Short answer: TS EN 12845+A2:2026 Clause 11.6 (EN p.69): water spray extensions may be connected to a sprinkler installation provided that the connection is not greater than 80 mm and that the additional water demand is taken into account when designing the water supplies (see Clause 8).

The only arrangement that is connected to a sprinkler installation yet does not work on sprinkler logic is the subsidiary water spray extension. Here all the nozzles are open; the only element that triggers the system is its own activation valve. TS EN 12845+A2:2026 devotes three paragraphs to this arrangement in Clause 11.6 and gives no design density. This article is limited to what the standard actually says and does not fill the density gap. Source: TS EN 12845+A2:2026, Clause 11.6, EN p.69 (TSE p.72).

1. The full content of Clause 11.6

Clause 11.6 (EN p.69) is three sentences:

These extensions use open sprinklers or sprayers connected to a sprinkler installation through their own activation valves (a deluge valve or a multiple control). Water spray extensions may be connected to a sprinkler installation provided that the connection is not greater than 80 mm and that the additional water demand is taken into account when designing the water supplies (see Clause 8). These installations are installed where intense and very rapidly spreading fires are expected and where it is desirable to apply water over the whole of an area in which a fire could start and spread.

Four binding elements follow from this:

Element Provision
Nozzle type Open sprinkler or sprayer (no thermal element)
Activation Its own valve: a deluge valve or a multiple control
Connection size ≤ 80 mm
Water demand The additional demand is included in the design of the water supply under Clause 8

2. What is a sprayer?

Clause 3.53 (EN p.20) defines the sprayer as follows:

sprayer: water spray nozzle giving a downward conical pattern of discharge

There are two related definitions:

The difference is clear: a sprinkler has a heat sensitive sealing device and each head opens on its own; a sprayer and an open sprinkler have no such device and all of them discharge together the moment the activation valve opens.

3. The scope limit: the standard gives no density

Clause 1 Scope (EN p.14) reads:

The requirements and recommendations of this European Standard also apply to any addition, extension, repair or other modification to a sprinkler system. They do not apply to water spray or deluge systems.

The same clause also states that the requirements of the standard may be used as a guide for other fixed firefighting systems, but that requirements specific to other extinguishing supplies need to be taken into account.

For the designer this means: the design density and the nozzle layout of the water spray extension itself are not in TS EN 12845+A2. Clause 11.6 regulates only the interface, that is the connection size, the activation valve and the effect of the water demand on the sprinkler supply. The density has to be based on another source (for example the requirements of the manufacturer of the protected equipment or another relevant standard), and that source must be stated explicitly in the project.

There is a similar limit for HHP4. The NOTE to Clause 6.2.4.1 (EN p.32): "HHP4 hazards are usually protected by deluge systems, which are outside the scope of this standard." In Table 3 (EN p.36) the HHP4 row reads "deluge (see NOTE)" instead of a density.

4. How the additional water demand reaches the sprinkler supply

Clause 11.6 requires the additional water demand to be taken into account under Clause 8. The relevant provisions of Clause 8 are:

The design flow on the sprinkler side is derived from the hazard class. Example: OH2, wet system. Table 3 (Clause 7.1, EN p.36) gives a design density of 5.0 mm/min and an area of operation of 144 m²; the product of these two is 5.0 x 144 = 720 l/min. For a pre-calculated system, Table 6 (Clause 7.3.1, EN p.39) gives, for OH2 wet and pre-action, 725 l/min and 1.4 + ps bar at the control valve set, and a maximum demand flow of 1 000 l/min at 1.0 + ps bar. The flow of the water spray extension is added on top of these values when the water supply is sized; the magnitude of the flow to be added is, however, a matter for the design source of the extension, not for Clause 11.6.

The standard contains no provision adding a hose reel or fire brigade allowance to the sprinkler design flow. The taking of water for other services is regulated separately in Clause 8.3 and Table 8, and the values given there are connection sizes, not a flow allowance.

5. Relationship with a combined supply

Since the water spray extension is part of the sprinkler installation, it is fed from the same supply. Where a separate hydrant or hose system is fed from the same supply alongside the sprinkler system, however, Clause 9.6.4 (EN p.56-57) applies. Combined supplies shall be superior single or duplicate supplies and shall satisfy four conditions:

In addition, Clause 9.5.1 (EN p.54) states that a pressure tank shall be "reserved for the sprinkler system and/or the water spray system", one of the few direct references to water spray in the standard.

