A bright red hose attached to a red fire hydrant—Mercedes Textiles Know Your Hose Resource

Knowing Supply / Large Diameter Hose

Right-Sizing Supply 3/3 : Using Mercedes Hose to Right-Size Your Supply

Written by Captain Caleb Langer

[ This is Part 3 of a three-part series. PART 1 | PART 2 ]

Modern realities call for speed and flexibility with water supply strategies. The fire service has had great success with viewing attack packages as a whole, and departments can benefit from taking a similar “package”-based view on the supply side.

A significant part of this is to move away from a blunt, often over-sized approach to water supply, and instead focus on “right-sizing” supply strategies. This allows engine companies to be nimble and flexible, utilizing the best approach for the conditions at hand.

Mercedes has been extremely active in the move to “right-size” attack lines, with KrakenEXO SUPER II for flows in the 210-300 GPM range, and ExoMetro and KrakenEXO for smaller diameter lines. Our field specialists help departments in evaluating attack packages, assisting them in their quests to pair hose, nozzles, hose loads and practices to help them deliver a range of flows over a variety of distances in a way that is appropriate for their staffing, deployment model and built environment.

In much the same way, our specialists can assist with the evaluation of supply packages, using an informed and balanced mix of KrakenEXO and Aquaflow-Plus medium diameter lines and MegaFlo Breather large diameter hose to right-size a department’s supply strategy.


Often we hear more senior officers and firefighters reminiscing about the supply hose diameter from a generation before, saying “I wish we still had that” or “I wish we had never switched.” While this is sometimes based in sentimental thought, more often there is some merit to the thoughts and the things that have been lost in the switch to a blunt, one-size-fits-all approach to water supply.

For many departments, 3-inch hose was eliminated altogether in the switch to large diameter hose, leaving no good hose choice for delivering flows in the 500 GPM range. Such applications include feeding rapid attack monitors, supplying FDC’s, conducting tank fill operations, and providing a quick hand-stretch supply option. The trickle-down effect of this is that departments that want to switch to a right-sized large caliber handline such as Super II find themselves still needing to hang on to a bed of 2-½” hose for those operations, even though 2-½” is undersized for 500 GPM-realm flows.

Like a well-rounded attack complement, firefighters deserve to have a hose bed configuration that provides them with a user-friendly supply line for everyday incidents, but also gives the versatility to scale up by pumping those lines or even dropping a second line when the situation calls for it. By simply incorporating the option to pump a supply line at the hydrant, a department can often reduce their required supply line diameter by one size while still maintaining equivalent flows, depending on water supply infrastructure.

By also adding the option to drop a second line as needed, they can either double that flow or allow the department to further reduce their supply line size. Additionally, selecting a solid supply strategy can help make room in hose beds for an increased complement of rear attack lines including bulk loads, and provide 3” for the mid-range flows described above. Scene access can also be improved, and often a well-devised right-sized supply strategy will out-perform a single-diameter/line approach when it comes to flow.


Below is a sample of supply bed configurations that can help achieve these goals. Listed are combined flows at 20 PSI per 100’ friction loss, based on common factors, as well as 30 PSI per 100’ friction loss, for departments that elect to take advantage of higher operating pressures and/or shorter lays. For each combination of two lines, it is implied that any one of those lines can be used in stand-alone form for the majority of a department’s incidents.

    • 3” KrakenEXO or AquaFlow-Plus
      • Dual 3”: 1,075 GPM (1,300 GPM @ 30 psi/100’)

    • 3-½” MegaFlo
      • Single 3-½”: 850 GPM (1,050 GPM @ 30 psi/100’)

      • Dual 3-½”: 1,700 GPM ( 2,100 GPM @ 30 psi/100’)

    • 4” MegaFlo
      • Single 4”: 1,250 GPM (1,500 GPM @ 30 psi/100’)

      • 4” and 3”: 1,750 GPM (2,200 GPM @ 30 psi/100’)

      • Dual 4”: 2,500 GPM (3,000 GPM @ 30 psi/100’)

    • 5” MegaFlo
      • 5”: 2,250 GPM (2,750 GPM @ 30 psi/100’)

      • 5” and 3”: 2,750 GPM (3,400 GPM @ 30 psi/100’)

To support the complements above, departments or regional cooperatives may choose to equip strategically located engine companies with 5” LDH or employ dedicated hose tenders with single or multiple beds of 5” or 6” LDH. These water supply units can be dispatched on multiple-alarm fires, supporting high flows over long distances. To reflect such distances, the flows below are listed at reduced friction loss levels.

  • 5” MegaFlo, flow per line:
    • 1,100 GPM @ 5 psi/100’

    • 1,600 GPM @ 10 psi/100’

    • 2,250 GPM @ 20 psi/100’

  • 6” MegaFlo, flow per line:
    • 1,600 GPM @ 5 psi/100’

    • 2,250 GPM @ 10 psi/100’

    • 3,150 GPM @ 20 psi/100’

Like attack packages, building a comprehensive water supply package requires a significant amount of research and legwork, but the long-term operational benefits can be tremendous.

For departments that are interested in moving forward with such a project, this Mercedes' KnowYourHose.com hub is an excellent resource to gather data such as hose weights, widths, diameters and friction loss statistics to make informed decisions.

As projects move further along, Mercedes field specialists can help conduct on-site demos and assist with water supply package development, producing results that address modern fireground realities. Don't hesitate to get in touch!

About the Author:
Captain Langer joined the fire service in 1999 and has since worked for combination and career fire departments covering a range of response areas. He currently serves with the Northampton Fire Rescue Department (MA) where he holds the rank of Captain, having recently finished his tenure as the department’s training officer.

Caleb holds an A.S. in Fire Science from Greenfield Community College and is a graduate of Northeastern University’s Paramedic Program. His areas of focus in the fire service include engine company operations & water supply, fireground tactics and fire apparatus design, topics he has written on for Fire Engineering Magazine. He is rooted in a mission-oriented approach, dedicated to improving operational effectiveness.