The sprinkler is the most common and most misunderstood system of automatic fire suppression. Each head contains a glass bulb filled with liquid that plugs the pipe; the heat of the fire bursts the bulb, only that head releasing water. BYKHY mandates sprinklers in many structures, particularly in high-rise buildings.
How Sprinklers Work
A sprinkler system consists of a piping network maintained under constant pressure and heads connected to this network. Each head contains a liquid-filled, heat-sensitive glass bulb (or fusible link) that physically blocks water discharge.
The heat from the fire warms the bulb, the liquid inside expands, and the bulb bursts. The plug is removed, pressurized water flows out, and the deflector plate beneath the head distributes water over the fire.
Critical point: This is entirely mechanical and localized. The panel cannot open a head; smoke cannot open a head; an alarm cannot open a head. For a head to open, there must be fire heat directly beneath that specific head. This is why only 1–2 heads operate in a typical fire, and water damage remains limited to the fire itself.
The panel's role is limited: a flow switch in the line signals "water is flowing," the panel sounds an alarm and starts the pump.
Bulb Temperature Classes
The bulb color indicates the burst temperature. Temperature is selected at approximately 30 °C above the location's normal maximum temperature — otherwise the head will open spontaneously in summer heat or in a boiler room.
| Bulb color | Temperature | Typical location |
|---|---|---|
| Orange | 57 °C | Cold locations |
| Red | 68 °C | Most common — offices, corridors, parking lots, shops |
| Yellow | 79 °C | Hot locations |
| Green | 93 °C | Near kitchens, attics |
| Blue | 141 °C | Boiler rooms, oven surrounds |
System Types: Wet, Dry, Pre-Action, Deluge
| Typical use | What is in the pipe | Where | Note |
|---|---|---|---|
| Wet pipe | Water (pressurized) | All heated locations — offices, hotels, shopping centers, hospitals | Simplest, fastest, most common |
| Dry pipe | Pressurized air; water arrives when head opens | Locations with freezing risk — parking lots, cold storage, open storage | Water arrives with a few seconds delay |
| Pre-action | Air; for water both detector and bulb are required | Data centers, archives, museums — locations where accidental water is unwanted | Dual lock: an accidentally broken head does not release water |
| Deluge | Empty; heads are bulbless/open | Tank farms, transformers, rapid-spread fire risk | When triggered, all heads release water simultaneously |
Attention: "All open at once" is true only for deluge systems — and there it is a deliberate design choice, because flammable liquid fires spread across the entire area in seconds. Normal sprinkler systems do not exhibit such behavior.
Why Pre-Action Systems Exist
In locations like data centers, there are two fears: fire and accidental water. In a pre-action system, the pipe contains no water; water fills the pipe only if the detector triggers and the bulb also bursts before water flows out. If a forklift accidentally breaks a head, no water flows — because the detector has not alarmed.
Hazard Classification and Water Discharge Rate
The heart of sprinkler design is not head count, but hydraulic calculation. The location is classified by hazard based on fire load, and for each class, the required water density (mm/min) and the assumed simultaneous coverage area are determined:
- LH — Light Hazard: schools, offices, hospital rooms. Low fire load.
- OH — Ordinary Hazard: parking lots, shops, restaurants, manufacturing. Most commercial buildings fall here.
- HH — High Hazard: high-bay storage, plastic/rubber storage, flammable liquids. Highest discharge rate.
In storage facilities, also storage height and rack type directly affect calculations; ceiling heads alone are insufficient for high racks, in-rack heads may be required.
The practical consequence: If a facility's use changes (office → warehouse, warehouse → plastic storage), the existing sprinkler system becomes inadequate. Simply saying "the system already exists" is not sufficient; calculations must be redone for the new fire load.
Fire Pump and Water Tank
A sprinkler system is only as good as the water source behind it. The city water supply alone is not considered adequate; the system requires:
- Fire water tank — with sufficient capacity to deliver the calculated discharge for the calculated duration
- Main pump (electric) + backup pump (diesel) — the system must continue operating if power fails
- Jockey pump — compensates for minor leaks and maintains pressure in the network; prevents unnecessary operation of the main pump
A "sprinkler system" without pump room and storage tank is merely piping that delivers water for a few minutes during a fire and then runs dry.
Common Field Mistakes
- Distributing heads without hydraulic calculation — the most common and costliest mistake
- Installing a wet system in a parking lot — pipes freeze and burst; a dry system is required there
- Wrong bulb temperature — installing 68 °C heads in a boiler room causes spontaneous opening
- Blocking the head's face — suspended ceilings, ducts, shelves, or curtains prevent the deflector from distributing water; the head opens but water does not reach the fire
- Failing to update calculations when use changes — a system calculated for office use becomes insufficient when converted to storage
- Failing to monitor valves — a closed main valve disables the entire system; valves must be connected to the panel with supervisory switches
- Neglecting pump tests — if the diesel pump does not work, there is no system during a power outage
Regulations
Sprinkler systems BYKHY requires this; design and calculations must be performed to wheeled devices must have (and NFPA 13 as per design) standards. Which buildings fall within scope is explained threshold by threshold on the sprinkler mandatory locations page. Documents required at acceptance: hydraulic calculation report, pump performance test, and flow test records.
Frequently Asked Questions
Do all sprinklers open at once when the alarm sounds?
No. This is the most common misconception in this sector. Each head opens with its own bulb, only by the fire heat beneath it; the panel, smoke, or alarm cannot open a head. In a typical fire, 1–2 heads operate. The "all at once" behavior exists only in deluge systems and is for special locations such as tank farms.
Can a sprinkler accidentally activate and flood the building with water?
The bulb requires actual fire heat to burst. The risk is physical damage to the head (e.g., forklift impact) — for this, a protective cage is used. Where accidental water is unacceptable (data center, archive), a pre-action system is installed: there is no water in the pipe; the pipe does not fill with water until the detector gives an alarm.
Is a sprinkler installed in a parking garage, and won't the pipe freeze?
Yes, it is installed — but not wet; a dry pipe system is used. In a dry pipe system, there is pressurized air in the pipe; when the head opens, the air is released and water comes. This is mandatory in unheated parking garages, cold storage, and open storage areas.
How many sprinkler heads are needed?
This is the wrong question. Design is not determined by head count, but by hydraulic calculation based on hazard class: required water intensity (mm/min), the assumed area that will operate simultaneously, pipe diameters, and pump capacity. Head count is the result of this calculation, not its input.
Is fire detection also required where sprinklers are present?
Yes. A sprinkler activates when the fire reaches a certain temperature — that is, after the fire has grown. A detection system alerts much earlier and enables occupant evacuation. Additionally, sprinklers are not suitable for kitchen oil, flammable liquids, and electronics; different suppression systems are used in those cases.
I changed the use of my storage facility; is my sprinkler system sufficient?
Probably not. Sprinkler calculation depends on fire load and storage height; a system designed when it was an office becomes inadequate when it becomes a storage facility, and a system designed for general storage becomes inadequate when it becomes plastic storage. The calculation must be repeated when use changes.