# Thread: 1-3/4 Hose Vs. 1-1/2 For fire attack

1. You know, so much of this water flow stuff distracts us from the real goal, which is not so much delivering gobs of water but placing water where it's needed. The only reason we need 150 (or 200, or however many) GPM is that we don't always have the visibility or access to make a "love connection" with the seat of the fire.

I'd bet that a pretty large percentage of the water we deliver is really just insulation--that is, with straight streams we are using the water on the outside of the stream to absorb BTU's and allow the inner part of the stream to remain in liquid form until it reaches the fire we are actually aiming for. If we could inject water directly to the seat of the fire and let steam expansion follow the heat currents through the rest of the fire, it would probably be astounding how little water we actually used. Because this is not fully possible, we still have to overkill it on water. Add to that the blind spraying we do in bad visibility and we're looking at major water usage.

And to answer the question regarding my earlier statement about weight of 1.75 vs. 1.5, I'm not sure about knockdown as we have upgrade the hose first and not the nozzles yet. Gotta start somewhere, and they don't give this crap away, do they?

2. Originally posted by EastKyFF
Some more math:

Volume of water in a 50' section of 1.5: 2.45 cu ft
Volume of water in a 50' section of 1.75: 3.44 cu ft
Difference: Roughly one cubic foot
Weight of one cubic foot of water: 8 lb
Actually, one cubic foot of water weights about 62.4 pounds. One gallon of water weighs 8.34 pounds.

3. Originally posted by Dalmatian90
Flow has to be accompanied by nozzlemanship, and I think a lot of times we've tried to keep increasing the amount of GPMs thrown at a fire as we, as a fire service, have let nozzle skills slip. Too often we throw water everywhere, some of it may actually hit the fire. Nozzlemanship can put the appropriate flow on the fire, and when you use good nozzlemanship the flows needed are often dramatically less than what is commonly instructed today.
BINGO Dal,
One of the best statements in this entire thread.
Give me my Rockwood back and let me GO TO IT

4. Yep,put out a lot of fires with a Rockwood.Learned a lot too,like when the dragon breathes back those feet had better be bi-directional.I think I'll stick to my 1.75 and SM20,the feet are getting older and the bi-directional's not as quick as it used to be.The beatings aren't as enjoyable either.T.C.

5. Originally posted by EastKyFF
Some more math:
Volume of water in a 50' section of 1.5: 2.45 cu ft
Volume of water in a 50' section of 1.75: 3.44 cu ft
Difference: Roughly one cubic foot
Weight of one cubic foot of water: 8 lb

So given a 200' preconnect, using 1.75 adds 32 pounds of water, or 75% of what my five-year-old daughter weighs. Darley's web site lists 1.5 at 17.5 lbs/50' and 1.75 at 18.5 lbs/50'. That means four pounds of extra hose weight per 200'.

Grand total: 32 pounds of water, four pounds of hose: 36 pounds heavier per 200'.
Let's try it this way:

The Volume of hose is:
V = A x L (Area times Length)
Area = (Pi x D^2 / 4) (You forgot to divide by 4)
The Area must be expressed in square feet.

Therefore, for 1-1/2" Hose:
A = Pi x [(1.5/12)^2] / 4
A = 0.01227 Cubic Feet
V = 0.01227 x 50Ft
V = 0.6136 Cubic Feet
Density of Water = 62.4 lbs/cubic foot (as erics99 stated)
Weight of Water = 0.6136 x 62.4
Weight of Water = 38.3 lbs in 50 feet of 1-1/2" hose
Weight of Water = 38.3 x 4 = 153.2 lbs in 200 feet of 1-1/2" hose

For 1-3/4" Hose:
A = Pi x [(1.75/12)^2] / 4
A = 0.01670 Cubic Feet
V = 0.01670 x 50Ft
V = 0.8352 Cubic Feet
Density of Water = 62.4 lbs/cubic foot
Weight of Water = 0.8352 x 62.4
Weight of Water = 52.1 lbs in 50 feet of 1-3/4" hose
Weight of Water = 52.1 x 4 = 208.5 lbs in 200 feet of 1-3/4" hose

Weight Difference of water = 208.5 - 153.2 = 55.3 lbs

Note the Density of water at 50 F is 62.4 lbs/ft. It varies slightly with temperature changes.

I prefer the equation: WD = 17(D^2 - d^2) to determine the Weight Difference.

6. ## automatic nozzle

If you have the right size automatic nozzle you should use an 1-3/4" hose. Alot of fire can be put out with this combo but be careful because you'll drain your truck fast if your not.

