How to Choose Your Firefighting Nozzle and Hose

During a hose and nozzle demonstration, you have one goal: find the right solution for your fire department.

You can expect your sales rep to guide you through the selection process with expert insight and advice. Everyone will conduct their demonstration a little bit differently, but in general, they should all start with the nozzle.

In this article, we’ll walk you through the process of choosing a nozzle, a few considerations for pairing with hose, and how to figure out the Pump Discharge Pressure (PDP).

Start with the Nozzle 

First, your sales rep will guide you through choosing a nozzle based on basic criteria that takes your needs and goals into account. Hoses should be selected after the nozzle based on nozzle flow and pressure rating.

Nozzle Selection Criteria: 

  • Intended Application
  • Desired Flow (GPM)
  • Desired Nozzle Pressure (PSI)
  • Need for variable or fixed gallonage nozzle
  • Smooth bore or combination nozzle

Let’s look at each of these fire nozzle criteria more fully.

Intended Firefighting Nozzle Application 

Your nozzle should be selected based on the intended application. Structural firefighting nozzles for pre-connected lines are most common. However, you may have other needs, such as high-rise, foam operations, or extended line applications. Each of these scenarios may require different flow rates or pattern capabilities that must be considered.

For example, if the intended use of the nozzle includes use with a foam eductor, a high flow/low-pressure fixed gallonage nozzle may not be the ideal choice. A smooth bore would also be a poor choice due to their inability to agitate your foam solution properly. Instead, you would want to consider an automatic, selectable, or fixed gallonage nozzle with a flow rating that includes or matches the flow rate of the eductor.

Desired Flow 

You will select the flow rate of your nozzle based on a couple of factors:

  1. NFPA 1710 application rates for specific application scenarios
  2. Matching the nozzle to a foam eductor or existing nozzles being used by the department

Knowing your desired flow rate narrows the nozzle choices down to the correct body size.

  • Small Body: Flows of 100 GPM and lower
  • Mid-Range Body: Flows up to 200 GPM
  • Large Body: Flows up to 300+ GPM

Desired Nozzle Pressure 

Your desired nozzle pressure is based on several factors. The most prominent factor is nozzle reaction. The lower the nozzle pressure is at a given flow, the less the nozzle reaction will be. Lower nozzle reaction allows for greater mobility and less work on the nozzle operator.

You should also consider what hose you plan to use and what pump pressure or standpipe pressures you will have available to you.

It is at this point that hose becomes an even more key factor. If you are not buying hose, you need to be mindful of your current hose and understand that the kink resistance may not be ideal for 75 PSI and 50 PSI nozzles or smooth bores. Kinking or bad handling characteristics at the nozzle can be an issue if this is not considered.

Sometimes, you may end up disliking a nozzle not due to its performance, but because it has poor handling characteristics based on incompatible hose pairings.

If your department is buying both hose and nozzles at the same time, you have a clean canvas to work with and can choose an ideal hose and nozzle package based on your criteria.

Need for Variable or Fixed Gallonage 

Deciding whether you need a variable or fixed gallonage nozzle depends on the flow requirements for your intended application(s). If your nozzle needs to flow 150 GPM for interior firefighting and 95 GPM for use with a foam eductor, variable flow (selectable GPM or an automatic) is a desirable choice.

If the nozzle is intended for interior use only without a wide flow variation, or to be paired exclusively with an eductor, then an appropriate fixed gallonage nozzle will suffice.

Fixed gallonage nozzles can be utilized at various flows, but the coinciding change in nozzle pressure should be considered.

Smooth Bore Nozzle or Combination Nozzle 

There are many reasons for choosing smooth bore nozzles or combination nozzles. You can choose whichever nozzle type you prefer, though you need to be mindful of flow rates and your intended application.

Pairing Fire Hose and Nozzles 

After deciding the nozzle that best meets your needs, you can move on to the hose choice. The most important aspect of pairing hose and nozzles is kink resistance with low-pressure nozzles.

Most hose vendors offer multiple choices to accommodate this need along with an internal diameter that meets the needs of your desired flow. Simply put, do not carry more water than you need for the desired flow and make sure there is kink resistance to sustain the line at low pressures. This helps prevent kinks and ensure good handling characteristics at the nozzle end.

With nozzles that operate at higher pressures (75PSI or 100PSI) kink resistance is of less importance. In these cases, other hose models may be suitable. You can still use the premium kink resistant options if desired, but you should defer to your hose supplier for their recommendation based on the selected nozzle’s flow and operating pressure. Your hose supplier will be the authority on their product line and make the best recommendations.

Finding Pump Discharge Pressure 

During your nozzle and hose demo, you will need to find your Pump Discharge Pressure for your desired flow. Pump Discharge Pressure (PDP) is determined based on nozzle pressure (NP) and hose friction loss (FL).

Friction loss can include devices or plumbing, but those need to be adjusted for or added to the results of the formula afterwards and only if applicable.

There are several smart phone apps or slide charts that help you arrive at the correct answer, but PDP can also be figured out using your phone calculator.

PDP = NP + FL 

  • Your nozzle pressure is either 50, 75, or 100
  • For this example, we use 75
  • Friction loss is based on flow, hose coefficient, and hose length
  • The coefficient is provided by the hose manufacturer
  • The sum of these numbers is your PDP

Let us find the PDP for a 150 GPM nozzle at 75 PSI on 200’ of 1.75” hose with a coefficient of 10.

PDP = 75 + FL

Now, we need to figure out friction loss and add that to the nozzle pressure. Friction loss has its own formula.

FL = Friction Loss Coefficient * (flow rate/ 100)2  * hose length/100 

Our desired flow in this example is 150 GPM. The friction loss coefficient we were provided with is 10. We have 200 feet of hose.

With the numbers filled in, our formula would look like this:

FL = 10 * (150/100)2 * 200/100

We would solve the formula using the following steps:

  • 10 * (1.5)2 * 2
  • 10 * 2.25 * 2
  • FL = 45

Now, we need to add the friction loss of 45 PSI into our PDP formula from earlier.

  • PDP = 75 + FL
  • PDP = 75 + 45
  • PDP = 120 PSI

Knowing what the PDP should be is a starting point and sometimes needs to be adjusted up or down based on actual losses in plumbing or hose. You can simplify this step during a demo, testing, and training with a water flow meter. If you are not comfortable figuring out friction loss or PDP, a water flow meter will allow you to stretch the hose and throttle up to the desired GPM without working the formulas first.

The TFT SHO-FLOW app has a PDP calculator that allows you to select the flow rate, nozzle pressure, hose size or coefficient, and hose length. It then calculates PDP for you. 

Once at the desired GPM, you can explore features and evaluate the handling and performance characteristics of both the hose and nozzle.