1. Automatic sprinkler system demand
An automatic sprinkler opens on its own when its heat-activated element reaches its thermal rating, and water discharges over the area it covers (the NFPA 13 definition reproduced in NFPA 25). The pump therefore does not serve the whole building: it serves the design area, which is the area of greatest hydraulic demand in the system (IT 23, 11.1.3.1.1), at the density required by the hazard class and with the losses back to the water supply.
In São Paulo, IT 23 requires the system to be designed to Brazilian technical standards and accepts NFPA 13 where they do not cover the subject, but the design area, tables and other parameters follow the IT itself (4.1); storage buildings go to IT 24 (2.3). The hazard class comes from the IT 14 fire load, as the table in this section shows (2.4).
Where adjacent occupancies are not separated by barriers able to hold back the heat for some time, the system of the occupancy with the greater demand extends 4.5 m beyond its perimeter (10.2).
Sizing is by hydraulic calculation (10.1). Pipe schedule tables apply only to new systems under 465 m² or to extensions of systems originally sized by them (11.2.1.1), and never to sprinklers with a nominal K-factor other than 80 or in extra hazard areas, groups 1 and 2 (11.2.1.2).
In the density/area method, one point of the selected curve is enough (10.4.4.1); if the design area is under 140 m² in light or ordinary hazard, or under 230 m² in extra hazard, the density for those areas is used (10.4.3). The area is rectangular, with the side parallel to the branch lines at least 1.2 times the square root of the design area (11.1.3.2.1).
No sprinkler operates below 48 kPa (4.8 m of water column) unless specific tests recommend more (11.1.3.9), and in extra hazard none exceeds 1,210 kPa (123.5 m of water column) (11.1.3.10). Each sprinkler’s flow comes from its K-factor through K = Q/√p, the same relation used to balance branch lines (11.1.2.3), with a 1 kPa (0.1 m of water column) tolerance at hydraulic junction points (11.1.2.1).
That is why there is no single sprinkler pressure: the pressure asked of the pump results from the pressure at the hydraulically most demanding sprinkler, the losses along the way and the elevation difference, less the pressure available at suction.
The reserve uses the duration in Table 11 (10.4.1.4); in a mixed occupancy, it takes the flow of the most severe hazard with the duration of the predominant hazard (4.5). The alarm is activated by a flow equivalent to that of one sprinkler with the smallest orifice, sounds within 2 minutes and is identified at the panel (5.1); in a wet pipe system, it comes from an alarm check valve or another flow detector (5.2).
Pumps follow IT 22 Annex C and NBR 16704 (7.5), with mandatory positive suction pressure and no priming tank (7.5.1), protected against mechanical damage, weather, chemical agents, fire or humidity (12). In Goiás, NT 23 repeats positive suction pressure with no priming tank (5.18), refers to NT 22 Annex C and NBR 16704 (5.17) and adopts NBR 10897 on matters it does not detail (2.2).
| Hazard class | Fire load (IT 14) | Reserve duration | Minimum area for the density |
|---|---|---|---|
| Light | Up to 300 MJ/m² | 30 min | 140 m² |
| Ordinary, Group I | Above 300 up to 800 MJ/m² | 60 min | 140 m² |
| Ordinary, Group II | Above 800 up to 1,200 MJ/m² | 60 min | 140 m² |
| Extra, Group I | Above 1,200 MJ/m², with no ignitable liquids | 90 min | 230 m² |
| Extra, Group II | Moderate or substantial quantities of combustible or flammable liquids (M-2 in IT 14) | 90 min | 230 m² |
2. Hydrant and hose reel network demand
NBR 13714 distinguishes two outlet types. The hydrant is a water outlet point with one (single) or two (double) outlets, with angle valves, adapters, caps, fire hoses and accessories (3.8); the hose reel (mangotinho) has a single outlet with a quick-opening valve, a semi-rigid hose and an adjustable nozzle (3.12). In the standard, hose reels make up type 1 systems and hydrants types 2 and 3, and the reserve exists for first-response firefighting until the fire department takes over (5.4.1).
In São Paulo, IT 22 has five system types: type 1 is the hose reel, and types 2 to 5 are hydrants. Table 2 sets the minimum flow and pressure at the valve of the most unfavorable hydrant, measured at the valve outlet (4.6.1.2).
The calculation assumes simultaneous use of the two most unfavorable jets (4.8.3); if the two most unfavorable outlets belong to one double hydrant, those two points are used (4.8.3.1), and the most unfavorable is the one with the lowest dynamic pressure at the hydrant outlet (4.8.4).
Lower nozzle pressures are accepted when hydraulic calculation and manufacturers’ catalogs prove the table flow and the jet reach (Table 2, note 2), and the designer may carry out the full calculation, with all losses, starting from the table flows and the pressure needed for the jet to reach 10 m with the nozzle at up to 1.20 m above the floor (4.8.9).
