By Paul Shapiro
Often, incident commanders (ICs) and company officers (COs) are required to make decisions on the fireground that may involve the movement of water through fire department hose evolutions. To make the correct decision, these personnel must have a good understanding of fireground water movement, including knowledge of hydrant systems and hose, pumper, and nozzle capabilities, or they may order water movements that may not be possible.
“Did You Know?” is a collection of facts about the movement of water on the fireground by fire department pumping apparatus. This information is designed to help ICs and COs better understand the movement of water and, consequently, enhance their decision-making capabilities on the fireground.
1. A pumper can deliver up to two times its rated capacity when hooked to a strong water supply hydrant system. Don’t be confused by the pump’s rated capacity. Pumps are rated at draft. To obtain the most from your pump, you must address the following points:
- A good hydrant system, both in pressure and in volume
- Large-diameter hose (5-inch works best)
- Dual supply lines
- Low engine pressures and engine revolutions per minute, which are accomplished through large-diameter discharge plumbing and large-diameter hose discharge lines.
2. The 2 1/2-inch gated inlet on the pump can supply only a maximum of approximately 300 to 800 gallons per minute (gpm), depending on the strength of the hydrant system or the incoming pressure from another engine and the size of the supply hose. These intakes are designed for tank refill.
3. A single supply line can be used by more than one pumper by connecting intake to intake with supply hose. This is known as dual pumping. This operation allows hydrant pressure to move the unused water from the first pumper to the second pumper through the dual-pump supply line.
4. The static pressure of a hydrant indicates only part of the water potential of the hydrant itself. The water main feeding the hydrant must also be capable of supplying the water volume. All the pressure really does is move the water out of the hydrant.
5. The 2 1/2-inch port on the hydrant can supply approximately 80 percent of what the large hydrant port can supply when using large-diameter hose.
6. A single 5-inch supply line connected to the large hydrant port will not be able to supply the capacity of the pump in some cases.
7. Laying a second 5-inch supply line from the 2 1/2-inch on the same hydrant or from the large port from a second hydrant will increase the flow to the pumper significantly.
8. A 100-foot section of 5-inch hose weighs 110 pounds empty–remember this when making the decision on whether to lay a supply line or have the poor operator hand-stretch it.
9. A single 2 1/2-inch side discharge can deliver 1,000 gpm efficiently. In fact, if used in a relay pump operation, the 2 1/2-inch discharge can flow up to about 1,800 gpm. When choosing the proper discharge, consider that the least number of restrictions in the plumbing will provide the best results.
10. A 4-inch discharge provides the most efficient means for discharging big water. Flows in excess of 2,000 gpm can be achieved efficiently as long as the water is available from the water source.
11. A single 2 1/2-inch discharge line can supply a portable monitor with 800 gpm from 200 feet away and 500 gpm from 300 feet away.
12. The 5-inch by 2 1/2-inch three-way gated manifold with pressure relief can regulate the proper pressures of up to six handlines without the engineer’s assistance.
13. The inline foam eductor is capable of moving the proper percentage of foam 150 feet with 1 1/2- hose, 300 feet with 1 3/4-inch hose, and 2,700 feet with 2 1/2-inch hose.
14. In a building fire protection system supplied directly from water main pressure, or indirectly from the water main using the building fire pump, the fire department pumper does not assist–or should I say add–to whatever is being delivered. Because of clapper valves designed in the system, either the water main/building fire pump provides the system or the fire department pumper. The fire department pumper is connected to the system as a backup in case the water main/building fire pump fails or falls short of providing the required amount of water. For the fire department pumper to provide water into the system, the engine pressure must exceed the system pressure.
15. It is possible for a fire department pumper engine’s pressure to exceed 300 pounds per square inch (psi) when pumping into the fire department connection in a high-rise building.
16. The pump, all discharge plumbing, and valves on an engine company are all capable of operating pressures from 500 to 600 psi.
17. A smooth bore tip on a monitor can be pumped higher than the recommended 80 psi nozzle pressure. The limitations on the maximum allowed pressures are as follows:
- Do not exceed the maximum allowed inlet pressure of the appliance.
- Do not exceed the rated flow of the appliance.
- Do not exceed the maximum allowed nozzle reaction of the appliance. A 1,250-gpm appliance has a maximum allowed nozzle reaction of 631 pounds (lbs.). A 2,000-gpm appliance has a maximum allowed nozzle reaction of 1,010 lbs.
18. A 2 1/2-inch handline can flow 500 gpm using two firefighters with a 1 1/4-. 1 3/8- or 1 1/1-inch tip or a 500-gpm fog nozzle.
19. A 1 3/4-inch handline can flow up to 325 gpm using one firefighter with a 1 1/4-inch smooth bore tip or a fog nozzle.
20. A 2-inch handline can flow up to 400 gpm using two firefighters with high- pressure hose and a 1 1/2-inch tip at 50 psi NP.
21. A 500-gpm blitz attack can be achieved from a 500-gallon booster tank successfully.
22. Fire hose can have more friction loss with a subsequent flow loss when laid out with bends in it vs. when in a straight line. Keep in mind that a discharge hose evolution will have bends in it 99 percent of the time.
Paul Shapiro is director of Fire Flow Technology. He is a nationally recognized instructor on large-flow water delivery. He is also a retired engineer from the City of Las Vegas (NV) Fire Department. He has authored numerous articles for fire trade magazines. He has been in the fire service since 1981 and is author of Layin’ the Big Lines and produced the first in a series of videos on large-flow water delivery. He is available to answer questions; he can be reached at (702) 293-5150 or Layinline @aol.com.