Whether it’s department SOPs, SOGs, or just the word from the old-timers, we in the fire service have rules that govern the way we do things. Especially when it comes to moving water. Some of these rules have been established from years past, while others are more recent. What are rules based on? They can be anything from fire service textbooks on water delivery to actual fireground incidents from the past that may have gone bad. Who knows? Some of you may be thinking, water flow is water flow.
Water in, water out. How or why should it change? Do you think our forefathers had the same hesitation when there was talk of trading in the buckets for hose or horses for motorized apparatus? Or, how about those darn SCBAs, only wimps use them.
Let’s take a look at different methods and techniques of water delivery that have been taught over the years based on fire service textbooks, department rules or policies, or just because. It should be noted that all techniques and operations that are going to be discussed in this article as the new alternative methods go directly in line with manufacturers recommendations for their equipment and have been used safely and successfully on the fireground.
Myth #1- The maximum flow from a 2-1/2” discharge on a pumper cannot support large diameter hose operations because of their low flow capabilities.
Reality #1- A large diameter discharge is the most efficient way to flow large volumes of water through large diameter hose. If your unit does not have a large diameter discharge, this large flow operation is still possible using a 2-1/2” discharge. The key is to use the best plumbed discharge available, preferably off the side of the apparatus with no bends in the plumbing. A large diameter hose X 2-1/2” adapter will be needed to make the connection. 1000 GPM flows should be possible at a respectable RPM range. I have been able to get 1700 GPM through a side 2-1/2” discharge with the pumper being at the receiving end of a large diameter hose relay pump operation. Yes, the RPMs needed for this operation were high, however, we did not reach the governed engine speed on the apparatus.
The 2-1/2” side discharge can flow 1000 GPM and still be an efficient operation
Myth #2- Laying a large diameter hose supply line is like taking the hydrant to the fire or like laying an above the ground water main.
Reality #2- It is this type of thinking that has gotten LDH users in trouble many times at large flow operations. Think about what that statement is saying. Basically it tells you that there is nothing that needs to be done in conjunction with the hose evolution, just lay it and it will deliver all the water that is available. This could not be further from the truth. As good as LDH is, it still needs to be used in conjunction with fire pumping apparatus, water systems and various hose evolutions. Example, a flow test was done using 500 feet of 5” hose supplied directly from the hydrant and its system pressure. A flow of 1150 GPM was obtained. We next put a pump at the hydrant to pump the water in a relay pump operation to the receiving pumper and were able to almost double the flow. We were able to produce 2100 GPM. Most departments, especially the ones using 5”, would not consider setting up a relay at just 500 feet away. They would instead just settle for what they got from the hydrant.
A simple LDH supply line evolution flow can be doubled with the use of various pump operations
Myth #3- The 2-1/2” auxiliary intake should not be used for a large flow operation.
Reality #3- I agree that it should not be used at least as the primary intake in a large flow operation, however, tests have proven flows up to 800 GPM through a 2-1/2” intake that was supplied from a relay pump operation. If large diameter hose is available, it should be used in conjunction with the 2-1/2” intake and connected by means of an adapter. The 2-1/2” intake is restrictive enough, let’s not restrict it more with small diameter hose. If all you have left is a 2-1/2” intake, use it, you may be surprised.
The performance of the 2-1/2” intake can be improved using LDH
Myth #4- When supplying a portable monitor with 2-1/2” inlets using large diameter hose, a manifold should be used at the end of the LDH line and wyed into two 2-1/2” or 3” lines for the final connection into the monitor.
Reality #4- Flow tests were conducted to disprove this myth. The first flow test consisted of 150 feet of 5” discharge line into a large manifold wyed down to two 3” lines 50 feet long and then into the inlets of the monitor. The second portion of this flow test brought the 150 feet discharge line directly into the inlet of the monitor using a 5” X 2-1/2” adapter. Both evolutions flowed 1000 GPM. The 5” by itself was able to move the 1000 GPM with 20 psi less on its engine pressure than the combination 5” and 3” evolution.
When using a master stream with 2-1/2” inlets it is more efficient to adapt the LDH line to the inlet
Myth #5- If only a 2-1/2” port on the hydrant is available, do not use large diameter hose because it will not support it.
Reality #5- I hear this a lot. As a rule of thumb, the 2-1/2” port will flow only 20% less than the large port on the hydrant when using large diameter hose.
Myth #6- Large diameter hose cannot be used on a weak hydrant system.
Reality #6- In fact it’s just the opposite. Large diameter hose would be the best choice. A weak hydrant system will more than likely be lacking good hydrant pressure, therefore the supply hose with the lowest friction loss would be the size to use to make up for the weak hydrant pressure. 5” hose has less friction loss than 2-1/2” or 3” hose.
A warf hydrant used in conjunction with LDH
Myth #7- The best supply line evolution to use on a hydrant that only has 2-1/2” ports is to siamese two short pieces of 3” hose from the 2-1/2” ports into a manifold that is connected to the LDH supply line.
Reality #7- It stands to reason that this evolution would be the most efficient, after all, utilizing two ports would flow more than one. The reality is that this type of evolution creates higher friction loss because of the short small diameter lines as well as turbulence as these lines enter into the siamese manifold. Numerous flow tests have proven that a single LDH line connected directly to one of the 2-1/2” hydrant ports will flow about the same as the evolution that utilizes two hydrant ports.