7. FYI on the numbers...or "let's talk about the physics of the situation"

The "perceived" increase in difficulty will probably be more than the raw weight gain alone.

Because that weight is distributed along the length of the hose, and it's not only more weight for you to pull, but it will cause more friction along the entire length of the hose (more weight pushing the hose against the floor more "firmly" if you will).

If we guess at normal hose on a carpeted floor being roughly equivelant to wood sliding on wood, it's a 50% factor. If you're horribly unlucky and have rubber-jacketed hose on dry concrete, it's a 100% factor. i.e. those 55 extra pounds will probably feel like 75 or 80 extra pounds when you're actually pulling the line due to friction.

Which is why some of the premium attack lines, like Angus Hi-Combat, tout their "slipperier" jackets -- less friction on the jacket, the easier it is to pull.

Of course, this is a complicated situation to model, because other things can make your pulling on the hose hard, such as having to pull it through one or more tight turns. People may complain about higher pressures in line (150, 200psi) being more difficult to handle, but on the flip side those might be easier to pull since they'd kink less on corners.

Just food for thought

8. upinflames60...

The RIGHT automatic nozzle? Well, some may argue there is no such thing, but for the sake of argument the type of nozzle is irrelevant. It is the flow capability of the nozzle and not the type of nozzle that matters. A single gallonage nozzle that flows 150 gpm or more, a low pressure nozzle that flows 150 or more at 50-75 psi, or even a smoothbore of 7/8" or greater is also a very good choice for 1 3/4" hose. Any nozzle capable of a flow in the range of 150-200 gpm is an appropriate choice.

FyredUp

9. Whoopsie-doo on my math!! Thanks for the correction...forgot that convert-cubic-feet-to-gallons step. That was a big difference.

10. I feel that it would be an asset to the department, but the union feels that it is to heavy and that 1-1/2 hose is sufficient for our purpose
Lord knows I don't want to start a union/non-union debate here, but anyone see a problem with this statement? No calculations, no scientific approach, no "let's try it out and see how it works". The union don't like it, end of discussion. "200 years of tradition unimpeded by progress". Indeed.

That being said, we phased out most of our 1.5" a long time ago. Been using 1.75" as our primary attack line for almost as long as I've been with the department, with 1.75" nozzles of course. I like the increased volume and I don't think it's that difficult to handle, even for an out-of-shape slug like me. Really, for anyone who's been in our department under 15 years or so, 1.75" is what fire hose is supposed to feel like. They've never even used 1.5". Maybe if we tried 2" they'd complain, but 1.75" is what they "grew up" with.

I'm sure the first guy who suggested we should quit using booster reels got much the same reception.

11. Dalmatian90, you have raised some good points. Although the initial post seemed to be interested primarily in the weight issue, a comparison between a 1-1/2" and 1-3/4" hose includes an analysis of several factors:
1. Hydraulics
2. Logistics
3, Cost

Regarding hydraulics, one must consider the desired flow rate. If one desires 200 gpm, the 1-1/2" quickly becomes impractical. If 125 gpm is needed, the 1-1/2" is a viable option. Also, if larger flows are needed, what are the nozzle reaction forces (fog vs, smooth bore).

Logistics include (1) storing it on the engine and (2) maneuvering the hose line.

(1) If you currently have 200 feet of preconnected 1-1/2", can you accommodate 200 feet of 1-3/4" in the same space?)

(2) Maneuvering the hose involves several issues:
(A) Weight - This has been covered in previous posts.
(B) Kinks - How susceptible are each to kinking?
(C) Nozzle reaction forces. This varies with fog nozzles (50, 75, 100 psi) and smooth bore nozzles of various diameters.
(D) Manpower - Does the 1-3/4" line require more manpower?

The weight issue involves not only a vertical lift, but also friction forces. Seldom does one have to lift (vertically) 200 ft of hose. Also, seldom does one have to drag the entire length of a charged 200 ft preconnect. The last 50 to 100 ft of the hose is typically what has to be dragged. The frictional resistance is based on the coefficient of friction (which is what Dalmatian90 was describing) and the weight of the object - not the surface area. Pulling a hose line up the stairs involves overcoming friction forces and the vertical weight.

Cost: Looking at the cost of 1-1/2" versus 1-3/4" I found a cost difference of \$10 to \$15. I am sure with the number of distributors available, there are other values.

All of this requires some number crunching based on what is available t oyour department.

There is probably something I forgot, so add to the list.

Dalmatian90, you’re dissertation on fire development is very interesting and I would encourage you to start a new thread on the subject.

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