Automatic sprinkler systems are generally considered one of the best ways to put out fires. Sprinklers not only make buildings safer, but they also make them look better and work better by lowering the need for certain types of fire protection and municipal water supply. One of the biggest trade-offs that code allows is that when sprinklers are put in, they can lower the amount of water needed to put out fires.

The 2024 version of NFPA 1, Fire Code, keeps the basic fire flow requirements to make sure that water supplies are good enough for firefighting, whether they are the main way to put out fires or a backup to sprinkler systems. These standards are very important for designing buildings, managing city water, and getting the fire department ready.

Establishing Fire Flow Demands in Sprinklered Structures

When sprinklers are installed, NFPA 1 says that most buildings, except for one- and two-family homes, must have a minimum fire flow of 1,000 gallons per minute (gpm). This baseline makes sure that fire departments have enough water to put out fires even when there are sprinklers, like in the following situations:

  • The sprinkler system isn’t working right.
  • There is a delay in activation.
  • The fire spread more quickly than planned.

This extra step makes sure that firefighting activities are not put at risk.

A comparison of NFPA 1’s requirements for fire flow and hydrants

The table below shows the NFPA 1 (2024) fire flow requirements for buildings that don’t have sprinklers, buildings that do have sprinklers (standard response), and buildings that do have sprinklers (rapid response). It talks about the basic fire flow requirements, the parts of NFPA 1 that are relevant, the minimum number of hydrants per Table 18.5.4.3, and important design factors.

Building Type NFPA 1 Baseline Fire Flow Requirement (gpm) Applicable NFPA 1 Section Minimum Number of Hydrants (per NFPA 1 Table 18.5.4.3) Design considerations
Non-Sprinklered Calculated per NFPA 1 often > 2,000 gpm Chapter 18, section 18.4 Based on total required flow Typically 3+ hydrants Requires largest municipal water supply and hydrant network
Sprinkelered (Standard Response) 1,000 gpm (minimum after after upto 75% reduction) Chapter 18, section 18.4.5 Based on 1,000 gpm requirement  ( number varies by hydrant capacity) Reduced water demand, but still maintains hught manual firefighting capability
Sprinklered (Quick Response) 600 gpm (minimum with AHJ Approval) Chapter 18, section 18.4.5 Exception Based on 600 gpm requirement (number varies by hydrant capacity) Lowest water deman; relies heavily on sprinkler performance and early fire control

 

Table source- https://nfsa.org/2025/08/14/understanding-nfpa-1-fire-flow-requirements/

Fire Flow Reduction and Quick Response Exception

NFPA-1 allows buildings with an approved automatic sprinkler system to reduce fire flow by up to 75%. However:

Automatic Sprinkler Systems – Even with the reduction, fire flow must be at least 1,000 gpm.

Quick‑Response Sprinkler Systems – If the building is fully protected with quick-response sprinklers in accordance with NFPA-13, the minimum permitted fire flow can be reduced to 600 gpm.

This exception is based on the better performance of quick-response sprinklers, which activate earlier in a fire’s development, reducing its size and intensity that require higher manual firefighting flows.

Requirements for hydrants and flow distribution

The NFPA 1 fire flow standards work with the rules for spacing and capacity of hydrants.

Section 18.5.4 of Chapter 18 says how many hydrants are needed based on the flow of fire.

Table 18.5.4.3 shows the most flow that one hydrant can give.

If the total fire flow needed is more than what one hydrant can handle, more hydrants must be built and placed in the right places to meet the demand. This makes sure that the fire department has enough water, no matter where the fire starts on the property.

Requirements from the Local Water Authority

NFPA 1 sets the standard, but local water utilities often have stricter rules about flow and pressure. These requirements are often based on the following:

  • The capacity of a city’s water system
  • Firefighting strategies in the area
  • Reliability of supply over time

To avoid problems during plan reviews, system acceptance, or operation, designers must make sure that their designs meet both NFPA 1 and local utility requirements.

The Role of the AHJ

The Authority Having Jurisdiction (AHJ) is the one who decides what the fire flow criteria are for a certain project. NFPA 1 gives a general guideline, but the AHJ looks at conditions that are specific to the project, such as:

  • The height, area, and type of building
  • Fire loads and dangers at work
  • Design and coverage of sprinkler systems
  • Getting to fire equipment and hoses

This flexibility lets AHJs tailor water supplies to the needs of the responding fire service and the risk level of each building.

Benefits of Sprinklers in Fire Flow Planning

The trade-offs in NFPA 1 show that automatic sprinklers can save money and make things easier to run:

  • Less water supply needed: Lower fire flows can cut down on or even eliminate the need for expensive changes to the city’s water system.
  • Sprinklers stop fires from spreading, which makes it safer for firefighters to put them out.
  • Optimised hydrant layouts: If the fire flow needs are lower, fewer hydrants may be needed.
  • Dependability in operation: Sprinklers start putting out fires quickly, which reduces the need for manual firefighting.

Conclusion

The 2024 version of NFPA 1 stresses how important it is to have a steady supply of water for firefighting, and it also talks about the proven benefits of automatic sprinkler systems. NFPA 1 links fire prevention design to the needs of municipal water systems. For example, quick-response sprinklered buildings can have flows as low as 600 gpm.

Sprinkler protection helps building owners, designers, and cities with things like planning hydrants, making sure they have enough water, and being ready to use them.

Source: National Fire Sprinkler Association (NFSA) – Fire Flow Requirements in NFPA 1 Fire Code (https://nfsa.org/2025/08/14/understanding-nfpa-1-fire-flow-requirements/)

Frequently Asked Questions (FAQs)

Q1. What does “fire flow” mean in buildings with sprinklers?

Fire flow is the least amount of water that needs to be available to support firefighting operations and the building’s sprinkler system at the same time.

Q2. Do sprinklers lower the amount of water needed for a fire?

 Yes. NFPA 1, NFPA 1142, and the IFC say that buildings with automatic sprinkler systems can often get a lower fire flow demand because sprinklers put out fires earlier.

Q3. How do you figure out the baseline fire flow?

 The size of the building, the type of construction, and the occupancy hazard classification are all used to figure out the baseline fire flow. If there are sprinklers, the flow may need to be changed.

Q4. Why are fire flow requirements important for warehouses and factories that are already built?

 Adequate fire flow means that the water supply can both feed the sprinkler system and help people fight fires by hand, which protects lives and property.