By Brian Brush
Though not true in all cases, there is an unfortunate trend that has developed across a wide swath of the American fire service: the critical function of water supply is lacking critical thinking. Improvements in municipal water supply and changing to large diameter hose and multi-purpose apparatus without organizational adjustment may lead to unintended operational limitations. If your department is primarily a forward lay department (hydrant to fire scene) and primarily a single-line supply (steamer outlet to eye of the pump), I would recommend you take a few minutes to consider how you got to that point, how flexible you are working outside of that operation, and if you are meeting the potential of your source.
A good first step is to get out and see what you are working with. A standard hydrant flow test measures the rated capacity of a fire hydrant at 20 pounds per square inch (psi). This may require the removal of the steamer and one or both of the side discharges to drop the hydrant residual down as near to 20 psi as possible. The rated capacity calculation can easily be found online or in your city’s water or fire prevention department. I am fortunate to work in a city that is 98-percent hydranted with nearly all of them supporting flows of 1,500 gallons per minute (gpm) or greater. In the city core, hydrant capacity exceeding 2,500 gpm is common. This is the type of foundational information that allows you to dive into an evaluation of true operational potential.
RELATED FIREFIGHTER TRAINING
To simplify discussion, here are some ballpark numbers for water supply potential. Given a single source as a municipal hydrant supply (60-80 psi at the steamer) with a municipal forward lay, single line 300-500 feet.
1 x 3-inch hose 500 gpm
1 x 4-inch hose 1,000 gpm
1 x 5-inch hose 1,500 gpm
1 x 6-inch hose 2,000 gpm
To put these numbers into context, we will use National Fire Protection Association (NFPA) 1710, Standard for the Organization and Deployment of Fire Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by Career Fire Departments, as our guidance. NFPA 1710 sets the minimum recommended water supply for a 2,000-square-foot, single-family dwelling at 400 gpm. The 400 gpm water supply minimum is built from the NFPA 1710 fire attack recommendation of two hoselines in place (attack and backup) with a combined flow of a minimum of 300 gpm. When these numbers are linked to the supply options, they all meet the fireground standard and provide for varying reserve capacity.
Our department uses four-inch as our primary supply line. Using the numbers presented, 1,000 gpm to the scene through a single line forward lay greatly exceeds the NFPA 1710 recommendation for the single-family dwelling fire. It also exceeds the 500-gpm NFPA 1710 recommendation for a strip mall or apartment fire response where additional exposure lines may be deployed.
If the goal is to meet an NFPA recommendation, any of the single supply line selections above accomplish the mission and the discussion is over. If the operational goal is to prepare for the full potential of incidents and to maximize the full potential of the department, we need to determine if a gap in potential exists and find out if it is within our control.
For many agencies the water supply system is the limitation, but in others, the limitation is fire department operations. Our city has a strong water supply infrastructure, with most of our hydrants supporting an average of 1,800-2,000 gpm. By accessing this system with a single four-inch supply line in a forward lay operation we are only using about half the available water. If there is a fire flow demand at the fire of more than 1,000 gpm and there is more than 1,000 gpm available at the hydrant, the fire department operation is the limitation.
The same can be said for many of the quint apparatus in service today across the country. Quint apparatus will have hose, a pump, and water to support fire attack operations as well as an aerial waterway. Often due to the aerial waterway, a quint is spec’d with a larger volume pump of 1,500-2,000 gpm. This spec is to support the fire flow of the aerial master stream and the potential combination of defensive lines also operating off the apparatus. Even when this apparatus is set up with five-inch supply hose, if the standard operating procedure is a forward lay of a single line from an unsupported hydrant, the restriction in potential is the fire department. The hydrant may provide more water and the apparatus can support operations exceeding 1,500 gpm, but the limitation is the single unsupported supply line. If the department also has policy of not operating a pump below a certain residual pressure, it is likely that, given a moderate distance forward lay of a single five-inch supply line, flows may be limited to 1,300 gpm. This limitation is not by the pump or the water department, but by equipment selection, operation, and policies of the fire department.
Revisiting the Reverse Lay
Before we move into opportunities for improving forward lays, let’s revisit the reverse supply lay. This reverse supply lay involves the second-due apparatus laying from the attack pumper at the fire to the hydrant. This operation is common in urban areas where apparatus arrive in short order.
Benefits of this method include the fact that it gets boots on the fireground quicker, as the officer and firefighter are dropped at the scene and the driver secures the water supply at the hydrant. In tighter areas, where access is at a premium, moving the second engine away from the scene provides access for the truck company. Finally, placing a pump at the hydrant makes supply to the attack pumper dynamic, increasing volume potential, and it places in a full tank in the system as a safety factor.
