For departments that have to use ponds, streams or other alternative water supplies, moving water to the scene of a fire has become a problem with many solutions. Most of these solutions involve a mix of tactics, personnel, apparatus and equipment to maximize the flow rate under a variety of conditions.

But simply moving water from one point to another isn't enough to establish a water supply. To gain full credit from the Insurance Services Office, departments have to meet certain requirements. In many cases, these requirements will determine method of moving water, as well as the sequence of operations needed to make everything work properly.

ISO requires that the first-responding unit must start flowing water within five minutes of arrival. The minimum flow rate for a Class 8 ISO classification is 250gpm. The department then has 10 minutes to increase the flow rate if it wants a higher classification. The required flow rate is determined by the size and construction of the fire structure, the distance from other structures, and several other factors. Once the water starts flowing, the department must maintain a steady flow rate for two hours.

Given these requirements, many departments have found that large-diameter hose relays are a more efficient way to move water for distances up to about 2,500 feet, while tanker shuttles are more efficient for distances more than 5,000 feet. For distances in between, either method can work well.

Tanker types and sizes

Most rural departments rely on tanker shuttles because of the greater distances involved. In these cases, departments need to determine the types and sizes of tankers to best meet the ISO requirements and give them the most efficient water supply. Each has its own advantages and disadvantages.

Large pumper/tankers carry a full complement of engine company equipment and usually have a water tank capacity of 1,500 gallons or more. They are useful as first-responding units where the number of personnel is limited or where the supporting tankers will be delayed. In these cases, a minimum crew can easily start flowing water from the tank within the allowable time and can maintain the minimum required flow for six to eight minutes, depending on the tank size. This buys time for additional personnel and apparatus to arrive and set up. Having all the attack hose, monitors, ground ladders and other equipment of an engine also makes the attack more effective and can give the department credit for an engine company. Some of the disadvantages of this type of apparatus are the cost and size compared with a straight engine or tanker.

Attack tankers equipped with pumps offer some of the same advantages as pumper/tankers, but they lack the full supply of engine company equipment. When these tankers respond with an engine, they can start supplying water with a minimum crew and then later break away and join the tanker shuttle. They also can be used to refill smaller pumpers or to attack wildfires. Many tankers now are being specified with pumps to give them this added versatility. One of the disadvantages is that these units need to respond with a structure pumper to get full ISO engine company credit.

Straight tankers are popular in departments where multiple units are needed because the required flow rate is high or the distances to a water source are long. When maneuverability isn't an issue and an adequate fill rate is possible, tankers up to 3,500-gallon capacity can provide higher sustained flow rates. For many departments, however, 2,000-gallon tankers offer an ideal combination of capacity, cost and maneuverability. To maximize efficiency and minimize shuttle time, departments often specify large fill and dump ports. Multiple dump ports on the rear and sides of the vehicle add flexibility and can improve safety by eliminating the need to back up to a drop tank. The disadvantage of this design is that it only can be used to shuttle water and has no attack or pump off-load capabilities.

Vacuum tankers have the added advantages of being able to self-load and provide access to water sources that might be difficult to reach. Some vacuum tankers can load their own water at rates in excess of 1,000gpm, and they can draft through 40 feet or more of lightweight suction hose from vertical lifts up to 28 feet. At the dump site, they can reverse the vacuum pump to pressurize the tank and speed off-loading. One disadvantage of this configuration is its higher costs, which can be offset if a department is able to eliminate a pumper at the fill site.

Importance of drop tanks

Both tanker shuttles and hose relays require drop tanks at or near the fire scene to hold the arriving water and provide a drafting point for one or more pumpers. Most tankers carry their own drop tanks, which are sized to accommodate a full tank load, plus a little extra. Multiple tanks can be connected through siphon tubes or hoses, or by interconnecting the drain sleeves. Some departments use long, rectangular tanks or line up the tanks end to end to allow easy access along narrow roads. Others position the tanks in a diamond pattern, corner to corner, to allow room for personnel to place the siphon hoses.

The older, frame-style tanks offer sturdy sides and provide protection for the tank liners, but they have to be carried flat along the length of the tanker and are relatively heavy. Because of their size and weight, they take two or more people to set up. The newer, frameless-style tanks with flotation collars can be rolled for compact storage and are significantly lighter, but they are only available in round shapes and have smaller top openings that may require dump chute extensions. One or two people can usually set them up. Again, departments should choose the shape and size that best suit them.