Sprinkler Heads and Sprinkler Types: A Practical Guide

The head is the working end of every fire sprinkler installation. It is a small, precisely made valve that stays closed for decades and then opens, without any outside signal, when the air around it becomes hot enough. Choosing the right head for each space is one of the quieter decisions in building services design, but it determines how quickly water arrives and where it lands.

This guide explains how a head is built, the main orientations and styles, what the coloured glass bulbs mean, the difference between standard and fast response, and the practical points that matter when ceilings and layouts change. For the system as a whole, read our companion piece on the fire sprinkler system.

Anatomy of a sprinkler head

A typical head has five parts. The frame is threaded into the pipe fitting and carries everything else. The orifice is the opening through which water discharges, and its size sets the flow at a given pressure. A cap or seal sits over the orifice. The thermal element, either a glass bulb or a fusible link, holds the cap in place against water pressure. The deflector, a toothed plate at the end of the frame, breaks the stream into a spray of the intended shape.

When the thermal element reaches its rated temperature it fails by design. A glass bulb contains a liquid that expands as it heats until the bulb shatters. A fusible link is two metal plates joined by a solder alloy that melts at a set temperature. Either way the cap is released and water flows. Once a head has operated it cannot be reset; it is replaced with an identical head of the same type, rating and response.

Orientation: pendent, upright and sidewall

Heads are made to work in a particular position, and the deflector is shaped accordingly. Installing a head the wrong way up gives a poor spray pattern.

Pendent heads hang down from pipework above a ceiling, with the deflector spreading water in a downward umbrella. They are the most common type in finished interiors.
Upright heads point upward from pipes run below the soffit, with the deflector throwing water up and then down. They suit exposed spaces such as plant rooms, car parks and warehouses where there is no ceiling, and they are less exposed to knocks from below.
Sidewall heads are mounted on a wall near the ceiling and throw water across the room. They are useful in corridors, hotel rooms and spaces where running pipes across the ceiling is impractical.

Each orientation has its own spacing and clearance rules, set by the design code and the head’s listing, including distance below the ceiling or soffit and distance from walls and obstructions.

Recessed and concealed styles

In finished interiors, appearance matters. A recessed pendent sits partly within an escutcheon in the ceiling so less of the body is visible. A concealed head sits above a flat cover plate flush with the ceiling. The cover plate is held on by a low-melting solder, so in a fire it drops away first, the head then lowers into position and operates in the normal way.

Concealed heads are neat, but they carry obligations. Cover plates must not be painted, glued or sealed, because that can stop them releasing, and they must be the matching plate for that head with the correct release temperature. Decorators and ceiling contractors should be told plainly that cover plates are part of the fire protection, not trim.

Glass bulb colours and temperature ratings

The colour of the liquid in a glass bulb indicates its nominal operating temperature, using a widely adopted international colour code. Common examples are:

Orange — about 57°C
Red — about 68°C, the most common rating for ordinary interiors
Yellow — about 79°C
Green — about 93°C
Blue — about 141°C
Purple — about 182°C

Higher ratings exist for very hot environments. The rule is to choose a rating comfortably above the highest ambient temperature the head will see in normal service, so it does not operate unintentionally, while keeping it as low as practical so it responds promptly in a fire. Heads near skylights, ovens, unventilated roof spaces or hot plant are typical places where a higher rating is chosen. Fusible-link heads use frame or link colour codes for the same purpose, and the exact rating should always be confirmed from the head’s marking rather than assumed from colour alone.

Response speed, coverage and special heads

Two heads with the same temperature rating can respond at different speeds, because the thermal element’s mass and design affect how quickly it heats up. This is expressed through a response time index. Standard response heads have a heavier element and are used where the aim is fire control over a larger area. Quick response heads have a thinner bulb or lighter link and operate sooner, which improves life safety in occupied spaces and is commonly used in light hazard areas.

Beyond the everyday heads there are several specialised types:

Extended coverage heads protect a larger floor area per head under specific conditions of their listing.
Residential heads are designed to keep conditions survivable in a room of fire origin, with a spray pattern that wets walls high up.
Early suppression fast response heads, often called ESFR, deliver large drops at high flow to suppress fires in high-piled storage, and are used in warehouses.
Open heads, with no thermal element at all, are used in deluge systems where water is released through every head at once.
Dry pendent heads include an extension that keeps water out of the drop in cold areas.

A related term is the K-factor, a number describing how much water the head discharges for a given pressure. Larger K-factors pass more water and are used for higher hazards.

Choosing and maintaining heads in Singapore

In Singapore the SCDF Fire Code sets when sprinklers are required, and its clause on sprinkler installation refers to SS CP 52, the local code of practice for automatic fire sprinkler systems, for installation and testing. Head selection, spacing and response type follow that code and the head’s listing. The Fire Code also recognises early suppression fast response sprinklers and other systems where they meet the intent of the code.

The practical risks to heads are almost always caused by later works. False ceilings installed below existing heads, new partitions that create unprotected rooms, cabinetry or signage too close to deflectors, painted bulbs and cover plates, and storage stacked up to the ceiling all compromise performance. Any head that is damaged, corroded, painted or has been knocked should be replaced like for like by a competent sprinkler contractor. When a renovation changes ceiling levels or room layouts, the head layout needs to be reviewed as part of the works, and where it forms part of an approved fire safety plan, the change goes through a Qualified Person. Sprinklers sit alongside passive measures such as fire-rated doors and compartment walls, and both need to survive the fit-out intact.

Frequently asked questions

What does the colour of a sprinkler bulb mean?

The liquid colour in a glass bulb indicates the nominal temperature at which it shatters. Red, at about 68°C, is the most common for ordinary rooms, orange is slightly lower, and yellow, green, blue and purple indicate progressively higher ratings for hotter environments. Always confirm the rating from the head’s marking.

Can I paint over a sprinkler head or cover plate?

No. Paint can insulate the thermal element, delay operation or glue a concealed cover plate in place so it never drops. A painted head should be replaced, not cleaned, by a competent sprinkler contractor using an identical head of the same type, rating and response.

What is the difference between pendent and upright heads?

A pendent head hangs down from pipework above a ceiling and sprays water downward. An upright head points up from pipework below the soffit and throws water up against the deflector and then down. Each has its own deflector design, and fitting one in the other’s position gives a poor spray pattern.

Are quick response heads better than standard response heads?

They are suited to different purposes. Quick response heads operate sooner and are favoured in occupied, light hazard spaces for life safety. Standard response heads are used where the design aims to control a fire over a larger area. The code and the hazard classification determine which is required.

Does a sprinkler head need replacing after it activates?

Yes. A head that has operated cannot be reset, because its thermal element has broken by design. It must be replaced with an identical head, and the system restored, tested and returned to service by a competent contractor as soon as possible.

Changing ceilings, partitions or room use and need the fire and structural implications reviewed? Talk to our consultancy or get in touch.