Pressure and velocity limits feed into selection. Under IT 22, working pressure at the nozzles does not exceed 100 m of water column (1,000 kPa) (4.8.8); pump suction velocity stays within 2 m/s with negative suction and 3 m/s with positive suction (4.8.11), and pipe velocity within 5 m/s (4.8.12); at the branch point toward the two most unfavorable hydrants, a variation of up to 0.50 m of water column is allowed (4.8.14).
With negative suction, available NPSH is calculated at 1.5 times the system’s rated flow and must be equal to or greater than the pump’s required NPSH (4.8.15). NBR 13714, in turn, limits the dynamic pressure at any nozzle to twice that at the most unfavorable one (5.3.6), recommends no more than 1,000 kPa at any point (5.3.7) and limits suction velocity to 4 m/s (5.3.9).
Under NBR 13714, the minimum reserve is V = Q × t, with Q equal to the flow of two outlets and t of 60 minutes for types 1 and 2 and 30 minutes for type 3 (5.4.2). In São Paulo, the system type and minimum volume come from IT 22 Table 3, by occupancy (4.9.1 and 4.12.3).
In a mixed-occupancy building with a single system, the reserve considers the total area and the predominant hazard (4.8.5.2.1), and the pump meets the highest pressure and flow values of the two most unfavorable hydrants of each occupancy (4.8.5.2.3); independent systems apply only to single-storey buildings with the occupancies compartmented (4.8.5.1 and Chart 1).
| Type | Nozzle and hose DN | Outlets | Minimum flow (L/min) | Minimum pressure (m of water column) |
|---|---|---|---|---|
| 1 (hose reel) | 25 | Single | 100 | 80 |
| 2 | 40 | Single | 150 | 30 |
| 3 | 40 | Single | 200 | 40 |
| 4 | 40 | Single | 300 | 65 |
| 4 | 65 | Single | 300 | 30 |
| 5 | 65 | Double | 600 | 60 |
Note
IT 22 types 1 to 5 are not NBR 13714 types 1 to 3, and a state instruction’s rule is not an identical requirement throughout Brazil: check which document the design adopts before comparing flows.
3. Deluge: every nozzle on the valve at once
In a deluge system, the sprinklers or nozzles are open and connect to the water supply through a valve that opens only when the detection system installed in the same area operates. Once the valve opens, water flows into the piping and discharges through every sprinkler or nozzle attached to it (the NFPA 13 definition reproduced in NFPA 25). The NFPA 25 annex states that each deluge valve is intended to be capable of automatic and manual operation.
That is why deluge demand is not a design area chosen within the network: it is the sum of the flows of every nozzle on the valve that opens, each given by the K-factor at that nozzle’s pressure, and the pressure asked of the pump covers the most unfavorable nozzle and the losses to it. If the design has more than one valve opening in the same event, the report must show that sum.
Under IT 23, losses or equivalent lengths of deluge valves come from the manufacturer or, failing that, from applicable technical literature (11.1.2.4), and water curtain demand is added to the ceiling sprinkler demand at the connection point, balanced to the higher pressure (10.4.3).
Under IT 23, preaction and deluge systems have two independently actuated alarms, one by the detection system and the other by water flow (5.3). A deluge system needs no test connection (5.11), whereas a preaction system has one, using the supervisory air (5.10).
To quote the pump, send the report with the list of nozzles per valve and their K-factors, the pressure required at the most unfavorable nozzle, the deluge valve loss stated by the manufacturer, the detection and control logic, and the suction and reserve conditions. The curve is chosen for that duty point, not from a flow range by industry type.
4. Stairwell pressurization uses air
Stairwell pressurization keeps the escape stair free of smoke so occupants can evacuate, and it can also be activated in any evacuation of the building (Goiás NT 13, 1.2). The space is pressurized by a continuous air supply that maintains a pressure differential to the adjacent spaces and a flow through escape paths to the outside (5.1.1). The basic elements are the actuation and alarm system, mechanically supplied outdoor air, the air escape path and a guaranteed power source (5.1.3).
The numbers are for air, not water. The design level is not below NT 13 Table A1 and does not exceed 60 Pa with all fire doors closed (5.1.5.1), and the minimum calculation differential is 50 Pa (5.1.6.1). With a permanent opening in the stair enclosure, the airflow must give an average velocity of 4 m/s through that opening, and, with doors open during evacuation, at least 1.0 m/s leaving through them (5.1.6.4).
The NT recommends a two-stage system, with a low continuous level and a higher one in an emergency (5.1.2); in buildings with several pressurized stairs, it requires an independent system for each (5.2.2); and, where there are two fan sets, one backing up the other, it requires an automatic device that detects one stopping and starts the other (5.3.9).
The point of contact with the fire pump is power. The building has an automated generator set with at least 4 hours of autonomy (5.3.8 b), which may also supply the other emergency systems, among them what the NT calls hydraulic fire pressurization pumps (5.3.8 c); the fan starts from automatic smoke detection (5.3.8 d). If the generator is shared, give the electrical designer the pump’s power and starting method.
