A bright red fire hose is connected between a fire hydrant and a fire truck—Mercedes Textiles Know Your Hose Resource

Knowing Supply / Large Diameter Hose

Right-Sizing Supply 2/3 : Considerations for Jacketed Large Diameter Hose

Written by Captain Caleb Langer

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

In recent years, the fire service has seen a trend toward use of jacketed hose for large diameter supply lines. This practice allows for higher service pressure ratings and improves packability, among other traits. When making this choice, however, it is important for departments to be aware of potential issues and the steps they can take to address them.


One common issue that departments encounter with jacketed LDH is the tendency for it to accumulate a significant amount of air between the jackets, which can be a hindrance when it comes to packing, especially in tight hose beds.

Mercedes designed the MegaFlo Breather product line with “breather” strips to allow air trapped between layers to vent, improving packability.


Another concern with many types of jacketed supply line is the risk for delamination of the liner from the inner jacket. Delamination is among the most concerning of failures due to its sometimes-elusive nature. Delaminating hose will often pass annual pressure testing without issue but can create intermittent or permanent flow obstructions unbeknownst to the user.

The NFPA 1962 requirement to flow-test attack lines helps bring these issues to light with smaller diameter lines, but since there is no flow test required for supply hose, a department may not become aware of flow reductions caused by delamination, simply assuming they are at the limits of their water supply.

Thankfully, this is another area that Mercedes has addressed for end-users: the unique Mertex lining introduces the polyurethane liner through an extrusion process as the inner jacket is being woven, making the two inseparable, thus eliminating the risk of delamination and its implications on the fireground. From the standpoint of protecting a department’s capital investments, this manufacturing process allows Mercedes to back Megaflo products with its signature 2-10-L warranty, which includes two years of all-hazards protection, ten years against manufacturer defects, and significantly, a lifetime warranty against delamination.


Given the size of large diameter hose and the standard practice of using 100’ lengths, weight is another issue to consider. With many brands, it is common for uncoupled LDH to weigh over 80 lbs per 100’ for 4” and more than 110 lbs per length for 5”.

Like other Mercedes products, the Megaflo Breather line offers a premium hose with excellent weight savings. Megaflo 4” clocks in at 0.68 lbs per foot uncoupled, and 5” at 0.86 lbs per foot uncoupled, representing a significant weight reduction compared to other models of both jacketed and rubber supply lines.

To carry this benefit further, Megaflo products come standard with Permatek HP treatment, which helps to resist moisture pickup. While other jacketed hose products can become water-logged and significantly heavier after use on the fireground, Mercedes’ Permatek treatment helps minimize this effect to keep the hose workable. Additionally, Permatek HP helps resist abrasion, a common threat to supply hose, and also resists mildew formation, which is always a factor when jacketed supply hose may need to get reloaded wet.


On most engine company apparatus, space in the hose bed is at a premium. For some departments it’s a matter of being able to fit more lengths of hose than they previously carried. For others, they are looking to add in bulk attack lines and/or reintroduce medium diameter hose as part of their arsenal. Even when the volume or complement of hose isn’t changing, simply having hose that packs well enough so that it fits more comfortably and cleanly in the bed is a desirable trait.

Like other Mercedes products, the design of Megaflo Breather, Aquaflow-Plus and Kraken supply line products keep packing dimensions streamlined. Fold thickness is minimized, which increases the amount of supply line that can be carried in a given bed, reduces the risk of hose binding up in tighter beds, and reduces the top of the load height.

Lay flat widths are also reduced compared to other products on the market, which can make the difference in being able to fit an additional stack of hose that’s desired in a bed. And when it comes to the storage of pony length sections, the tighter coil diameters of Mercedes supply hose reduce the storage profile of rolled hose in hose troughs and compartments.


The dry properties of hose are important, but ultimately fire hose is designed to flow water! When it comes to supply line, friction loss characteristics dictate how a given line selection will perform for a department, and hose construction has an impact on hydrant connections and hose movement.

Fortunately, Mercedes supply line products offer considerable benefits once the line is charged as well. The Mertex lining provides exceptionally low friction loss, offering more than 20% greater flow in 4” and 5” sizes compared to conventional friction loss numbers. The pliability of the hose construction combined with its kink resistance allows for a tighter bend radius when making hydrant connections, and these attributes combined with low ground friction make it easier to move when it becomes necessary to reposition an LDH supply line.

Jacketed supply line will likely become even more popular in the coming years, as departments initiate capital projects to phase out older generations of rubber LDH. Gathering data and performance information, and evaluating products on the market will help end users make the best choices to equip their organizations.

In Part 3, we’ll look at some factors with even larger implications for those departments formulating their hose replacement plans, as we discuss ideas to right-size your supply strategy.

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.