ADVANCED PUMPING SKILLS TANDEM AND DUAL PUMPING
BY LEIGH T. HOLLINS
Operating a pumper involves various levels of skills: simple skills such as knowing how to pump a booster line, intermediate skills such as flowing multiple lines, and advanced skills such as using residual hydrant pressure to determine water availability. Tandem pumping and dual pumping are advanced skills that have as prerequisites a thorough understanding of basic and intermediate skills.
Some confusion appears to surround the techniques of tandem and dual pumping. Some textbooks say they are the same. Others give the definition of one of these terms for the other, and some books describe each as they will be described in this article. To clear up the confusion, compare the simplest definitions of the two terms. Dual means “double,” and tandem means “one after another.” These short definitions are aids in matching the proper name with the proper technique.
TANDEM PUMPING
Tandem pumping, a short pumper-to-pumper relay (one after another), is used to overcome pressure loss due to elevation. This technique can produce pressures higher than normally would be possible with a single pumper while maintaining water volume. If, for example, 100 pounds per square inch (psi) is the pressure required to supply standpipe hoselines on the 40th floor of a high-rise building, the pump operator will have to produce 300 psi at the fire department connection due to the high pressure required to overcome elevation (200 psi–rough rule of 5 psi per floor ¥ 40 floors). If a large volume of water is also required, tandem pumping is the only way a pumper can supply it. To completely understand this technique, pump operators must be familiar with the rated capacity of a fire pumper (see Chart 1 below).
As shown, a pumper rated at 1,000 gpm can produce 50 percent of its “rated capacity” (500 gpm) at 250 psi, 70 percent (700 gpm) at 200 psi, and 100 percent (1,000 gpm) at 150 psi. The test to determine the rated capacity of a pump is performed while the pump is drafting water from a static source. If a pumper is receiving water under pressure, such as from a hydrant or another pumper, the maximum discharge pressure can increase proportionately to the pressure being received (intake pressure). The pressure actually being produced by the pump is known as “net pump pressure.”
Chart 2 refers to a pumper rated at 1,000 gpm receiving 50 psi from a hydrant. It now can produce 50 percent of its rated capacity (500 gpm) at 300 psi, 70 percent (700 gpm) at 250 psi, and 100 percent (1,000 gpm) at 200 psi. The pressure advantage realized while receiving water under pressure is obvious.
EXAMPLE
The following example illustrates how intake pressure and net pump pressure work to a pump operator`s advantage. It may seem confusing at first, but keep in mind that the basic definition of tandem is “one after another.” Pumper B (one) is pumping after pumper A (another). Also refer to Chart 3, which shows the additional pressure advantage obtained by tandem pumping.
Pumper A is receiving water from a 50-psi hydrant. Pumper B is 100 feet away and connected to a fire department connection. Pumper A is pumping 100 percent of its rated capacity at 150 psi net pump pressure plus the 50 psi intake pressure to pumper B. Therefore, pumper B`s intake pressure is 200 psi. If pumper B provides 100 percent of its rated capacity at 150 psi net pump pressure, plus the 200 psi intake pressure, the resulting maximum discharge pressure will be 350 psi (as shown in Chart 3). (Pumper B alone would be able to produce only 200 psi maximum discharge pressure from a 50-psi hydrant if it were delivering 100 percent of its rated capacity.) Tandem pumping produces greater pressures while still maintaining water volume.
When tandem pumping, do not exceed annual service test hose pressures, and take the following precautions to reduce the risk of damage and injury:
Keep all personnel and civilians away from hoselines.
Lash lines together at each end and at couplings, or lash to a substantial object.
Use multiple smaller lines instead of one large-diameter hose (LDH).
Use threaded couplings instead of the quick-connect or one-third turn type.
Always shut down at the water supply first.
DUAL PUMPING
Dual pumping is using a single hydrant to supply two pumpers. The residual pressure available at the first pumper`s unused intake is used to supply a second pumper (double pumping). This technique uses available water more efficiently, provides shorter hoselays, and requires less equipment. The result is a quicker, safer, and less labor-intensive water supply operation. The basis for this technique lies in the question, Why lay hoselines to another hydrant if the same volume of water is available at the unused intake of the first pumper?
Understanding dual pumping is contingent on the pump operator`s having a complete understanding of how residual pressure determines total water availability and rated capacities (discussed above) because the first factor to be considered for dual pumping is whether enough water is available for the technique to work efficiently. When a pumper is hooked up to a hydrant, the static pressure (the intake pressure prior to flowing any water) must be recorded. When water begins flowing, the intake pressure drops. The remaining pressure is the residual pressure. This drop in pressure can be used to determine the remaining amount of water available from the hydrant. If it is determined that enough water is available to supply a second pumper`s needs, dual pumping may be the best choice. To determine whether dual pumping is the best choice, consider the following factors:
Do the gpms needed to extinguish the fire exceed the single pumper`s capacity?
Is the single hydrant capable of supplying the required gpms?
Is a second pumper available?
Is the secondary hydrant on the same water main?
