WATER SUPPLY CONSIDERATIONS WHEN PUMPING TO LADDER PIPES
Some recent fires in the City of Dallas have revealed an opportunity to develop stronger tactics during defensive operations - i.e., when we are flowing ladder pipes.
Before we continue, we need to establish some essential guardrails for this conversation. These considerations are limited to how they address the problems identified below. Within the context of my department, these tactics would carry little to no significance at fires where 1) hand lines are used for extinguishment or 2) when hydrants are within 100-250’ of the attack engine (because of our water supply system). Further, these considerations are only that… “considerations.”
IMPORTANT NOTE - These considerations were developed within the context of my home department. Although the principles apply broadly across the fire service, they must be considered within your department’s context, resources, operating procedures, etc. In no way are these considerations intended to replace what you are expected to do within your individual agency.
Identifying The Problem
“We’re [running] out of water” is a frequent radio transmission at larger fires in which we have gone defensive and are now utilizing ladder pipes or multiple master streams to gain control of the fire. With each line that goes into service, our Driver Engineers monitor their compound gauge, watching it drop closer and closer to that “line of no return” — 20 psi. As our ICs call for more water or bigger lines to be put into service, our Driver-Engineers must determine whether or not they have enough water to supply the request. If it pushes them under 20psi on their intake gauge, most will “tap out” (correctly) and notify the IC that they cannot fulfill their request.
It’s only after the fire, once we’ve picked up all the hose and returned to the station, that we might be asking ourselves if there was something else we could have done differently to get more water.
Were we really out of water?
Did we really “bleed that hydrant dry?”
If we were to walk into the house or building next door and open a faucet, would water have come out?
What I am proposing here is that the answer to these questions is that we were NOT out of water. In fact, we had plenty of water still in the ground to utilize. Further, If we had walked next door and opened a faucet, water indeed would have come out, just as it usually would.
Our most significant issue at these fires is typically NOT that “we’ve run out of water” at the hydrant. Instead, our issue is that the water coming from our hydrant has slowed down due to friction loss to the point that it cannot match our desired output. We’re simply not bringing water into our engines fast enough to flow the desired volume of water necessary.
So, what is causing this to happen?
The issue is in our 5” supply hose. More specifically, it is due to the friction loss generated inside that 5” supply hose, as large volumes of water are being forced through more than four sections of hose. It is important to remember that friction loss is volume-dependent. The greater the volume, the greater the friction loss. Conversely, the lesser the volume, the lesser our friction loss.
5” hose is bragged on by manufacturers and even highlighted in our rookie school IFSTA books as hose with minimal or “next to nothing” friction loss. This is true, but only at lower volumes. For example, when we are flowing under 500 GPM, the friction loss in 5” hose IS next to nothing, equating somewhere between 1-2psi per 100’. However, as the figure to our right shows, once we move past 1,000 GPM the friction loss we experience begins to increase rapidly.
Pressure and Velocity
Our Engine’s pump is designed to impart velocity to the water it receives. Water comes in... our pump speeds it up... and it is spit out the discharge side. On our pump panels, though, we don’t have a feet-per-second (fps) gauge; instead, we measure a byproduct of that velocity — pressure. Pressure is the measurement we can capture and visualize on our pump panels. This is why we don’t regularly talk about the “speed of water,” but rather the pressure in our pumps, hose, etc — because pressure is what we see on the gauge, not velocity.
But don’t let that misguide you. Velocity, or the speed of water, is THE CRITICAL issue when we are battling larger fires that require ladder pipes. The issue is that our water is slowing down before it hits our pumps due to the friction loss in our 5” supply hose. We can see this on our intake/compound gauge as it bottoms out, and we’re left telling the Chief, “we’re out of water.”
But the reality is… we haven’t run out of water. Rather, our water has slowed down too much!
Friction Loss Is Slowing Us Down
Let’s move a bit more granular and consider what our friction loss in 5” LDH is when we are flowing 1,200 and 1,500 GPM:
Armed with these facts, let’s consider what our hydrants are producing in terms of pressure and how this friction loss in our LDH impacts (or slows down ) our water supply.