The reverse supply lay has drifted out of preference in many organizations for a number of reasons, most commonly the pure habit and routine of dropping a firefighter at a hydrant and bringing water to the scene. Another common reason is in the areas where the response distances won’t allow for the first-arriving apparatus to defer water supply to a later-arriving unit. Finally, in some organizations it has become policy that the first-arriving apparatus secures their own water supply. With all that said, beyond the use as initial fireground supply, a reverse supply lay may also be used to secure a secondary supply for the attack pumper.
Flexibility at the Hydrant
When it comes to making water supply improvements for fire department operations, the low hanging fruit is at the hydrant. Hydrant manifolds like the three-way valve shown (4) provide the opportunity to progressively improve water supply on a hydrant that is already tapped, quickly adding to operational potential. Some of the downsides to the design of these manifolds is their cost, size, and the fact that they are steamer centric. When access to the steamer is limited or blocked, the full potential of the water access will suffer as a result.
Another simple equipment improvement at the hydrant is the addition of a gate valve to a side discharge, this will both increase capacity and versatility. In the event of blocked access to a steamer connection, accessing a single 2 ½-inch outlet for supply in a municipal system can still support the majority of fireground operations.
- At 60 psi, a single 2 ½-inch discharge alone provides 1,220 gpm
- At 80 psi, a single 2 ½-inch discharge alone provides 1,410 gpm
Accessing a single hydrant to support a single rig is a conservative and safe message but not a law. Another option that presents itself when a hydrant is dressed in this manner is the ability to support two attack pumpers where hydrant capacity is high, but accessibility is limited, such as it is in many apartment complexes. For our city, many apartment complexes are located just off of main thoroughfares and therefore the larger city water mains. It is common for us to find these hydrants providing 2,500 gpm.
When the NFPA 1710 recommendation is reviewed for apartment fire water supply, it sets a minimum of two sources at 500 gpm minimum. For our department, using four-inch supply lines and the known hydrant capacity, the system would easily support the full capacity of two lines to total 2,000 gpm.
As the picture shows, dressing the hydrants allows two supplies to feed two separate rigs in two separate locations. The orientation of apartment buildings in complexes and the exposure potential from involved units may need to be handled from multiple access points. This also allows a mulligan if the first-arriving rig laid into a poor position, the second- or third-due can hit the best hydrant and improve the position of attack without interrupting or compromising initial operations.
Local Line Selection
Determining the proper supply line selection for your organization should be deliberate. It is easy for many suburban fire departments to look at the numbers above and given their local view wonder why any department would still use three-inch supply lines when a five-inch line can provide you three times the water. Alternately, members of the urban fire department—with compartmentalized occupancies, tight streets, and well-designed, practiced and supported water supply operations—may wonder why anyone would want to deal with a massive five-inch supply line on the ground when the majority of the time you only need 500 gpm. To sum up: you be you, but make sure your choice is intentional and not simply “bigger is better”.
As mentioned before, our department uses four-inch supply lines. The single, four-inch supply line, given most of our hydrants and lays, provides the fireground with between 800-1,000 gpm. The packability of the four-inch hose allows for us to fill out hose beds to support a dual lay of the same hose, not a combination of sizes. This provides a nice and clean version of conceptual hydraulics: 1 x four-inch supply = 800-1,000 gpm (for residential/small commercial flows) and two x four-inch = 1,600-2,000 gpm (for defensive fire conditions at the aforementioned or to support larger commercial and multi-family dwelling fire flows).
By dressing hydrants with a gate valve and adapter and splitting the supply hose bed, a dual supply can be brought into the scene initially. If the hydrant is simply dressed initially with a single line laid in, a second support line can be brought in or reversed out by a later-arriving company, hand jacked back to the hydrant, or laid to a separate company at a separate location without having to shut down at the source.
Go to the Whiteboard
It would be the expectation of any chief or company officer that, if it has been awhile since a crew or a firefighter caught a hydrant, as a fundamental skill it was due to be practiced. It should be the expectation of the organization that, if it has been awhile since water supply operations have been reviewed, aas a fundamental resource, it, too, is due for evaluation. The critical nature of fireground water supply demands critical consideration.
As an ISO class one fire department, water supply is at the forefront of our department considerations. The information presented in this article and our operational decisions were a part of our most recent and past comprehensive reviews of our water supply operations. It is my hope that as presented it may help to serve as a catalyst for an important look from the source to the scene for your department. Your organization may find results guide you in a completely different direction, but the supporting documentation and experience of this type of process is invaluable confirmation of what is the best choice for your department.
BRIAN BRUSH, a 20-year veteran of the fire service, is chief of training at the Midwest City (OK) Fire Department. He has a bachelor’s degree in fire and emergency services administration and a Fire Officer designation from the CPSE. He instructs on a national level and writes for Fire Engineering