Is placing the second pumper near the first pumper acceptable?
If the answer to all five of these questions is yes, dual pumping is probably the best choice.
Advantages of Dual Pumping
The advantages of dual pumping include the following:
Water is used more efficiently.
The closer grouping of resources facilitates coordination among companies.
The need to lay a hoseline to a secondary hydrant is eliminated.
Placing attack hoselines in service is expedited.
No additional equipment is required.
The objective can be achieved with minimal staffing.
The second pumper remains on-site for equipment use.
There are no additional supply lines to impede area traffic or incoming companies.
The placing of companies back in service is expedited.
Although dual pumping is not a difficult procedure to learn, it must be practiced before pump operators can perform it efficiently. Certain equipment, such as large gated intakes on one or both sides of pumpers and soft-suction hose, can make the procedure easier, although dual pumping can be accomplished without them.
Basic Scenarios
There are three basic dual-pumping scenarios:
Large gated intakes are available on both intakes of each pumper:
1. Pumper A connects to a hydrant using large suction hose.
2. Pumper A pumps the lines required.
3. Pumper B positions near Pumper A (distance depends on the length of the hose to be used between A and B).
4. Pumper B connects its large suction hose to its large gated intake.
5. Pumper B connects the other end of its large suction hose to Pumper A`s unused large gated intake.
6. Both pumpers open their large gated intake valves.
7. Pumper B is now receiving Pumper A`s residual pressure.
8. As Pumper B opens its discharge gates to supply hoselines, Pumper A throttles up to maintain proper discharge pressures.
9. Both pumpers now are operating off one hydrant, dual (double) pumping.
Large gated intakes are available only on one intake of each pumper:
1. Pumper A connects to a hydrant using large suction hose to its large gated intake.
2. Pumper A pumps the lines required.
3. Pumper B positions near Pumper A (distance depends on the length of the hose to be used between A and B).
4. Pumper B connects its large suctions hose to its large gated intake.
5. Pumper A slowly gates down its large gated intake until the residual pressure is near zero while throttling up to maintain discharge pressures.
6. Pumper B connects the other end of its large suction hose to Pumper A`s unused large suction intake.
7. Both pumpers open their large gated intake valves.
8. Pumper B now is receiving Pumper A`s residual pressure.
9. As Pumper B opens discharge gates to supply hoselines, Pumper A throttles up to maintain proper discharge pressures.
10. Both pumpers now are operating off one hydrant, dual (double) pumping.
Large gated intakes are not available:
1. Pumper A connects to a hydrant using large suction hose.
2. Pumper A pumps the lines required.
3. Pumper B positions near Pumper A (distance depends on the length of the hose to be used between A and B).
4. Pumper B connects its large suction hose to its large suction intake.
5. The hydrant is slowly turned down until Pumper A`s residual pressure is near zero while throttling up to maintain discharge pressures.
6. Pumper B connects the other end of its large suction hose to Pumper A`s unused large suction intake.
7. The hydrant is slowly opened.
8. Pumper B now is receiving Pumper A`s residual pressure.
9. As Pumper B opens discharge gates to supply hoselines, Pumper A throttles up to maintain proper discharge pressures.
10. Both pumpers now are operating off one hydrant, dual (double) pumping.
As dual pumping is practiced, operators will discover that the technique may be adapted to better fit the needs of their equipment. During preplanning activities, personnel may discover that certain buildings or facilities in their response area can be identified as potential dual-pumping “targets,” meaning that dual pumping would be the best choice should large quantities of water be required for a fire at the site.
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Many methods allow us to “fight fire with water.” Some let us apply water to the seat of a fire from a booster tank; some require that we draw water from lakes, streams, or ponds; and others involve our using hydrants that supply our pumpers with water under pressure. Knowing the various methods, practicing them, and employing creativity will increase our options for fighting fire with water. Tandem and dual pumping are two such options. When everyone involved with a water-supply operation understands these two advanced pumping procedures, their advantages, and when and how to use them, they can be two more weapons in our “strategic and tactical toolbox.”
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(Left) Pumper A pumps 200 psi to Pumper B. (Right) Pumper B receives 200 psi, then pumps a total of 350 psi to the fire department connection. (Photos by author.)
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(Left) Pumper B. Note the lashed, secured discharge lines. (Right) Multiple smaller lines are used to supply the fire department connection. This makes the operation safer: If a line should burst, the water supply to the firefighters will not be interrupted.
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(Above left) Large gated intake valves allow for easier water supply operations. (Above right) Pumper B (right) positions next to Pumper A for the intake-to-intake connection. (Below left) A completed intake-to-intake connection. (Below right) Dual pumping in operation.
LEIGH T. HOLLINS, a member of the fire service since 1976, is training director for the Southern Manatee and Cedar Hammock Fire Departments in Bradenton, Florida, where he previously served as lieutenant and captain, and director of Starfire Training Systems, Inc., in Manatee County, Florida. He is a Florida-state certified EMT, fire officer instructor, and fire inspector instructor.
