IFC Fire Hydrants and Water Supply
Summary
The IFC requires an approved water supply that can deliver the fire flow a building needs, and fire hydrants within set distances of the building and along access roads. Fire flow depends on building area, construction type, and sprinklers, so it fixes the size of the water service and the hydrant layout early in site design.
Cols
Scope
- Cites the 2024 IFC, Section 507 and Appendices B and C. Always verify the adopted code edition and local amendments for the project jurisdiction
- Appendices B and C apply only where the adopting ordinance references them; the water utility and fire department often set their own fire flow and hydrant rules
- Sprinkler and standpipe system design is in NFPA 13, 14, and 24 and the IBC fire protection note
- Domestic water service sizing and backflow preventers are plumbing design items coordinated with fire flow
Terminology
- Fire flow: the water flow rate, in gallons per minute (gpm), needed to fight a fire in a building for a set duration
- Fire-flow calculation area: the building area used to find fire flow
- Residual pressure: the pressure left in the water system while the fire flow is delivered (20 psi in the appendix table)
- Fire hydrant: a street or site connection from which the fire department draws water
- Private fire service main: an on-site underground pipe supplying hydrants or sprinkler systems
- Fire department connection (FDC): the inlet where the fire department supplies a sprinkler or standpipe system
- Water supply test (flow test): a measured test of available flow and pressure at a hydrant
- Average spacing: the average distance between hydrants along a street
- Water purveyor: the utility that supplies the water
- Dead-end main: a water main with water coming from one direction only
Requirements
Water supply and fire flow
- IFC 2024, Section 507.1: an approved water supply capable of supplying the required fire flow is provided for new or relocated buildings
- IFC 2024, Section 507.2: supplies can be reservoirs, pressure tanks, elevated tanks, water mains, or other fixed systems; private fire service mains follow NFPA 24 and private tanks follow NFPA 22
- IFC 2024, Section 507.3: fire flow is determined by an approved method or by Appendix B
- IFC 2024, Section 507.4: the fire code official is notified before the water supply test and either witnesses it or receives approved documentation before final approval
Fire flow (Appendix B)
- IFC 2024, Table B105.1(1): one- and two-family dwellings, R-3, R-4, and townhouses
| Fire-flow calculation area (sq ft) | Sprinklers | Minimum fire flow (gpm) | Duration (hours) |
|---|---|---|---|
| 0 to 3,600 | None | 1,000 | 1 |
| 3,601 and greater | None | Table B105.1(2) value | Table B105.1(2) duration |
| 0 to 3,600 | NFPA 13D system | 500 | 1/2 |
| 3,601 and greater | NFPA 13D system | 1/2 of the Table B105.1(2) value | 1 |
- IFC 2024, Section B105.2: other buildings take the Table B105.1(2) value without sprinklers; with an NFPA 13 system (Section 903.3.1.1), 25 percent of the table value but not less than 1,000 gpm; with an NFPA 13R system (Section 903.3.1.2), 25 percent but not less than 1,500 gpm
- IFC 2024, Section B105.3: for a sprinklered building the water supply is the greater of the sprinkler system demand with hose stream allowance and the required fire flow
- IFC 2024, Table B105.1(2): fire flow by calculation area and construction type, measured at 20 psi residual pressure; selected rows
| Fire flow (gpm) | Types II-B and III-B (sq ft) | Type V-B (sq ft) | Type I-A and I-B (sq ft) |
|---|---|---|---|
| 1,500 | 0 to 5,900 | 0 to 3,600 | 0 to 22,700 |
| 2,000 | 7,901 to 9,800 | 4,801 to 6,200 | 30,201 to 38,700 |
| 3,000 | 18,401 to 21,800 | 11,301 to 13,400 | 70,901 to 83,700 |
| 4,000 | 33,501 to 37,900 | 20,601 to 23,300 | 128,701 to 145,900 |
Hydrants
- IFC 2024, Section 507.5.1: on-site hydrants and mains are provided where the fire code official requires them and a building or portion of it is more than 400 ft from a hydrant on an access road, measured by an approved route; 600 ft for Group R-3 and U buildings sprinklered throughout
- IFC 2024, Section 507.5.1.1: buildings with a standpipe have a hydrant within 100 ft of the fire department connection, or a greater distance the official approves
- IFC 2024, Section 507.5.4: unobstructed access to hydrants at all times
- IFC 2024, Section 507.5.5: a 3 ft clear space around the circumference of hydrants
- IFC 2024, Section 507.5.6: guard posts or other protection where vehicle impact is possible
- IFC 2024, Table C102.1: minimum hydrants and spacing by fire flow
| Fire flow (gpm) | Minimum hydrants | Average spacing (ft) | Maximum distance from any point on the street frontage (ft) |
|---|---|---|---|
| 1,750 or less | 1 | 500 | 250 |
| 1,751 to 2,250 | 2 | 450 | 225 |
| 2,251 to 2,750 | 3 | 450 | 225 |
| 2,751 to 3,250 | 3 | 400 | 225 |
| 3,251 to 4,000 | 4 | 350 | 210 |
| 4,001 to 5,000 | 5 | 300 | 180 |
| 5,001 to 5,500 | 6 | 300 | 180 |
| 5,501 to 6,000 | 6 | 250 | 150 |
| 6,001 to 7,000 | 7 | 250 | 150 |
| 7,001 or more | 8, plus 1 per 1,000 gpm over 7,000 | 200 | 120 |
- IFC 2024, Table C102.1 notes: spacing is reduced by 100 ft and the maximum distance by 50 ft on dead-end streets; spacing may increase by 50 percent for buildings sprinklered under Section 903.3.1.1 and 25 percent under Sections 903.3.1.2 or 903.3.1.3; the fire code official may modify location, number, and distribution
- IFC 2024, Section C103.2: average spacing may increase by 10 percent where existing hydrants provide all or part of the required number
Worked examples
Warehouse fire flow
A Type II-B warehouse of 30,000 sq ft, sprinklered with an NFPA 13 system (Group S-1).
