Working With Large-Diameter Hose, Part 2

Part 1 was published in the January 2000 issue. It covered the attributes of LDH and safety and efficiency considerations when using it.

For many of us, practically all of our water supply hoselays are performed from hydrant to fire, a forward lay. In this age of large-diameter hose (LDH), most of the time, engines no longer have to pump hoselines at a hydrant. We have already examined the advantages of a forward lay. Now, let’s look at some disadvantages.

The engine “backs down” toward the fire.

Engines that lay in their own supply line can turn the fireground into a parking lot for fire apparatus. This becomes a real problem in congested areas that already have limited access such as garden apartment complexes, shipping terminals, lumberyards, and alleys at the rear of strip shopping centers. Where space is at a premium, it should be reserved for ladder apparatus, not jammed with engines. Engines that forward lay into the fire scene increase their exposure to radiant heat, collapsing walls, falling glass, downed power lines, and hazardous materials. We should not be so accustomed to forward laying LDH that we fail to recognize those situations, rare as they may be, in which a forward lay can get you into trouble because it blocks access, places the apparatus and pump operator at risk, and limits water supply.

The company pulls the LDH.

A reverse hoselay places the engine at the hydrant; both are connected by a short section of suction hose. This takes greater advantage of the hydrant’s water supply and the apparatus’ pumping capacity. An engine positioned at a hydrant allows it to pump the supply line(s) at a higher pressure than is possible with the hydrant alone. This helps to overcome the friction loss in the hose, pushing a greater volume of water a farther distance. Departments using four-inch LDH will realize the benefits of a reverse lay more often than one using five-inch hose. The reason for this, of course, is the greater friction loss in four-inch hose and, hence, the need to pump it more frequently at higher than hydrant pressures.

The 2 1/2 inch “skid load”.

A reverse lay evolution begins with a company’s locating and checking the hydrant before putting hose on the ground. This ensures that the hydrant works and that the company has found the closest hydrant, or perhaps a more distant hydrant capable of flowing more water. Another advantage over a forward lay is that it prevents you from forward laying a large quantity of hose to a hydrant you thought was the closest (I’ve already laid more than a thousand feet of hose from what I thought was the closest hydrant only to spot one much closer to the fire). A company about to reverse lay should consider backing the apparatus toward the fire. This positions the hosebed toward the fire and the apparatus in the direction of travel toward the hydrant.

You may be reading this and thinking, This all sounds good, but reverse lays take too long! I’ll agree that forward laying in a supply line and pulling a preconnect gets water on a fire faster than dropping hose at the fire and then driving back to a hydrant-no argument there. For a fast attack on house fires, a forward lay is definitely the way to go, especially if you start water from the booster tank before you receive water from the supply line.

I believe, however, that many departments take too long to reverse lay hose for two reasons. The first is that they don’t practice it enough. Spring a reverse lay on your company during your next drill. If they look like the Keystone Cops, it’s time to practice reverse lays. The second reason is that apparatus on many “preconnect fire departments” are not set up to facilitate a reverse lay. Consequently, they must scramble to disconnect preconnects to improvise as skid or static loads. Choosing a reverse lay over a forward lay can be a trade-off: You’re willing to take the extra time in exchange for additional water, safety, and more efficient use of engine and aerial apparatus. Because a reverse lay may take more time than a forward lay, fire officers must accurately project the spread of fire to make sure that companies have water before fire has overrun their positions.

For reverse hoselays, a gated manifold, or “portable hydrant,” is like having a pumper right at the fire scene. With one LDH and up to four 21/2-inch outlets, the manifold can supply and control the flow to handlines, master streams, and other apparatus. When hand-lines connected to the outlets are relatively short (within 200 feet), start pumping the manifold at 100 psi for smooth-bore nozzles, 150 psi for fog nozzles. Get water flowing. Then you can calculate your friction loss and “fine-tune” your discharge pressure. Remember, don’t exceed the pressure rating of the hose, however.

Although quints have the capabilities of an engine and ladder apparatus, they tend to be quite large and cumbersome, especially when they must be used as an engine in their first-due district. It’s tough enough to maneuver a large quint down a narrow alley or into a crowded garden apartment complex. Providing a quint with a water supply can be even more difficult. Consider the following scenario: A quint is ordered to operate its elevated stream at the rear of a fire building. The quint could take its position (at the rear of the building) and wait for an engine to back down the alley and then reverse lay a supply line, but that would be extremely time-consuming and may take more hose to reach a hydrant than the engine carries.

