

To more quickly make the hose connection and avoid the possibility of the hydrant being turned on before the connection is completed, apparatus are being equipped with a rear 4-inch intake connection and with a 50-foot roll of 4-inch hose. A fire fighter can break the couplings and quickly connect to the rear intake, using the 50-foot section in cases where otherwise the next 100-foot section of hose would have to be pulled from the hose bed. This procedure can be completed in almost the same time that it takes to clamp a smaller hose.

Charlotte fire companies have also found large-diameter hose vulnerable to damage when run over. Fire trucks can be driven across the hose when necessary, but the undercarriages of cars have ripped it.

To prevent damage, the hose is laid close to the shoulder of the road where it is less likely to be run over. Positioning the hose before it is filled with water is important, because 100 feet of 4-inch hose weighs 540 pounds once it is charged.

Lightweight hose and aluminum couplings have also resulted in unplanned hose lays. On three occasions in Charlotte, the first coupling of the 4-inch line either has bounced off the back of the apparatus or has been caught by wind, causing the entire hose load to be laid. No serious damage has resulted, but the problem has been inconvenient and embarrassing, especially for the engine company that laid 1800 feet of hose while responding on a medical emergency! Recurrence has been prevented by keeping the first hose coupling well under the hose cover and anchoring it with a rubber strap.

Occasionally the Storz couplings have twisted and disconnected. This can be avoided by making sure that the couplings are completely locked.

Large-diameter hose has lower working pressures than smaller hose, typically 400 psi for 4-inch hose and 300 psi for 5-inch hose. The high volume of water moving through large-diameter hose must be shut down smoothly or surging back pressures will cause the hose to burst. Presently, Charlotte does not use relief valves for the large-diameter hose when operating on hydrant pressure. But when relay pumping, relief valves, carried in battalion chiefs’ cars, are used and pump pressures are held below 175 psi. New apparatus are being equipped with inline dump valves.

Clifford Grayson, Charlotte’s chief mechanic, responsible for the maintenance of the large-diameter hose, has only praise for the hose. He notes that the department once had far more trouble with woven hose and threaded couplings than it does now with polymer hose and Storz couplings. Older Storz couplings connected to the hose with wrapped wire were a problem at first, but newer, bolted couplings can literally be replaced on the fireground in five minutes.

To augment the standard 4-inch hose lays, the department still operates the hose tender, which now carries 1200 feet of 5-inch supply line, 900 feet of 3-inch hose, various adapters and a portable hydrant.

Many other North Carolina communities also use hose larger than the traditional 2 1/2-inch size. The Concord, N.C., Fire Department, a 40-person career department, was one of the first in the stale to use 3-inch supply lines, making the switch in 1963. Front-line pumpers carry split loads of 2 1/2 and 3-inch hose. This usually provides the rated pump capacity of 1000 gpm in the business district where hydrant spacing makes supply lines longer than 200 feet a rarity.

Assistant Chief Joe Misenheimer notes that even in outlying areas, looped water mains, no smaller than 8 inches, enable the department to pull intake pressures down to 10 psi through dual 2 1/2 and 3-inch lays while supplying heavy attack lines. However, supplying capacity flows in outlying areas usually requires relay pumping

In 1965, the Guilford College Fire Department. a combination career/volunteer department, started using 3-inch supply lines. In its industrial area, two engines and a Telesqurt, each equipped with 1000-gpm pumps, carry split 1200-foot loads of 3-inch hose. Another 750-gpm engine, in a rural portion of the fire district, carries a continuous 1000-foot load of 3-irtch hose.

The department, under the direction of Fire Chief Bob Wilson, has developed tour tactical water supply operations. Two involve quick-dump tanker operations and two use 3-inch hose with hydrants. High-volume operations call for the first engine to lay dual 3-inch lines from the hydrant and for the second engine to take suction on the steamer connection and to relay pump In this manner, 1000 gpm can be delivered 600 teet from the hydrant.

Wilson recalls a fire incident at an apartment building where 3-inch hose made a difference. The first-due engine attacked with a preconnected 2 1/2-inch line but could not darken fire rolling out the front of the vacant building. The second-due Telesqurt laid dual 3-inch lines and set up in front of the building while the 2 1/2 -inch hand line held the fire. There were only eight fire department personnel on the scene. Moreover, Wilson was in a back brace, the assistant chief was recovering from an eye injury, and a pump operator was on crutches. Bystanders laid odds that this crew was not going to extinguish the fire, but 1000 gpm was easily established through the dual 3-inch lines attached to the Telesqurt which knocked the fire down in a matter of seconds, leaving hot spots to be mopped up with a 1 1/2 -inch line.

The Shelby. N.C., Fire Department, once famous for its innovative reverse lay hose trays, has equipped its 1250-gpm engines with 1200 feet of 5-inch hose. Although it has had some trouble with a 5-inch inline dump valve not seating properly and with stiff hose couplings, Assistant Chiet Levon Kennedy says the department is quite satisfied with the large-diameter hose. Presently, Shelby is experimenting with polymer attack lines and is investigating the possibility of purchasing a portable hydrant. Because some hydrants in Shelby have no steamer connections, pumpers carry 2 1/2 X 5-inch Siamese connections with short sections of 3-inch hose for hooking to the 2 1/2-inch hydrant outlets.

