Traditional fire hose and combination nozzles operated at 100 psi and for a long time this was the standard outlined in the NFPA. This pressure supported the flow needed for interior firefighting and helped the hose resist kinking. Growing interest in lower nozzle reactions led to the development of 50 psi and 75 psi combination nozzles. As departments adopted these options, or the smooth-bore approach used by departments such as the FDNY, demand increased for hose designed to perform reliably at lower pressures. Today, fire attack packages generally follow one of two approaches: low-pressure hose-and-nozzle systems or traditional systems using 100 psi nozzle pressure.
The short answer
50 to 75 psi: Low pressure
Pros
- Lower nozzle reaction.
- More pressure available to overcome friction loss and elevation.
- Commonly used for solid bores.
Tradeoffs
- Conventional attack hose may be more prone to kinking at lower operating pressures.
- Less reach at equal flows.
- Purpose-built low-pressure hose can cost more.
100 psi: High pressure
Pros
- Most commonly used across North America.
- Hose tends to stay firmer and resist kinking.
- More reach when comparing nozzles at equal flows.
Tradeoffs
- Higher nozzle reaction.
- Not the operating range typically used for solid bores.
Standardize the complete hose-and-nozzle package. Do not mix low- and high-pressure systems in the same operating setup. This increases complexity for pump operators and can potentially lead to kinks or improperly pressurized nozzles, which affects stream quality.
1. Choose the pressure
Where lower nozzle pressure earns its keep
Every psi the nozzle does not require leaves more discharge pressure available elsewhere in the line. That matters most when elevation or distance consumes pressure before water reaches the tip.
High-rises
Elevation reduces the pressure by about 0.434 psi for every vertical foot before water reaches the nozzle. In a typical high-rise, the building has emergency pumps that increase the pressure within the standpipe. In the rare scenario where a high-rise pump is non-functional, then a lower pressure setup can allow the truck to pump higher in elevation.
Long lays beyond the pump
Friction loss compounds with distance, although larger-diameter supply hose can be used to mitigate the loss and should be the primary consideration.
Uphill pumping
Larger hose reduces friction loss, but it cannot eliminate the pressure required to overcome gravity. If you anticipate that your department may need to pump up a mountain frequently, then using a solid bore with a stiff hose may be a good option.
Smaller crews
Lower nozzle pressure reduces reaction at the same flow and can make the line easier to handle.
2. Choose the stream
Solid bore or fog?
Nozzle pressure and stream choice are related, but they are not the same decision. The right question is which stream characteristics you require.
Solid bore: Simple, predictable, and efficient
Some departments prefer solid bores for their simple, repeatable stream. The open waterway has few moving parts, passes debris readily, but has no adjustable fog pattern.
- High flow at low nozzle pressure.
- Large droplets with strong effective reach and penetration.
- Less affected by wind, with water landing in a concentrated area.
- No accidental change to a wide fog pattern indoors.
Tradeoff: Its simplicity also limits your options. A fixed solid-bore tip has no selectable flow or adjustable pattern.
Fog nozzle: More pattern choices
A combination nozzle can produce a straight stream, narrow fog, or wide fog. That flexibility gives crews capabilities a fixed solid bore does not provide.
- Narrow fog supports hydraulic ventilation through an opening.
- A wide pattern can protect against radiant heat during emergency withdrawal.
- Available in fixed, selectable, and automatic designs.
Tradeoff: More expensive and requires more maintenance.
3. Match the hose
The hose and nozzle are one system.
The nozzle sets the pressure requirement. The hose must remain firm enough to resist kinking at that pressure.
High-pressure attack hose is designed to run firm near 100 psi. At lower operating pressures, some lightweight hose can bend and kink more easily.
- Check stability: Test kink resistance at the pressure and flow your department intends to use.
- Compare construction: More structural support or a thicker liner may help hose remain firm at reduced pressure.
- Consider handling: Low-pressure hose may be heavier and less flexible, which can make it harder to stack neatly in preconnected hose beds.
4. Train with your equipment
Train for different nozzle pressures. Work smarter, not harder.
Good training helps crews work effectively with either package, but equipment selection still affects flow, reaction, and hose handling. Departments all over the country are using various setups and are successfully putting out fires daily. Lower nozzle reaction helps, but good technique determines how effectively a crew can control and advance the line. Body position, pinning the hose with a knee, and using a coil for larger lines allow crews to work with nozzle reaction instead of fighting it.
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