To speed up the process, the quint and subsequent-arriving engine will perform a combination of a forward and reverse lay and use a combination of conventional and LDH. The quint will forward lay its own dual three-inch supply lines as it drives down the alley toward the fire. Now, an engine equipped with LDH can remain on the street, connect the quint’s three-inch lines to a manifold, and reverse lay the LDH to a hydrant.

A company operating a quint as a first-arriving engine company should consider dropping its own hose at the street entrance to a congested driveway, alley, or anywhere else that it will take too much time and hose for another company to lay them a supply line.


Although it is big and heavy, a portable manifold can increase the effectiveness of LDH, whether you forward or reverse lay. The manifold functions as a large wye or water thief, dividing the flow of one LD hoseline to supply two apparatus, two portable heavy-stream devices, or four handlines. Valves on the manifold control one LDH and four 21/2-inch outlets. This allows lines connected to the appliance to be charged and shut down right at the fire scene instead of hundreds of feet away at a hydrant or pump panel. The portable manifold also functions as an in-line gate valve, controlling the flow of LDH connected to apparatus at the fire scene. Typically, the manifold is connected to the supply line, and then the apparatus is connected to the manifold with a short pony section of LDH.

Using a manifold would have prevented the following situation: A quint puts its elevated stream to work on a strip mall fire. It receives water from an LD supply line connected to its front intake. Fire conditions intensify, necessitating that the quint be repositioned. Since the firefighters did not have the control of a manifold, they will have to run down the street and shut off the hydrant to disconnect the LDH from the quint or, if they can gather enough firefighters, they may be able to lift and carry the charged supply line while it is still connected to the moving quint-quite a task. The firefighters chose the second option and managed to lift the charged five-inch hose. The sight of all those firefighters carrying the line vaguely reminded me of a conga line at a wedding reception.

Many fire departments strictly forward lay their LDH and use it as if it were a long soft-suction hose-connected from a hydrant to the intake of a pumper at the fire. That’s fine, but we have learned that a portable manifold placed in the supply line allows more versatility:

  • It serves as a hose clamp.
  • Connecting a manifold allows a supply line to be charged before it is connected to the pump’s intake, freeing the firefighter at the hydrant and facilitating the use of short pony sections of LDH.

Because most LDH comes in 100-foot sections, an engine company may have to pull as much as 80 feet of excess hose just to reach its pump intake. That’s a lot of hose that can cause kinks and block the street. The alternative is to connect the portable manifold at the first coupling behind the apparatus, charge the supply line from the hydrant, and then select a short section of LDH to connect between the manifold and the pump intake.

  • Connecting a portable manifold allows two pumping apparatus to be connected to the same supply line. This works well in the scenario in which an engine company is first to arrive at a serious fire that will require the use of an elevated master stream. The engine forward lays an LD supply line and either stops short or pulls past the fire building, reserving the front of the fire building for a later-arriving quint. The engine connects its portable manifold to the supply line and connects one or two three-inch hoselines from the manifold to the intake of its pump. This will supply the engine with enough water to operate preconnects to protect exposures. Now, when a quint (or TelesqurtT) arrives, it can take a position in front of the fire building, connect its suction to the unused LDH port of the manifold, and receive sufficient water to operate its elevated stream on the main body of fire.

Be careful when connecting a portable manifold. It may be big and heavy, but it can flip over and whip if it is attached to hose that is twisted or has too much slack. Remove slack, bends, and twists before charging the line. Also, LDH undergoes considerable elongation when charged. I’ve seen it move as much as four feet. This property of LDH must be considered when connecting it to appliances and apparatus. For example, connecting a portable manifold too close to the tailboard can result in the appliance’s being pushed under the apparatus when the line is charged. Also, be careful when standing in front of a large manifold while LDH is being charged. It can knock you down.


Water hammer is a constant danger of LDH and must be prevented by opening hydrants, manifolds, and discharges slowly. The sudden rush of water gushing through LDH can violently twist and whip the hose, damage heavy appliances, and cripple firefighters. It’s a good idea to crack open valves just enough to allow the entire line to partially fill with water before opening the valve completely. National Fire Protection Association (NFPA) standards now require valves three inches or greater in size to operate slowly-in no less than three seconds. However, many valves on existing apparatus and appliances do not meet that standard. Therefore, anxious firefighters must resist the urge to “send the water” too quickly. NFPA standards now require that LDH couplings be equipped with locks, which allows the couplings to be connected and disconnected by hand but prevents them from accidentally disconnecting.

