How long do fire sprinkler heads last?

A fire sprinkler head has no fixed lifespan under the UK rules. There is no age at which the heads in a building must all be changed. A head stays in service for as long as it passes inspection, and in a clean, dry, heated building that is commonly several decades. What ends a head’s life is its condition, not its birthday. Sentry Sprinkler Protection inspects heads on every service visit, and this answer sets out when one has to come out and what the rules ask for as a system ages.

Why there is no expiry date

A sprinkler head is a simple, sealed part: a frame, a plug, a seal and a glass bulb or fusible link. Nothing in it wears from use, because in a normal life it is never used. What harms it is its surroundings: corrosion from damp or chemical air, dust and grease that coat it, paint from a redecoration, and knocks from people and machinery.

So BS EN 12845, the British and European standard for commercial sprinkler systems, and the LPC Rules that insurers apply on top of it, do not set a replacement age. They set an inspection regime and say what must be replaced when it is found.

When a head must be replaced

Finding	What the rules say
Painted head	Replaced, not cleaned. Paint slows the bulb or link (BS EN 12845, 20.3.2.3)
Distorted or damaged head	Replaced (20.3.2.3)
Head covered in dust or deposits	Carefully cleaned; replaced if it cannot be (20.3.2.3)
Head that has operated	Replaced with one of the correct type and temperature rating (LPC Rules, TB203)
Unopened heads near a fire	Checked for heat damage and replaced as necessary (TB203)
Weeping or leaking head	Replaced, never tightened

Those checks are part of the quarterly routine, so a properly serviced system should never carry a painted or damaged head for long. The servicing intervals guide sets out what happens at each visit, and the sprinkler repairs guide explains why a dripping head is changed rather than tightened.

The 25 year inspection

Age does matter once, at 25 years. BS EN 12845 recommends an inspection of the pipes and the heads at that point (Annex K), and the LPC Rules replace that annex with their own requirement for insured systems (TB203.3.8).

The work involves:

• Flushing the pipework from its remote ends until the water runs clear, and looking inside for debris and for the nodules that bacterial corrosion leaves (TB203.3.8.1).
• Removing sample heads from near the ends of range pipes, where debris settles, and inspecting the head and the pipe it came from.
• Testing the samples. Annex K suggests 20 heads of each type for an installation of up to 5,000 heads, rising to 100 for 40,000, checked for operation, operating temperature, K-factor, lodgement and thermal sensitivity (Table K.1).

If debris of 5 mm or more turns up, or there are blocked heads or persistent pinhole leaks, the debris has to be cleared from every installation that could be affected and the system’s performance proved again (TB203.3.8.1). Heads that come through the inspection in good condition stay in service. On systems with several installations, the LPC Rules then require each one to be re-inspected and flushed at least every ten years.

Dry pendent heads are the exception

One kind of head is sampled much sooner. Dry pendent heads, the ones on a dry drop pipe that protect cold stores and other spaces where water in the pipe would freeze, have representative samples removed and tested at the interval the manufacturer gives, or every five years where it gives none. The sample is 5 % of each batch or twenty heads, whichever is greater (LPC Rules, TB203 five-yearly routine).

The American 50 year rule

You may read that sprinkler heads must be replaced at 50 years. That comes from the American standard NFPA 25, which calls for 50-year-old heads to be replaced or sample tested. It does not apply to UK systems designed to BS EN 12845, which use the inspection and sampling regime above instead.

What you should have on site

BS EN 12845 requires a stock of spare heads, kept with the correct sprinkler spanner in a cabinet in a prominent place where the temperature stays at or below 27 °C (clause 20.1.4):

• at least 6 for a light hazard installation;
• at least 24 for ordinary hazard;
• at least 36 for high hazard;
• plus spares of any special heads in the building, such as high temperature, sidewall or concealed patterns.

The stock is replaced as soon as any are used. An empty spares cabinet is one of the first things an insurer’s surveyor notices.

Getting the heads checked

If you do not know when your heads were last inspected, or your system is approaching 25 years with nobody having mentioned it, a sprinkler service will tell you where it stands. If a head has been damaged or has operated, our emergency call-out line covers making the system safe and replacing it like for like.