6. The other place water spray appears in the standard: Annex F.7

Annex F is entitled "Additional measures to improve system reliability and availability" and applies, according to F.1, where national legislation requires it. F.7 is "Additional measures for theatres" (EN p.143):

In theatres with a separated stage (that is, where there is a safety curtain between the stage and the auditorium) the safety curtain shall be provided with a drencher line controlled by a quick opening valve (for example a plug valve) fitted in an accessible position. The water supply for the drenchers shall be taken from upstream of any control valve set. The stage shall be protected by a water spray installation with automatic and manual activation. Alternatively, stages not exceeding 12 m in overall height may be protected by sprinklers. All workshops, dressing rooms, scenery and store rooms and the spaces below the stage shall be protected by sprinklers.

The detail worth noting here is that the drencher supply is taken from upstream of the control valve set, whereas the subsidiary extension of Clause 11.6 is connected to the installation itself, that is downstream of the control valve set.

7. Implementation checklist (the standard's own provisions)

# Check Source
1 The connection size does not exceed 80 mm Clause 11.6, EN p.69
2 The extension has its own activation valve (deluge valve or multiple control) Clause 11.6, EN p.69
3 The additional water demand has been taken into account in the design of the water supply Clause 11.6 + Clause 8, EN p.69 and p.42
4 Where the supply feeds more than one system, conditions 9.6.4 a-d are satisfied Clause 9.6.4, EN p.56-57
5 The 12 bar pressure limit has not been exceeded Clause 8.2.1, EN p.42-43
6 The source for the design density of the extension itself is stated in the project (EN 12845 does not give one) Clause 1 Scope, EN p.14
7 The sprayers are also checked in the quarterly routine (cleaning of deposits, replacement of painted or distorted units) Clause 20.3.2.3, EN p.120

The seventh row is easily missed: Clause 20.3.2.3 is entitled "Sprinklers, multiple controls and sprayers" and applies the quarterly routine to all of them.

Frequently Asked Questions

What is the connection size limit for a water spray subsidiary extension?

TS EN 12845+A2:2026 Clause 11.6 (EN p.69): water spray extensions may be connected to a sprinkler installation provided that the connection is not greater than 80 mm and that the additional water demand is taken into account when designing the water supplies (see Clause 8).

How is a water spray extension activated?

Clause 11.6 (EN p.69): these extensions use open sprinklers or sprayers connected to a sprinkler installation through their own activation valves (a deluge valve or a multiple control). A sprayer is, according to Clause 3.53 (EN p.20), a water spray nozzle giving a downward conical pattern of discharge.

Does EN 12845 give a design density for water spray?

No. Clause 1 Scope (EN p.14) states expressly that the requirements and recommendations of this standard 'do not apply to water spray or deluge systems'. Clause 11.6 regulates only the connection size, the activation valve and the need to take the additional water demand into account; it gives no density in mm/min.

How does the additional water demand enter the hydraulic calculation?

Clause 11.6 (EN p.69) requires that 'the additional water demand is taken into account when designing the water supplies' and refers to Clause 8. The flow of the extension is added to the design flow on the sprinkler side and the water supply is sized accordingly. How the design flow of the extension itself is calculated is outside the scope of this standard.

Does a water spray extension lengthen the duration of the water supply?

Clause 8.1.1 (EN p.42) gives the durations by hazard class: LH 30, OH 60, HHP 90 and HHS 90 minutes. Where the supply serves more than one fixed firefighting system, Clause 9.6.4 c) applies: the duration of the supply shall not be less than that required for the most demanding system.

Where else does water spray appear in the standard?

Annex F.7 (EN p.143): in theatres with a separated stage the safety curtain is provided with a drencher line controlled by a quick opening valve fitted in an accessible position; the water supply for the drenchers is taken from upstream of any control valve set. The stage is protected by a water spray installation with automatic and manual activation; alternatively, stages not exceeding 12 m in overall height may be protected by sprinklers.

References

SprinkCalc — Fire Sprinkler Design Across Three Standards

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MEP Calc — 86+ Engineering Calculators

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Standards & References

TS 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.

FS

Fatih Selvi

Mechanical engineer and software developer with field experience in MEP and fire protection, working actively with NFPA, FM Global and BS EN 12845 on site projects.