Source: TS EN 12845+A2:2026, Annex K (informative) "Twenty-five year inspection" and Table K.1, EN p.159.
Annex K is one of the shortest annexes in the standard: it has no sub-clause numbers and consists of plain text and a single table. There are no clauses such as K.1, K.2, K.3 or K.4 in this annex. The annex is informative; the provisions are in the "should" form.
Scope of the annex
The opening of Annex K (EN p.159): "After 25 years the pipes and the sprinklers should be inspected."
So the annex defines two separate inspection subjects: the pipework and the sprinklers. They are dealt with together.
Inspection of the pipework
| Subject | Provision |
|---|---|
| Flushing | The pipework should be thoroughly flushed out |
| Hydrostatic test | It should be tested to a pressure equal to the maximum static pressure or 12 bar, whichever is the higher |
| Inspection | The pipework should be inspected internally and externally |
| Range pipe sampling | At least one metre length of range pipe should be inspected per 100 sprinklers |
| Sampling by diameter | Two pipe sections of at least one metre length of each pipe diameter should be inspected |
| Defects | All defects which might adversely affect the performance of the system should be eliminated |
Source: Annex K, EN p.159.
How many installations are inspected?
| System type | Scope |
|---|---|
| Wet pipe systems | At least one sprinkler installation per building should be checked |
| Where several wet control valve sets are installed in one building | Only 10% need be inspected |
| Dry pipe systems | Such a reduction is not allowed in the number of installations to be checked |
Source: Annex K, EN p.159.
Table K.1: Number of sprinklers of each available type to be tested
| Total number of sprinklers installed | Number of sprinklers to be inspected |
|---|---|
| ≤ 5 000 | 20 |
| ≤ 10 000 | 40 |
| ≤ 20 000 | 60 |
| ≤ 30 000 | 80 |
| ≤ 40 000 | 100 |
Source: Table K.1, EN p.159.
The title of the table matters: the number applies separately to each available type. Annex K does not say that separate grouping by temperature rating is required; the distinction is by type.
The text of Annex K (EN p.159): "A number of sprinklers should be removed and tested to ensure that they are fully functional. Table K.1 specifies the scope of sampling as a function of the total number of sprinklers installed."
Properties to be evaluated on the sprinklers
Annex K (EN p.159) lists six items:
- a) operation;
- b) operation temperature;
- c) variation of K-factor;
- d) spray obstacles;
- e) lodgement;
- f) thermal sensitivity.
The standard gives no numerical acceptance criterion for these items (for example a percentage deviation limit for the K-factor or an RTI limit for thermal sensitivity).
Where Annex K sits in the maintenance programme of the standard
Annex K is not part of the periodic service programme in Clause 20.3 (EN p.120 onwards); it is a 25 year milestone separate from it. The programme steps of Clause 20.3 are as follows:
| Interval | Subject | Source |
|---|---|---|
| 13 weeks maximum | Quarterly routine (review of the hazard, sprinklers, pipes and hangers, water supplies and their alarms, electrical supplies, stop valves, flow alarms, spare parts) | Clause 20.3.2, EN p.120-121 |
| 6 months maximum | Half-yearly routine (dry alarm valves, electrical wiring of the fire service and remote centre alarms) | Clause 20.3.3, EN p.121 |
| 12 months maximum | Annual routine (full load flow test of the pump set, diesel failure-to-start test, tank ball valves, suction chambers and strainers) | Clause 20.3.4, EN p.121-122 |
| 3 years maximum | Three-yearly routine (internal examination of storage and pressure tanks; water supply stop, alarm and non-return valves) | Clause 20.3.5, EN p.122 |
| 10 years maximum | Ten-yearly routine (cleaning and internal examination of all storage tanks) | Clause 20.3.6, EN p.122 |
| 25 years | Inspection of pipes and sprinklers | Annex K, EN p.159 |
In addition, Clause 21 (EN p.123): the sprinkler system is inspected periodically by a qualified person at least once a year (see Annex Q). The inspection report assesses whether the system complies with this standard in terms of its adequacy for maintenance, operation and the risk, and a list of deviations is drawn up.
What the standard does not say in Annex K
- A figure such as a minimum of 4 sprinklers per group, or an additional sampling rule above a given number of sprinklers. The sampling is in Table K.1.
- Numerical acceptance criteria (percentage limits for the K-factor, thermal sensitivity or operation temperature).
- A re-sampling procedure such as taking a double sample or replacing all sprinklers if one sample fails.
- A schedule of first inspection age and repeat interval according to sprinkler type or environment. Annex K covers only 25 years.
- A water distribution pattern test, spring pressure measurement or corrosion deposit analysis. The evaluation items are limited to a) to f).
- A retention period for the test results.
Field note
Field note (this is engineering interpretation, not part of the standard): in the 25 year inspection the real information comes from the internal condition of the pipes rather than from the sprinkler samples; range pipe sampling and sampling by diameter show how much corrosion and deposit build-up have changed the hydraulics of the system. For this reason, when the inspection is planned, the locations from which the sections will be taken should be decided in advance with the most unfavourable points of the installation in mind.
Frequently Asked Questions
How many sprinklers are tested under Annex K?
TS EN 12845+A2:2026 Table K.1 (EN p.159) gives the number of sprinklers to be tested of each available type as a function of the total number of sprinklers installed: 20 for ≤ 5 000; 40 for ≤ 10 000; 60 for ≤ 20 000; 80 for ≤ 30 000; 100 for ≤ 40 000.
What is done to the pipework?
Annex K (EN p.159): the pipework should be thoroughly flushed out and hydrostatically tested to a pressure equal to the maximum static pressure or 12 bar, whichever is the higher. The pipework should be inspected internally and externally; at least one metre length of range pipe should be inspected per 100 sprinklers, and two pipe sections of at least one metre length of each pipe diameter should be inspected.
How many installations in a building are inspected?
Annex K (EN p.159): in the case of wet pipe systems, at least one sprinkler installation per building should be checked. If several wet control valve sets are installed in one building, only 10% need be inspected. In the case of dry pipe systems, such a reduction of the number of installations to be checked is not allowed.
What is evaluated on the sprinklers that are removed?
Annex K (EN p.159) lists six items: a) operation; b) operation temperature; c) variation of K-factor; d) spray obstacles; e) lodgement; f) thermal sensitivity.
Is Annex K normative?
No. Annex K is informative and its text is in the 'should' form (EN p.159). The annual periodic inspection is covered by normative Clause 21 (EN p.123), which refers to informative Annex Q.
References
- TS EN 12845+A2:2026 Annex K and Table K.1 (EN p.159)
- TS EN 12845+A2:2026 Clauses 20.3.2, 20.3.3 (EN p.120-121)
- TS EN 12845+A2:2026 Clauses 20.3.4, 20.3.5, 20.3.6 (EN p.121-122)
- TS EN 12845+A2:2026 Clause 21 (EN p.123)
- TS EN 12845+A2:2026 Annex Q (EN p.165)
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Download MEP Calc on the App StoreTS EN 12845+A2:2026 (EN 12845:2015+A2:2026) Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance; TS EN 12845-2:2025 (EN 12845-2:2024) ESFR and CMSA sprinkler systems. Every figure in this article is taken from the published standard text; clause, table and page references are listed under References. General information only, not a substitute for the standard or for a design review.