Annex E (normative, EN p.139-142) of TS EN 12845+A2:2026 (EN 12845:2015+A2:2026) specifies the particular requirements for sprinkler protection in high-rise buildings. The annex is a short and precise text: three main clauses (E.1, E.2, E.3) and two typical layout figures. The content of the annex and the body clauses linked to it are set out below in order.
1. The threshold: 45 m
Clause E.1 General (EN p.139): The requirements of this annex shall apply to the sprinkler protection of multi-storey buildings where the difference in height between the highest and the lowest sprinkler exceeds 45 m.
The same threshold also appears in the body. Clause 5.5 (EN p.30): where the difference in height between the highest and the lowest sprinklers in a system or building exceeds 45 m, the requirements of Annex E shall apply. In addition, the difference in height between the highest and the lowest sprinkler in an installation connected to a single control valve set shall not exceed 45 m.
The criterion is not the number of storeys or the height of the building but the vertical difference between the sprinklers.
2. The hazard class limit
Clause E.1 (EN p.139) continued: The requirements may be applied to buildings designed for occupancies where the hazard is not greater than OH3. High-rise systems with a hazard greater than OH3 require specific fire engineering solutions and expert advice should be sought.
Clause E.2.1 Hazard group (EN p.139): High-rise sprinkler systems shall comply with the requirements for Ordinary Hazard Group III (OH3) protection.
The design equivalent of OH3 is fixed by Table 3 (Clause 7.1, EN p.36): a density of 5.0 mm/min and an area of operation of 216 m² (wet or pre-action system). The water supply duration is 60 min for OH under Clause 8.1.1 (EN p.42).
3. Design criteria (Clause E.2)
E.2.2 Division of high-rise sprinkler systems
High-rise sprinkler systems shall be divided into sprinkler installations such that the difference in height between the highest and the lowest sprinkler in any installation does not exceed 45 m (see Figures E.1 and E.2).
E.2.3 Standing water pressures at non-return and alarm valves
- The minimum standing pressure at the inlet of any non-return or alarm valve shall not be less than 1.25 times the difference in static head between the valve and the highest sprinkler in the installation.
- Non-return valves controlling the flow into an installation shall operate correctly without the ratio of the service pressure to the installation pressure exceeding 1.16:1, as measured by valve lift and pressure equalisation on the upstream side of the non-return valve.
E.2.4 Calculation of distribution pipes for pre-calculated systems
The main distribution pipes (including risers and drops) between the highest design point in the installation and the zone subsidiary stop valve at the same floor level shall be sized by hydraulic calculation. The maximum friction loss shall not exceed 0.5 bar at a flow rate of 1 000 l/min (see 13.3.4.2).
Where the sprinkler protection in an installation is at various floor levels, the pressure loss permitted between the design points at the lower levels and the zone subsidiary stop valves may be increased by the difference in static head gain between the sprinklers at the level concerned and the highest sprinkler in the installation.
E.2.5 Water pressures
Pipes, fittings, valves and other equipment shall be capable of withstanding the maximum pressure likely to be encountered. To overcome the problem of pressures exceeding 12 bar, hydraulic alarm gongs may be driven through a pressure reducing valve or from a secondary water supply such as a town main controlled by a diaphragm valve connected to the alarm port of the main installation control valve set.
4. The 12 bar rule and its high-rise exception
Clause 8.2.1 (EN p.42): Other than during testing, the water pressure shall not exceed 12 bar at the following equipment connections or locations (8.2.1.1, for all types of sprinkler system): a) sprinklers; b) multiple jet controls; c) water flow detectors; d) dry pipe and pre-action alarm valves; e) accelerators and exhausters; f) water motor alarms; g) zone control valves. The pressure in pumped systems shall take into account the increase in drive speed and pressure due to the closed valve condition.
8.2.1.2: in systems where the difference in height between the highest and the lowest sprinkler heads does not exceed 45 m, the same 12 bar limit also applies at: a) pump outlets; b) wet alarm valves; c) stop valves; d) mechanical pipe couplings.
