For most of us, Labor Day signals the end of summer – especially up north where the wind is already getting cold. The pumpkin spice is out and the kids are back to school. Here at KYH, we figured we’d jump on the school bus to review the basics of knowing your hose.
We’re not talking about our hose specifically; we’re talking about the basics you should know about ANY fire hose you are considering or currently using. Particularly if you are evaluating new hose, you want to have information that allows you to compare apples to apples – as well as ensure the hose is meeting or exceeding the minimum standards.
NOTE: We encourage everyone who is on the line, and especially those on hose evaluation committees to get familiar with the NFPA 1961 requirements for fire hose. We believe having manufacturing and testing standards across the industry keeps manufactures accountable to your safety. You can get free access the NFPA 1961 / 2020. Unfortunately, the latest 2024 edition – which included some important changes – is not yet available.
SO, WHAT ARE THE BASICS OF FIRE HOSE?
First and foremost, you should know what material is being used and how the hose is constructed. The NFPA 1961 requires attack hose to be “reinforced” and “lined” – which is another way to say “jacketed” hose. A rubber/synthetic jacket is going to be very different from a woven polyester or other material. And while “extruded-thru-the-weave” nitrile/PVC or rubber is most common, not all inner liners are manufactured the same.
FYI – Mercedes’ premium structural firefighting hose are double-jacketed with an outer jacket of woven polyester treated with our Permatek coating encasing a woven inner jacket fused with our unique Mertex lining. The Mertex process ensures the hose will never delaminate – which can be an issue for some other lines. We also incorporate Breather Technology into the outer jacket on some lines to help release trapped air & water – particularly helpful in our large diameter hose.
In the North American Fire Service, most departments use some kind of woven double-jacket for attack lines, though rubber is still an option. For supply / large diameter hose, rubber is still quite common, but double-jacket is being adopted more often for its lighter weight, better packability, and durability.
Material and construction are the foundations of any hose – from there we dive into the details.
OUR TOP 7 HOSE SPECS TO KNOW:
Hose specifications – or specs – are all the detailed measurements. All of these in some way impact you on the job. Some of these affect the hose performance and are necessary for building an informed attack/supply package. That is why we publish our hose spec library here, giving you easy access.
Now, most of these are self-explanatory, but just in case, here is a rundown of our top 7 hose specs with considerations for each:
1. TRADE / LIST SIZE:
This is the category of size the hose fits – it is NOT the actual diameter of the hose. As of 2024, the NFPA 1961 lists these sizes:
- ATTACK: 1” / 1.5” / 1.75” / 2” / 2.25”* / 2.5” / 2.75”*
- SUPPLY: 3” / 3.5” / 4” / 4.5” / 5” / 6”
Adding the list sizes was necessary to ensure better standardization and avoid “size creep”. While the NFPA has previously dictated hoses could not be smaller than the trade size, it now specifies that attack hose can no longer have an Internal Diameter (ID) greater than 3/16” its nominal size, and supply hose cannot be greater than 1/2” its nominal size.
*Note that 2.25” and 2.75” are new list sizes.
2. INNER DIAMETER (ID):
This is the actual size of the inner waterway. It is important to note that waterways stretch when pressurized – which is why the NFPA now dictates Dry ID as well as Charged ID at 50 psi & 150 psi.
- DRY ID: Dry ID is the base inner diameter. Prior to 2024, there was no standard method listed to measure the ID of a hose. Now measuring the ID of a hose is done with a tapered plug gauge inserted in the end of a hose that is cut square – as outlined in UL19.
- CHARGED ID: The NFPA now requires manufacturers to publish the charged internal diameter of the waterway at 50 psi and 150 psi. As Lt. Dave Quick of Manchester FD (NH) explained on his Instagram, “The charged ID of the hose is important to know as it affects the flow range of the hose, the size of nozzle tip(s) it can be paired with (Freeman Ratio), and the amount of water in the hose (think charged weight).”
3. OUTER DIAMETER (OD):
This is the size of the outside of the hose when charged to 150 psi. While not included previously, the NFPA now requires manufacturers to publish the charged outer diameter at 150 psi. “Charged OD affects the maneuverability of the hose, especially in the medium diameter attack package (2”-2.75” hose). A smaller charged OD allows for better grip,” Lt. Quick further explained.
4. WEIGHT:
This is the weight of the hose. Most manufacturers provide the weight of the hose dry & uncoupled. This allows you to calculate the weight of the hose at different lengths.
It is important to also consider Charged Weight – as that is what you’ll be pushing/pulling at a fire. On top of nozzle pairing, this is where charged ID is important. Knowing the charged ID along with the length of the hose would allow you to calculate water volume, which would allow you to calculate water weight to add to the hose & coupling weight. (We have provided this for you in our Know Your Hose specs.)
5. FRICTION LOSS CO-EFFICIENT:
Friction Loss is the pressure lost over the length of hose at different flows – thanks to turbulence and gravity. All hose will experience friction loss. The co-efficient is the variable used in the standard equation for calculating that loss. Task Force Tips has a great resource of hydraulic calculations, including friction loss, available here. Dallas Fire Rescue Training also has a great video explainer here.
To make it easier, we have provided an online calculator for you to determine the estimated friction loss for our hoses.
6. BOWL DIAMETER:
This is the inner size of the coupling that attaches to the hose. It is generally larger than the hose diameter – as the coupling has to fit the material thickness inside. The bowl diameter is good to know when estimating hose bed sizing.
7. COIL DIAMETER:
This is the width of a coil of rolled hose and is useful for fitting bumper lines and hose storage.
AS THEY SAY – THE MORE YOU KNOW…
Beyond the above, you should also get to know:
Service / Proof / Burst Pressures ensure safety while using the pressurized hose. The NFPA sets the minimum service pressure of an attack hose at 300 psi, proof pressure of 2x service pressure, and burst pressure of 3x service pressure. Many premium hose brands exceed these minimums for your safety.
Edge Thickness / Flat Width / 180 Thickness are all used to help calculate hose bed capacity. There are no standards here – but you will find a wide variety among hose brands.
Heat Resistance when fighting fire is obviously important. As of 2020, the NFPA defined new Radiant and Conductive Heat testing requirements – and required manufacturers to provide their hose results upon request. These tests are intended to provide measurements that set an expectation for performance under exposure to extreme heat. The tests are not pass/fail and there is no minimum standard. Learn more about the new heat testing methods here.
Cold Resistance is something to consider for those living in colder climates. The NFPA requires all attack hose to remain flexible when tested to -4º F / -20º C. Special Cold Resistance is considered down to -65º F / -54º C.
KNOWING YOUR HOSE BEYOND THE NUMBERS
All of the above specs are intended to help you understand fire hose better. Armed with that knowledge, you can evaluate different lines comparatively, select the right hose for your department, build a solid attack package and then maximize its performance.
Beyond numbers, you may want to consider third-party testing, warranty terms, and even potable water safety. We certainly feel knowing a third-party agency has verified the specs provides a layer of added trust and transparency.
And even with all the above, it is always best to get hands-on – whether to demo new hose or train on your current lines. Get that pitot or flow meter out, dial it in, and run evolutions. That is how you get to Know Your Hose best.
KICKING OFF #SATURDAYSPECSCHOOL
So now we’ve schooled you in the basics here, we’re going to keep the knowledge coming on our social channels.
Each Saturday, we’ll spotlight one of our hose lines, sharing an overview and some basic specs. Follow along our #SaturdaySpecSchool on our Instagram or Facebook.