A recent article about a Lake County, Florida fire truck accidentally laying 1200 feet of firehose down the middle of the Florida Turnpike and causing damage to a number of cars made me want to post about the old days when I still did that sort of thing.
The hose that runs from the fire hydrant to the fire truck is called supply line. Most supply line is 3 inches or more in diameter, and in Central Florida, it’s usually 5 inches. (Orlando uses 4 inch, but that is because they typically have fire hydrants that are close together).
First, a bit of engineering.
The reason for this is hydrodynamics and friction loss. The average water main pressure is about 65 psi. At 1,000 gallons per minute, a 3 inch hose loses 80 pounds of pressure every 100 feet of hose length due to friction between the moving water and the hose itself, while a 4 inch diameter hose loses 20 pounds of pressure, and a 5 inch hose loses only 8 pounds. That means, if you want longer hose lays with high flow, the larger the diameter of your supply line, the better.
There is a lot of math involved in being the driver of a fire engine. You need to be able to calculate your friction losses in your head, rapidly, and remember that the lives of the guys in the burning building depend on you getting it correct. When you are flowing 2,000 gallons per minute through half a dozen different hose lines a 2 in the morning at a burning strip mall isn’t the time to realize that you are math deficient.
5 inch supply line has what is called a “sexless coupling” meaning that there is no male or female end, the couplings are interchangeable. This allows you to start laying from either the fire to the hydrant, called a reverse lay, or from the hydrant to the fire, called a forward lay. There are advantages and disadvantages to both, but we won’t talk about that in this post.
My fire truck carried 1200 feet of 5 inch diameter supply line. That means with standard hydrant pressure, I could get a bit more than 800 gallons per minute into my engine without having to put another fire engine at the hydrant to boost pressure.
The problem with this is twofold:
- 5 inch hose is heavy. Each 100 foot section weighs a bit more than 100 pounds without water in it. Filled with water, that increases to over 1,000 pounds.
- 5 inch hose is bulky. The hose itself lays flat, but the couplings are a pain. The hose has to be loaded on the truck in a specific way, or it won’t come out of the truck correctly.
Both of these issues mean that 5 inch is a pain in the ass. It’s worth it, but that is not much consolation when you have to lay and reload 1200 feet of it. Anyhow, if loaded correctly, that hose comes out of the truck like a scalded dog. Like so:
I sympathize with the guys that this happened to. I once laid all 1200 feet of my supply line without meaning to when I was on the way to a large multi alarm fire. We hit a bump, the hose began laying out, and I dumped all 1200 feet in the middle of the road.
There was another time that the water department had removed a hydrant without telling the fire department. I arrived at a fire at 2 o’clock in the morning with the assignment of “secure the water supply.” I decided to do what is called a reverse lay.
So I began laying my supply hose at the fire, and headed to where I thought the closest hydrant was. 1,000 feet later, I arrived at where the hydrant was (or so I thought) and it was no longer there. After the fire was out, the other guys on the engine were not happy with me at all as we loaded all thousand pounds of hose back onto the truck.
The reason for that, is the hose is loaded by the driver backing over the hose as firefighters standing on the back of the truck lift it and load it back on the truck. The driver doesn’t do a thing but drive, the firefighters load the hose. I wasn’t a popular guy that night…
For those who are interested, the amount of hose and other equipment carried on the engine I was assigned to for the last six years of my career as a firefighter was pretty impressive. We had:
- 1200 feet of 5 inch supply line
- 300 feet of 3 inch supply line
- a single 30 foot piece of 5 inch supply line in the side running board
- a 250 foot length of 2 1/2 inch line preconnected to a smooth bore nozzle (cross lay)
- a 300 foot piece of 2 1/2 inch line preconnected to a gated wye
- a pair of 1 3/4 inch line that were 200 feet each, with nozzles connected to them (cross lays)
- a 100 foot long 1 3/4 inch “trash line” on the front bumper
- another 200 feet of 2 1/2 inch line, and 300 feet of 1 3/4 inch line in the storage compartments.
- a “high rise pack” with another 200 feet of 1 3/4 inch hose in it.
That comes to 4,000 feet of hose. Plus all of the connectors, hose tools, breathing apparatus, spare air bottles, medical equipment, thermal cameras, 100 gallons of various types of foam, a set of hydraulic rescue tools, air tools, hand tools, flashlights, a gasoline powered fan, a power saw, extension cords, 2 chain saws, 6 axes, a set of pneumatic lift bags, 2 cases of Gatoraide, 2 boxes of energy bars, and a dozen other tools. The truck itself has a 1500 gallon per minute pump, a 10 kw generator, and 1,000 gallons of firefighting water onboard. In all, there were more than 10,000 pounds of equipment and supplies on that truck.
I loved driving and working off of that engine. I did everything on that truck- I rode as firefighter, paramedic, driver, and even as the officer in charge. There are times that I miss doing it. Life was easier and less complicated then. All I had to do was put the wet stuff on the red stuff.