Clause 8.2.2 (EN p.43): in high-rise sprinkler systems where the difference in height between the highest and the lowest sprinkler exceeds 45 m, and provided that all equipment subjected to a pressure higher than 12 bar is suitable for that purpose, the water pressures may exceed 12 bar at the following locations: a) pump outlets; b) risers and distribution pipes.
There is a related prohibition as well: when Clause 8.3 (EN p.43) lists the conditions for taking water from a sprinkler system for other services, item c) states that "the sprinkler system shall not be a high-rise system" and item d) that "the sprinkler system shall not protect a multi-storey building".
5. Water supplies (Clause E.3, EN p.140)
E.3.1 Types of water supply
The system shall have at least one superior single water supply.
E.3.2 Pressure and flow requirements for pre-calculated installations
The water supply shall be designed to meet the minimum pressure and flow condition specified in Table 6 at the outlet of the zone subsidiary stop valve; ps is taken as the pressure difference equivalent to the height of the highest sprinkler above the installation zone subsidiary stop valve.
The values in Table 6 (Clause 7.3.1, EN p.39) for an OH3 wet system: 1 100 l/min @ 1.7 + ps bar and a maximum demand of 1 350 l/min @ 1.4 + ps bar.
E.3.3 Water supply characteristics for pre-calculated installations
The water supply characteristics shall be determined by hydraulic calculation of the pipework upstream of the outlet of the zone subsidiary stop valve, at the high and low flow rates specified in Table 6, and shall include the calculations at the water supply datum point.
E.3.4 Pump set performance for pre-calculated installations
Automatic pump sets shall have characteristics in accordance with Table 16. NOTE: pressures are taken at the pump outlet or, in multi-stage pumps, at the relevant stage, on the discharge side of any orifice plate.
Table 16 (Clause 10.7, EN p.62) gives three height bands for OH3 wet or pre-action systems:
| OH3 wet or pre-action | Nominal data | Characteristic 1 | Characteristic 2 |
|---|---|---|---|
| h ≤ 15 m | 1.4 bar / 2 250 l/min | 2.9 bar / 1 350 l/min | 3.2 bar / 1 100 l/min |
| 15 < h ≤ 30 m | 2.0 bar / 2 700 l/min | 4.4 bar / 1 350 l/min | 4.7 bar / 1 100 l/min |
| 30 < h ≤ 45 m | 2.5 bar / 3 100 l/min | 5.9 bar / 1 350 l/min | 6.2 bar / 1 100 l/min |
NOTE 2 (same table): in buildings exceeding the heights shown, it shall be proved that the pump characteristics are adequate to provide the flow rates and pressures specified in 7.3.1.
6. Figures E.1 and E.2: two typical layouts
Annex E shows two typical layouts (EN p.141-142): Figure E.1 a high-rise system fed by a pump set, Figure E.2 with gravity tanks and feed pumps. The key to both figures is the same and lists the mandatory components of the system: 1 storage tank, 2 multi-stage pump, 3 flow meter, 4 water supply datum point, 5 alarm valve station (with bypass arrangement), 6 flow test and zone drain, 7 zone subsidiary stop valve, 8 water flow alarm switch, 9 sprinkler head, 10 water flow alarm switch test valve and zone drain valve.
7. Other clauses linked to Annex E
- Pump room (Clause 10.3.1, EN p.57): pump sets shall be housed in a compartment with a fire resistance of at least 60 min, used for no purpose other than fire protection. In order of preference: a separate building; a building adjoining a sprinkler protected building with direct access from outside; a compartment within a sprinkler protected building with direct access from outside.
- Pump room temperature (Clause 10.3.3, EN p.58): at least 4 °C for electric pump sets, at least 10 °C for diesel pump sets.
- Multiple pump arrangement (Clause 10.2, EN p.57): where two pumps are installed, each shall be capable of providing the specified flow rates and pressures independently; where three pumps are installed, each pump shall be capable of providing at least 50% of the specified flow rate at the specified pressure. Where more than one pump is installed on a superior or duplicate water supply, not more than one of them shall be driven by an electric motor.