Most hydrants in my city provide somewhere between 60 and 90 psi at the hydrant. Now, as we can see in the chart below, once we start flowing ladder pipes (~ 1,200 GPM), the friction loss on the intake side of our pumps (what is between the hydrant and our engine) starts to run away from us, increasing to the point that the pressure our hydrant was initially supplying us with is now, wholly negated.
Now consider this… If we have 500’ of 5” LDH on the ground, being supplied by a 60psi plug that is flowing 1,200 GPM, our intake gauge will be dang close to 0psi. Most Driver-Engineers do not feel comfortable, and rightly so, running at this pressure and will opt to either under-supply the ladder pipe so that they can maintain at least 20psi on their intake gauge or radio the IC that they cannot supply the Truck at all.
60 psi from the hydrant - 60psi of friction loss in 500’ of hose = 0 psi at your intake gauge
Now, if the hydrant is putting out closer to 90psi in this scenario, our intake gauge will sit somewhere closer to 30 psi. This situation is much better than the previous, but also leaves little room for additional lines to be put into service and will cause most Drivers to again radio, “We don’t have enough water to supply that,” when the IC calls for additional exposure lines.
90 psi from the hydrant - 60psi of friction loss in 500’ of hose = 30 psi at your intake gauge
Clearly, the issue is that friction loss is slowing our water down when we try to put 500’ of supply hose between our engines and the hydrant.
So, if the issue is that our water is slowing down due to excessive friction loss in our supply hose, what is the solution?
The solution is to speed up the water.
How do we speed the water up, then? The answer is to place an Engine as close to the hydrant as possible and pump to the attack engine supplying our Ladder Truck. In doing this, we are increasing the speed of our water, which translates onto our pump panel gauges as pressure.
This process is called “pumping off the hydrant” and allows us to move the hydrant right next to the attack engine effectively. We’re adding a “pressure margin” to the attack pumper so that when we begin pumping to our ladder pipe, the water still has plenty of speed coming in to supply not only the ladder truck but several other lines potentially.
“Plan A”
Putting SOLUTIONS Into Action
If we are going to proactively address this potential problem at working fires that require defensive operations and the use of ladder pipes, we need to develop strong water supply tactics from the onset. For our Chiefs, Officers, and Driver-Engineers, any time we are anticipating the use of ladder pipes, we should set up from the start by placing an engine at the hydrant.
Depending on your response model, response time, and equipment/appliances, this can be accomplished in several ways:
If your department utilizes HAVs (hydrant assist valves), any engine would able to connect to the hydrant and then forward lay to the fire. A supply engine would then be placed at the hydrant to tie into the HAV and begin the process of pumping to the attack engine, or the engine that is supplying the master streams.
Without the use of a HAV, a basic forward lay by the initial attack engine could still be utilized. However, the attack engine SHOULD NOT connect to the hydrant, but only wrap the hydrant (with no connection made) and then proceed to the fire. The hydrant would then be tied into by the second due engine using a “heavy hookup” (see Appendix B). The supply line that was wrapped and laid in by the previous apparatus would be connected to the supply engine’s discharge and pumping would ensue.
I struggle with this because, in my mind, it delays immediate action by the first due engine at the fire scene. There will be times when it is prudent to bring your own water, however, in most situations, I believe water supply is best done by the second or third due engine.
Here in Dallas, we do not have HAVs, and our first-due engine is almost always going straight to the fire. It is thus the responsibility of the second due engine to “bring water” to the attack engine. The best option here though would be to have the second-due engine wrap the hydrant (without connecting) and forward lay into the scene. The third due engine would then move up and make the connection to the hydrant and then pump to the attack engine (or to the second due if you wanted to create pressure planes which is a whole other topic we will discuss in a later article).
*** It is important for me to qualify something here — I am NOT advocating that we delay initial fire attack operations or search/rescue operations in order to set up these water supply evolutions. Water in the tank exists for a reason. Life safety is our highest priority!
Plan B
Let's assume that, for some reason, the first due IC misjudged the potential need for defensive operations that require ladder pipes. Because the second due engine was called to "bring water" and utilized a forward lay that was greater than 200', we need to have a Plan B so that we can still implement "big water tactics."