Unfortunately, we purchased most of our LDH before locking couplings were required. We must, therefore, watch out for worn couplings that fit together too loosely; otherwise, they can accidentally disconnect when they hit the street. As mentioned previously, twists in LDH can cause it to uncouple itself. Short pony sections are especially prone to accidentally disconnecting. I believe that this is because they are not long enough to absorb any twisting. Unfortunately, the short sections are most likely to break a knee cap if they disconnect-that’s because they’re usually connected to pump panels, hydrants, and appliances where firefighters are standing. Be very careful to take the twists out of short sections of LDH; look into retrofitting them with NFPA-compliant locking couplings.

New apparatus designed for LDH will have one or more large-diameter discharges fitted with storz couplings. Existing apparatus equipped with only 21/2-inch discharges can also pump LDH with the use of a 21/2-inch LDH adapter. Flows exceeding 1,000 gpm can be readily achieved by connecting five-inch hose to a 21/2-inch discharge with a 21/2- 2 five-inch storz adapter and pumping at 150 psi EP. Selecting the proper 21/2-inch discharge is, however, important. Make sure to use discharges with the shortest, most direct, and largest diameter piping from the pump. This usually requires connecting to a side discharge and rules out using discharges piped to the rear of the apparatus. Also, for safety, it’s a good idea to connect LDH discharge lines on the right side of the apparatus-opposite the pump panel. Many pumping apparatus manufactured today are equipped with front, side, and rear LDH intakes. This makes it very convenient to connect supply lines. But look at your front and rear intakes. What diameter is the piping? How long is it? Does it have several abrupt bends? On many apparatus, including ours, piping for front and rear intakes is only four inches in diameter. That restriction is not a problem most of the time. However, when water supply is critical, connect directly into the pump “steamer” intake instead of at the front or rear. We’ve found that we can get at least 300 gpm more by connecting the supply line right at the pump panel.

Connecting your supply line right at the pump panel has another advantage, although it may not meet the approval of some of today’s “high-tech” firefighters in this age of the laptop. Most of us were taught to always maintain 20 psi residual pressure on the intake side of the pump. This is a good rule; it ensures that water demand does not exceed supply and prevents destructive cavitation. But a compound gauge is just one indicator of residual pressure and should not be relied on by itself. The tachometer and master pressure gauge can also indicate if your residual pressure is adequate: If the pump pressure rises with an increase in revolutions per minute (rpms), water is still available. No corresponding rise in pressure indicates that you should back off on the throttle because you’re approaching cavitation.

Then there is the “ol’ reliable” indicator of residual pressure that doesn’t rely on any gauge. Years ago, when my dad was a firefighter in Chicago, an engineer taught him not to rely on the pressure gauges of old spare apparatus, which were seldom accurate. The engineer taught my dad to determine if the residual pressure was adequate by stepping on the intake hose: If it was hard, the residual pressure was “okay”; if the suction hose was soft or starting to collapse, you’d better “throttle back” because the pump was approaching cavitation. That method for checking residual pressure is as accurate now as it was 50 years ago.

Using firefighting equipment safely and effectively requires being familiar with it and repetitively training in its use. This is particularly true with LDH. LDH has a remarkable ability to move large volumes of water, but don’t expect it to handle or behave like conventional, smaller-diameter hose. LDH requires specialized equipment, new procedures, and repetitive training to maximize its advantages and minimize its disadvantages.

Thanks to Chief Dave Brooks, who provided technical assistance for this article.

BILL GUSTIN is a captain with Miami-Dade (FL) Fire Rescue (formerly Metro-Dade) and lead instructor in his department’s officer training program. He began his 27-year fire service career in the Chicago area and teaches fire training programs in Florida and other states. He is a marine firefighting instructor and has taught fire tactics to ship crews and firefighters in the Caribbean. He also teaches forcible entry tactics to fire departments and SWAT teams of local and federal law enforcement agencies. Gustin is the author of the video Fighting Car Fires (Fire Engineering, 1998) and the forthcoming video Search and Rescue in Private Dwellings. He is an editorial advisory board member of Fire Engineering.

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