- Zoning (Annex D, EN p.136-137): the zone subsidiary stop valve, water flow alarm switch and zone test/drain facilities referred to by Annex E are defined in Annex D. The NOTE to D.1 states that zoning is required in Annex E and Annex F.
- Fire resisting separation (Clause 5.3, EN p.30): the separation between a sprinkler protected area and an unprotected area shall have a fire resistance determined by the authority, but in no case less than 60 min.
Field note: The whole of Annex E rests on two ideas: limiting the static head seen by a single installation and guaranteeing that the valves also operate correctly under that head. In a high-rise building the critical item of the design is usually not the flow rate but the pressure rating of the valves and fittings.
Frequently Asked Questions
To which buildings does Annex E apply?
TS EN 12845+A2:2026 Clause E.1, EN p.139: the requirements of this annex shall apply to the sprinkler protection of multi-storey buildings where the difference in height between the highest and the lowest sprinkler exceeds 45 m. The requirements may be applied to buildings designed for occupancies where the hazard is not greater than OH3; high-rise systems with a hazard greater than OH3 require specific fire engineering solutions and expert advice should be sought. Clause 5.5, EN p.30 repeats the same 45 m threshold.
To which hazard class is a high-rise system designed?
Clause E.2.1, EN p.139: high-rise sprinkler systems shall comply with the requirements for Ordinary Hazard Group III (OH3) protection.
How is a high-rise system divided?
Clause E.2.2, EN p.139: high-rise sprinkler systems shall be divided into sprinkler installations such that the difference in height between the highest and the lowest sprinkler in any installation does not exceed 45 m (see Figures E.1 and E.2). Clause 5.5, EN p.30: the difference in height between the highest and the lowest sprinkler in an installation connected to a single control valve set shall not exceed 45 m.
What is the minimum standing pressure at the inlet of a non-return or alarm valve?
Clause E.2.3, EN p.139: the minimum standing pressure at the inlet of any non-return or alarm valve shall not be less than 1.25 times the difference in static head between the valve and the highest sprinkler in the installation. Non-return valves controlling the flow into an installation shall operate correctly without the ratio of the service pressure to the installation pressure exceeding 1.16:1.
Where may the 12 bar limit be exceeded in a high-rise building?
Clause 8.2.1, EN p.42: other than during testing, the water pressure shall not exceed 12 bar at sprinklers, multiple jet controls, water flow detectors, dry pipe and pre-action alarm valves, accelerators and exhausters, water motor alarms and zone control valves. Clause 8.2.2, EN p.43: in high-rise systems where the difference in height between the highest and the lowest sprinkler exceeds 45 m, the pressure may exceed 12 bar at the pump outlets and in the risers and distribution pipes, provided that all equipment subjected to a pressure higher than 12 bar is suitable for that purpose.
References
- TS EN 12845+A2:2026 (EN 12845:2015+A2:2026), Clauses 5.3 and 5.5 (EN p.30)
- TS EN 12845+A2:2026, Clause 7.1 and Table 3 (EN p.35-36)
- TS EN 12845+A2:2026, Clause 7.3.1 and Table 6 (EN p.39)
- TS EN 12845+A2:2026, Clauses 8.1.1 and 8.2.1, 8.2.1.1, 8.2.1.2 (EN p.42)
- TS EN 12845+A2:2026, Clauses 8.2.2 and 8.3 (EN p.43)
- TS EN 12845+A2:2026, Clauses 10.2 and 10.3.1 (EN p.57), Clause 10.3.3 (EN p.58)
- TS EN 12845+A2:2026, Clause 10.7 and Table 16 (EN p.62)
- TS EN 12845+A2:2026, Annex D, Clause D.1 (EN p.136)
- TS EN 12845+A2:2026, Annex E, Clauses E.1, E.2.1, E.2.2, E.2.3, E.2.4, E.2.5 (EN p.139)
- TS EN 12845+A2:2026, Clauses E.3.1, E.3.2, E.3.3, E.3.4 (EN p.140)
- TS EN 12845+A2:2026, Figure E.1 (EN p.141) and Figure E.2 (EN p.142)
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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.