The second due engine will almost assuredly not be part of this solution. Therefore, as command is passed and the need for ladder pipes is recognized, we must notify the third due (or call for an additional engine to be added to the alarm) that they must reverse lay back to the hydrant. Once this has been accomplished, they will need to connect to the hydrant's side discharge via an inline gate valve and the 3-to-5" increaser (see Appendix-B) in the plug kit. A second 5" supply line is then connected from the hydrant to the supply engine which is then pumped back to the fire ground's attack engine. You will now have the original 5" supply line that the second due laid in AND the additional 5" line that was reverse laid.
Is Plan B the optimal solution? Not really, but it's a dang good one that allows us to keep some water flowing and prevents us from having to shut down altogether.
“Plan B”
One final issue I anticipate being levied against this sort of Plan B is that the side discharge won’t supply enough water for our 5” since it is only 2.5”. I understand this concern, however, as Paul Shapiro (who is the GOAT when it comes to water supply tactics) points out,
“The 2 1/2-inch port on the hydrant can supply approximately 80 percent of what the large hydrant port can supply when using large-diameter hose.” - https://www.fireengineering.com/firefighting/did-you-know-shapiro/#gref
We need to remember that we are dealing with a pressurized system. That pressure drives massive amounts of water through these discharges and needs to be a consideration when the fire demands “big water. For example, as you can see in the chart to our right, at 50psi the side discharge of our hydrant can theoretically produce over 1,300 GPM! If we were to use a 3” supply line, we’d actually be giving up available water because the 3” can physically only handle 767 GPM. The moral of the story here is… when we have the option, go with the LDH.
Conclusion
In conclusion, where we typically run into issues that result in our Driver-Engineers saying that “we’re out of water” is when we lay more than 400’ of 5” supply hose and then expect to supply ladder pipes effectively. The friction loss on our supply hose slows the water down before it reaches our pumps, causing the intake gauge to read somewhere between 0 and 30 psi typically (depending on the initial pressure from the hydrant and other factors).
The solution is that we need to speed up our water when we anticipate the use of ladder pipes. We do this by putting an engine as close to the hydrant as possible (ideally within 100’) and pumping to our attack engines so that we overcome the friction loss in our supply hose. The engine at the hydrant should be placed in “volume mode” (if we are using multi stage pumps) and discharge a minimum 12 psi per section of 5” between them and the attack engine supplying the ladder pipe. If drivers want to keep things simple, I would start at 100-150psi. They should never exceed 190psi, as this is the working limit of most LDH we utilize. It should also be noted that most engines are equipped with pop-off valves at the intake side of our pumps that do not allow greater than roughly 190 to 210 psi, depending on the apparatus.
The issue is our water is slowing down. The solution is to speed it back up… after all, our engines are called “pumpers” NOT “suckers” for a reason. Let’s start pumping and stop sucking.
Appendix A - Functional Working Distance
The following chart provides additional information on the (theoretical) functional distance we can move water with an engine at the hydrant pumping 150psi. The Y-Axis denotes the attack pumpers compound gauge when supplied by an engine at the hydrant with a PDP of 150psi. The X-Axis denotes the distance we can effectively push water before the attack pumpers compound gauge shows 20psi.
As the above chart indicates, the maximum functional distance we can move larger volumes of water with an initial hydrant pressure of 60psi are:
1,200 GPM = 1,100 feet before we would need to place another engine in-line to achieve greater distances.
1,500 GPM = 700 feet before we would need to place another engine in-line to achieve greater distances.
2,000 GPM = 400 feet before we would need to place another engine in-line to achieve greater distances.
I want to make sure to note that there are issues that could arise due to unforeseen variables, causing all our theoretical numbers to run a foul. For example, the size of the hydrant's main and the condition of the main itself could cause volume and pressure loss to some degree. This would directly affect the working distance we could move water as modeled above. Do I anticipate this being a common issue we run into? No. But, I suppose it is possible that we find an old silver top with years of calcification and/or other damage that significantly throttles our available volume and pressure. My experience is that this is possible but not likely.
Appendix B - Heavy Hookups
“Heavy Hookups” is a term used to denote the utilization of multiple supply lines off of a SINGLE hydrant and into a SINGLE engine.
Our apparatus in are equipped with four accessible intakes:
Two, 5” Keystone
Two, 2.5” Pony Suction
By utilizing two or three hydrant discharges, we can capture the maximum amount of volume and velocity from our hydrants. The following picture details what a “heavy hookup” would look like at the hydrant.
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