When using a hydrant with only 2-1/2” ports a single LDH line connected to one port is more efficient than siamesing two small diameter lines into one LDH line from two ports
Myth #8- A nozzle on a handline must be fully opened when in use.
Reality #8- Does this mean that if the stream is kicking your rear end on an interior attack, that you shouldn’t shut it down? The bale on a nozzle is just like the accelerator pedal in your car. The more you push on it, the faster you go. If you are heading into a sharp turn and keep the pedal to the floor, most likely you will crash and burn. The same holds true with nozzles. A gated down stream is a lot better than a fully closed stream when you absolutely need to be flowing water. Some say that the gated down stream would be broken and unusable. I say not true! We tend to evaluate streams on how pretty they look versus how effective they are. Sure a gated down smooth bore tip will produce an ugly stream, however, will that ugly stream have the reach and the volume to attack a fire? Flow tests have proven that most smooth bore tip/nozzle body combinations can be gated down to just about half way and still provide a workable stream.
Myth #9- The nozzle pressure for a smooth bore tip on a handline should be 50 psi. Pressures higher than this will produce a broken stream as well as a handline that is hard to control.
Reality #9- I’m not quite sure where this myth came from, I know it’s been around since the turn of the last century. Smooth bore tip nozzles are rated so a specific size will flow X amount of GPM at a 50 pound nozzle pressure. Successful handlines have been used with nozzle pressures reaching 150 psi. Are these high flowing lines hard to control? Standing up, yes. The key is to get on the hose in either the crouched or sitting position, thus allowing the nozzle reaction to be directed into the ground. The higher pressure smooth bore handlines are more than likely going to be used in an exterior large flow attack versus an interior attack.
500 GPM is being delivered through a 1-3/8” tip at 80# NP
Myth #10- The nozzle pressure for a smooth bore tip on a master stream is 80 psi. Pressures higher than this will create a broken stream.
Reality #10- Again, I feel that the opposite is true. Nozzle pressures higher than 80 psi can create a harder hitting, farther reaching stream that is capable of penetrating deep into the seat of the fire problem. Nozzle pressures pushing 175 have been successfully used in master stream operations. The rule to remember is to not exceed the maximum allowed inlet pressure for the appliance being used.
This master stream is delivering 614 GPM through a 1-1/4” tip at 175# NP
Myth #11- 1-3/4” handlines pumped at high engine pressures create a line so stiff that it becomes too difficult to use in an interior attack when the line needs to be advanced through hallways and rooms.
Reality #11- This may have held true years ago but with the new technology in the hose manufacturing, I think you will be surprised to see what the hose will do under higher pressures. The hose will be somewhat stiff right at the nozzle, but you won’t find a significant difference between high and low pressure line throughout the rest of the line while advancing into a structure. Try this simple test. Stretch a handline out, keeping the nozzle shut. Go ahead and throttle up to 250 psi and advance it through some type of obstacle course, whether it is in the burn tower or something you set up on the drill field. Next, try to make a real tight loop in the hose and see what you can do. I think you will be impressed.
This 1-3/4” line is being pumped at 250 psi and is able to have a 3 foot loop placed into it. Looks pretty flexible to me.
Myth #12- A low pressure nozzle used on a handline can create kinks in the hose due to the subsequent low engine pressure, which will critically restrict the flow.
Reality #12- Seeing is believing. Set up a series of flow tests to see what really happens. These flow tests should be conducted using a flow meter. Use your standard interior attack lines in conjunction with low pressure nozzles. Let’s use a 15/16” tip flowing 185 GPM at 50 pounds nozzle pressure. After reaching the flow, have one or two people place a rather severe kink in the line and then take another reading. You will find that the flow wasn’t restricted that much at all. I have conducted tests with this same scenario losing only about 20 GPM. Next, use the same 15/16” nozzle, but only flow 100 GPM and place the kink in the line again. The same thing should happen, not much change in the flow.
Myth #13- A 2-1/2” handline can flow up to 350 GPM. Flows higher than this can only be done with a master stream appliance.
Reality #13- Handline streams reaching up to 500 GPM are entirely possible using a 2-1/2” or 3” handline. A line flowing this much water should not be handled in the standing up mode, instead a minimum of two firefighters should be sitting on the line. There are several nozzle manufacturers that now market 500 GPM handline nozzles.
This 3” handline is flowing 600 GPM
Myth #14- When sitting on a handline, you must place the Keenan Loop in the hose for stability.
Reality #14- Again, seeing is believing. Set up a flow test with a 2-1/2” or 3” handline and try to get a flow of at least 300 GPM. First try it with the Keenan Loop and then without. There should be no difference at all in the stability of the line.
This 400 GPM flow does not require a loop in conjunction with the firefighter sitting to deploy the stream
It is important to have an open mind and be progressive in the fire service. The information covered in this article is just some of the ideas that I have tested throughout the years. Write your ideas down and set up evaluations to prove or disprove your theories and remember when it comes to using the equipment, do only what the manufacturer says their equipment can do.