The name is confusing: a jockey pump is also called a pressure-maintenance pump, but it keeps the water network pressurized and moves no air. Keep designs and controls identified by function; building coordination handles the interfaces without mixing the equipment.
5. How to compare demands and integrate the networks
The table summarizes what changes between the three systems under the rules cited on this page. Final flows and pressures always come from the design report.
In São Paulo, integration starts from two rules: IT 23 adds the hydrant demand to the sprinkler demand in the hydraulic calculation and in sizing the reserve (10.4.1.1), and IT 22 allows the reserve to supply other manual or automatic protection systems through interconnection of the reservoir piping, provided the IT 23 parameters are met (4.9.2). Under NBR 13714, such interconnection is not allowed, except for type 1 systems, the hose reel systems, with properly sized automatic sprinklers (5.4.3).
In Goiás, with hydrants and hose reels installed together with automatic sprinklers, NT 23 requires the NT 22 minimum flows and pressures to be guaranteed and the effective reserves to be added (5.8).
The hydrant branch is taken upstream of the sprinkler alarm check valves (5.8 a); exceptionally, a single combustion-engine pump serves both systems, provided there is a backup starting method from stationary batteries, activated automatically if the main one fails (5.8 b); and a single double fire department connection supplies both systems at once (5.8 c).
For a common pump, the curve must cover the combined scenario point where the rule adds demands and the highest point of each system where it does not, as in the IT 22 single hydrant system for mixed occupancies, which meets the highest pressure and flow values with no simultaneity of events (4.12.4). With separate pumps, each has its own duty point, and the reserve and suction follow the applicable summing rule.
The choice between a common pump and separate pumps belongs to the design, not to a one-pump-per-system-name rule.
| Criterion | Automatic sprinklers | Hydrants and hose reels | Deluge |
|---|---|---|---|
| Actuation | Each sprinkler opens by heat at its element | Manual, by the fire brigade or fire department | Detection opens the valve; manual operation is also provided |
| Design scenario | Design area of greatest demand (IT 23, 11.1.3.1.1) | Two most unfavorable jets at once (IT 22, 4.8.3; NBR 13714, 5.3.3) | Every nozzle on the valve that opens |
| Reference pressure | At least 48 kPa per sprinkler; at most 1,210 kPa in extra hazard (IT 23) | IT 22 Table 2 at the valve; up to 100 m of water column at the nozzle | Pressure required at the most unfavorable nozzle, per the report |
| Reserve duration | 30, 60 or 90 min by class (IT 23, Table 11) | IT 22 Table 3; NBR 13714: 60 min for types 1 and 2 and 30 min for type 3 | Per the criterion adopted in the design |
| Integration in SP | Adds the hydrant demand (IT 23, 10.4.1.1) | IT 22 Table 2 even with independent networks (IT 23, 10.4.1.2) | Per the system report |
| Integration in GO | Hydrants branched upstream of the alarm check valve (NT 23, 5.8 a) | NT 22 flows and pressures; effective reserves added (NT 23, 5.8) | Per the system report |
6. Testing, maintenance and changes
Where the contract adopts NFPA 25, each system has its own summary table for inspection, testing and maintenance: automatic sprinklers, standpipe and hose systems, private fire service mains with their hydrants, fire pumps and valves. Pump frequencies do not apply to sprinklers or hydrants, and the maintenance plan follows each system’s table.
For the pump, the no-flow test is weekly for a diesel and monthly for most electric pumps, which go back to weekly in cases such as suction from a ground-level tank, unless a redundant pump is provided; the start is automatic and the pump runs for at least 10 minutes if electric or 30 if diesel.
The flow test is annual, and the result is acceptable, among other conditions, when the pump meets the flow and pressure of the most demanding system it supplies, based on owner-provided design information, supplies 100% of rated flow and delivers, at each flow point, a net pressure of at least 95% of that shown on one of the reference curves: the original manufacturer’s curve, the original unadjusted field test curve or the curve generated from the pump nameplate.
In São Paulo, IT 23 recommends that the responsible professional fill in the Annex B commissioning report after installation and the Annex C inspection report when the inspection certificate is renewed, signed by the owner or occupant (13). The inspection report asks whether the pump performance curve prepared by the manufacturer before installation was presented, and a curve produced in the last 36 months (Annex C, 4.2 and 4.3).
IT 23 also requires a stock of spare sprinklers for immediate replacement, with the same characteristics as those installed and kept where the temperature does not exceed 38 °C: at least 6 in installations with up to 300 sprinklers, 12 from 301 to 1,000 and 24 above 1,000, with at least four of each type, model and temperature rating where there is more than one (9.1 to 9.3).
A change of occupancy, hazard class, storage, protected area, network or reserve changes the demand. Redo the calculation before accepting the existing pump, record the actual configuration and keep the acceptance and maintenance results.
Engineering note
The frequencies and durations cited here are NFPA 25’s for the pump and apply when the contract adopts it; those for sprinklers, hydrants and valves are in each system’s summary table and go into the maintenance plan.