By Paul Shapiro
Battling a working fire requires many coordinated tasks to be successful. One of the most important parts of the overall strategy that has the potential to make or break an operation is being able to obtain adequate water delivery. Notice that I said water delivery instead of water supply. Water supply implies that we are interested only in finding the water. Obviously, that is half the battle, but what about getting the wet stuff on the red stuff? Isn’t that really the overall goal?
Producing adequate firefighting streams at large fires can be a complex operation involving the efforts of several people, numerous pieces of equipment, and hundreds (sometimes thousands) of feet of fire hose. Needless to say, there needs to be an operational plan to make all of this happen. In fact, a major water delivery operation is almost worthy of its own command structure.
To avoid freelancing and to provide for a structured water delivery operation, there needs to be a person in charge of the overall fireground water-delivery system–thus the position of water management officer (WMO).
The duties of the WMO are simple and yet require the knowledge of several areas of water movement on the fireground. The WMO’s sole responsibility is to manage the water delivery on the fireground at its present state as well as a possible escalation of the water-delivery demands.
Let’s take a look at some of the areas the WMO needs to be aware of. They can be divided into two categories: water supply and water discharge.
As mentioned earlier, the WMO needs to ensure that there is an adequate water supply to the fireground for the present stage of the fire as well as for a possible escalation. There are several things that the WMO should be aware of to assist in maintaining the water supply.
The WMO should note the static pressure of the hydrant system being used. The static pressure of a hydrant system is half of what one needs to know to determine how strong a hydrant system really is. Obviously, the higher static pressure will potentially be able to move water through supply hose further. The other half of what needs to be known is the volume of water that is available from the main itself. A high static pressure on a low-volume water main will usually not produce the big water. A good example of this is a hydrant system I have used that has a 150-pound per square inch (psi) static pressure but is supplied by a three-inch water main. As soon as this hydrant is opened, the residual pressure drops down to almost nothing, flowing only 400 gallons per minute (gpm). On the other hand, I have seen a hydrant system with a 65-psi static pressure and, after flowing 3,000 gpm, the residual pressure was still at 45 psi.
The WMO should also note the residual pressures of the pumpers working at the fire. A low residual pressure is an indication of low incoming water to that unit. When small-diameter hose (2½-inch and 3-inch) is used for the supply line, a low residual pressure that needs immediate attention is about 20 psi. On the other hand, if large-diameter hose (LDH) is being used, especially 5-inch, the residual pressure can usually be brought down to zero in situations where water is lacking. This is not to say that a low residual pump intake pressure with the use of LDH is acceptable or should not be addressed.
It is important to realize that a low pump intake residual pressure indicates a low water volume at the pump but not necessarily at the hydrant. Often times, the supply line itself is the restricting factor in obtaining more water to the pump. LDH offers the best vessel for delivering maximum flow.
(1) A low intake pressure at the pump panel indicates a low volume at the pump but not always at the hydrant.
To obtain maximum flow to a single engine company from a hydrant system, consider multiple supply lines from one or more hydrants alone or in conjunction with a relay-pump operation. If a relay-pump operation is being considered, make sure that there is a sufficient number of pumpers and enough hose to deliver the required volume of water from potentially long hoselays.
(2) These single-engine company operations initially received water from a hydrant and have depleted their water supplies. The units were in a good position and had the means to flow more; they just needed more water. Additional supply lines were set up in relay-pump operations to supplement the engines’ water supplies.
Occasionally at fires that demand large flows, the initial responding pumpers will bring in supply lines from the closest hydrants. As the incident and the water flow requirements escalate, there is a good chance that the first-in units could start exhausting their initially established supply lines. These units are usually in a good spot to deliver the water in the fire attack and have the ability to produce more fire streams; they just need more water.
Individual relay pump operations can be set up to supplement multiple pumpers at the fire using dual-pump and/or manifold operations. It is important to know how many intakes each pumper has as well as their compatibility to specific sizes of hose. This will help determine the type and amount of supply line operations that need to be established.
(3) A relay-pump operation supplying two engines with the help of a dual-pump operation.
(4) A relay-pump operation feeding into a 5-inch gated manifold, which is in turn supplying two engines.
(5) A dual 5-inch relay works well when the hydrant has enough water.
These types of water-supply operations can take several minutes to set up. Do not wait until a water-supply problem happens. If the water supply is dwindling and the fire is not subsiding, initiate the appropriate supply-line evolutions needed to bolster the water supply.
Have access to water supply maps. These maps should include hydrant locations, main sizes, and locations, as well as potential static water sources.
Be aware of specific water-supply problems associated with the operation, such as low-pressure/low-volume hydrants, lack of hydrants, dead-end mains, etc.
Be aware of all potential mutual-aid companies and their equipment as it pertains to establishing water supplies. Make sure that compatibility among agencies exists.
The WMO should have a thorough understanding of the municipal water system in all areas that are served by the fire department. There should also be a good working relationship with the water department, especially during a major fire when the water requirements of the system may have to be boosted.
Getting water to the pump is only half the battle. It is equally important to be able to discharge the water onto the fire by means of an adequate fire stream. Let’s see what it takes to produce this result.
Be aware of the discharge capabilities of all the units involved in the operation. If more water is requested from a pumper already discharging and the water supply is sufficient, decide whether or not it is capable of moving more water. There are several indicators that will help determine how much more water, if any, will be available. Centrifugal pumps have the ability to deliver much more than what they are rated at when supplied by a positive-pressure water source, i.e., a hydrant system. In fact, in some cases, the capacity can be doubled.
Knowing the rated pump capacity as well as the current flow will give you an idea of what might be available from a pumper. As a rule of thumb, as long as the water supply is adequate, expect at least 800 to 1,000 gpm above the rated pump capacity.
Check the revolutions per minute (rpm) of all pumpers involved with the operation. During high-flow operations, the engine of the apparatus involved with the operation will often be working at higher rpm. A check of the unit’s tachometer will help make the determination on whether or not more water can be produced. If the rpm are creeping up to the governed speed of the engine, more water may not be available.
Sometimes the hand throttle on the pump panel will limit the amount of additional water available from a pump. At high-flow operations, the hand throttle on the pump panel can be turned out to a point where mechanically it will not turn anymore.
The WMO should evaluate discharge evolutions involving the hoselay itself and the actual nozzle and make corrections as needed. If the wrong size hose is being used, the friction loss may be too high to deliver the required flow. The wrong size tip on a smooth bore master stream operation may also interfere with the proper water requirements, as well as produce an inferior stream.
(6) The WMO is responsible for making the streams count.
Fireground Water Management Checklist
- Static pressure of the hydrant system
- Residual pressures of the pumpers involved in the operation
- Hose size of supply lines
- Quantity and sizes of intakes on the pumpers involved in the operation
- Water supply maps
- Specific water supply problems
- Possible need for a relay pump operation
- Mutual-aid companies and their compatibility to the operation
- Approximate flows from the pumpers involved in the operation
- Pumper discharge capabilities
- Rpm of the pumpers involved in the operation
- Discharge evolutions on the fireground
The end result of any fireground large-flow water delivery operation is to provide the required volume of water in the form of effective fire streams to reach and overwhelm the British thermal units of the fire and achieve a knockdown as quickly as possible. To do this as efficiently as possible, it is important for the WMO to thoroughly understand and implement as many aspects of a large-flow water delivery operation as possible. The WMO position in the command structure of a fire cannot be ignored or taken lightly.
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.