| Step | Source | Result |
|---|---|---|
| Fire-flow calculation area | 30,000 sq ft | Used as given |
| Unreduced fire flow | Table B105.1(2), Type II-B, 29,301 to 33,500 | 3,750 gpm for 3 hours |
| Sprinkler reduction | 25 percent of 3,750 | 937 gpm, but not less than 1,000 |
| Required fire flow | Greater of the two | 1,000 gpm |
| Water supply | Greater of the sprinkler demand with hose stream and 1,000 gpm | Set by the sprinkler design |
Hydrants for a 3,000 gpm requirement
| Step | Source | Result |
|---|---|---|
| Fire flow | 3,000 gpm | Row 2,751 to 3,250 gpm |
| Minimum hydrants | Table C102.1 | 3 |
| Average spacing | 400 ft | Hydrants about 400 ft apart |
| Maximum distance from any frontage point | 225 ft | No point on the street frontage more than 225 ft away |
| Sprinklered building NFPA 13 | Spacing up by 50 percent | About 600 ft spacing, if the official allows |
House fire flow
A 2,800 sq ft house with an NFPA 13D system.
| Step | Source | Result |
|---|---|---|
| Calculation area | 2,800 sq ft, under 3,601 | Small-house row |
| Fire flow with 13D | Table B105.1(1) | 500 gpm for 1/2 hour |
| Unsprinklered comparison | Same row | 1,000 gpm for 1 hour |
Coordination
- Water purveyor: request a hydrant flow test early; the available flow and pressure decide whether a fire pump or tank is needed
- Civil engineering: private mains, hydrants, and fire department connections are placed on the site plan with the access road
- Fire department: confirm hydrant type, connection thread, and location preferences
- Plumbing: fire service and domestic service sizes, backflow preventers, and meter vaults take space near the building entry
- Sprinkler designer: the hose stream allowance and the demand set the system requirements; the lower of the supply and demand governs design
- Site layout: hydrants need a 3 ft clear space, protection from vehicles, and access from the road
Common issues
- Fire flow unknown late: a weak water main discovered at plan review forces a pump or tank
- Construction type affects flow: a lower construction type raises the fire-flow area band
- Sprinkler reduction misread: the reduction cannot drop the flow below the stated minimum
- Hydrant behind a fence: hydrants must be reachable without barriers
- Dead-end mains: spacing and flow are limited, and the official may require looping
- FDC far from a hydrant: more than 100 ft from the connection
Standards
- NFPA 24: installation of private fire service mains and their appurtenances
- NFPA 22: water tanks for private fire protection
- NFPA 13, 13R, 13D: sprinkler system design standards that set demand
Sources
- GoCodebook: 2025 California Fire Code, Section 507 fire protection water supplies (based on the 2024 IFC), https://gocodebook.com/library/us/ca/ca-fire-code/chapter-5-fire-service-features/section-507-fire-protection-water-supplies
- GoCodebook: 2025 California Fire Code, Appendix B, Section B105 fire-flow requirements, https://gocodebook.com/library/us/ca/ca-fire-code/appendix-b-fire-flow-requirements-for-buildings/section-b105-fire-flow-requirements-for-buildings
- GoCodebook: 2025 California Fire Code, Appendix C, Section C102 number of fire hydrants, https://gocodebook.com/library/us/ca/ca-fire-code/appendix-c-fire-hydrant-locations-and-distribution/section-c102-number-of-fire-hydrants
- GoCodebook: 2025 California Fire Code, Appendix C, Section C103 fire hydrant spacing, https://gocodebook.com/library/us/ca/ca-fire-code/appendix-c-fire-hydrant-locations-and-distribution/section-c103-fire-hydrant-spacing