Assistant Chief Ted Beshears of the Flickory, N.C., Fire Department reports that 1000 teet ot 5-inch hose is loaded on one ot the department s engine companies that answers alarms in outlying areas of the city, where hydrant spacing is infrequent. The department is using a portable hydrant and plans to convert its other engines to 5-inch supply line. In addition, the department is looking into the use of 1 3/4-inch attack lines as a result of the added water supply available with the large-diameter hose. Hickory has also experienced problems with couplings disconnecting when they were not fully locked.

Large-diameter hose is not used only in urban areas. It has just as much application in suburban and rural communities where hydrants are sparse or where lakes and ponds serve as water sources.

The Pinoca Volunteer Fire Department operates a 750, a 1000 and a 1500-gpm pumper in a mixed residential, industrial and rural community. These pumpers carry 2 1/2 and 3-inch supply lines but are backed up by a utility truck that can lay 1000 feet of 5-inch hose from a reel mounted on the rear of the truck Pinoca s Deputy Chief David Black feels that mounting the hose on a reel is not a necessity, but points out that the electrically operated reel makes picking up the hose quick and relatively easy. The 1000-gpm pumper is equipped with a 50-inch discharge outlet fed by three 2 1/2-inch pipes off the pump’s discharge manifold. Pinoca also uses a relief valve and portable hydrant. Black notes that the only problem with the large-diameter hose has occurred when a section burst due to water hammer when a valve was closed too quickly.

Six engine companies of the WinstonSalem Fire Department now operate with a 4-inch supply line. Two companies in the downtown area, where hydrants are plentiful, carry 500-foot loads and the others are equipped with 1000-toot loads. Two and three-person engine companies are supplemented by public safety officers responding in patrol cars. Even in a worst-case response scenario, high-volume water supplies can be established easily by a pump operator and a tire tighter

Battalion Chiet Steve Baldwin sees the large diameter hose as a definite benefit and points out that using 2 1/2-inch supply lines is a waste of pump capabilities. Winston-Salem apparatus is currently being retrofitted with 4-inch Storz intake and discharge connections and with inline dump valves. The department is also considering a switch to 1 3/4-inch attack lines. Like Charlotte, Winston-Salem engines carry a 50-foot roll of 4-inch hose to add onto a supply line without pulling an extra 100-foot section off the hose bed. There have been similar problems in Winston-Salem with the Storz couplings coming apart when they were not properly locked together.

photos by the author

Another public safety department in Durham, N.C., has equipped most of its pumpers with 600-foot loads of 5-inch hose. A warehouse fire was contained with the help of large-diameter hose, which enabled companies to quickly establish water supplies and pump into master streams at full capacity.

Under the direction of Fire Chief )oe Letzing, Durham has established a hydrant procedure in which a short piece of rope tied to the first length of hose is looped over the fire hydrant, keeping the fire fighter at the hydrant clear of the hose as it is laid from the hose bed. A fatal accident occurred in that city five years ago when a 2 1/2 -inch supply line coupling snagged in a hose bed, throwing the public safety officer at the hydrant onto the pavement. Letzing sees the rope procedure as especially useful with large-diameter hose.

Fire Chief John Love of the Burlington, N.C., Fire Department has equipped each engine with 500 feet of 5-inch supply line. With seven years experience using largediameter hose, Love is pleased with its performance, noting only a few problems with tight couplings and with abrasion to the hose. At a lumberyard fire, using 250 feet of 5-inch hose one engine simultaneously pumped a 1 ¾ -inch tip on an aerial and supplied two 2 1/2 -inch hand lines.

Cost of hose must certainly be considered. Large-diameter hose is more expensive than smaller hose; 4-inch polymer hose is about 21/2 times more expensive than 2 1/2-inch woven jacket hose. But several factors offset the cost. One is the eliminated dry load of hose at the station, another is lower maintenance costs. Most significant, however, is the elimination of the need for multiple parallel supply lines at the fire scene.

The disadvantages of larger diameter hose have not dissuaded departments from using it. In Charlotte, for example, 4-inch hose is not only well accepted, it is leading to other innovations. Two-inch polymer jacket attack lines have been tested over the past two years. Because the hose has held up well and can be repacked without washing or drying, and because the 4-inch supply lines provide ample water, plans now call for phasing in 2-inch attack lines using midrange nozzles (100 to 300 gpm), with the elimination of booster and 1 1/2 -inch lines on all new apparatus. The polymer jacket makes the 2-inch hose as easy to maintain as booster line while providing a much greater flow. The 2-inch hose is nearly as maneuverable as a 1 1/2-inch line and will provide a flow almost equivalent to a 2 1/2 -inch line.

Departments that use large-diameter hose have increased the efficiency of their operations in terms of water delivery and use of personnel. They also tend to make quick fire stops. It is well established that a properly orchestrated, high-volume attack on a structure fire not only provides a safety margin should conditions worsen, but also results in less water damage. Even at routine alarms it is better to have more than an adequate amount of water available than for the fire to overcome water supplies. In summing up the effectiveness of large-diameter supply lines, Charlotte’s Assistant Chief Wilson says, “Everything dries out. Nothing unburns.”