Short answer: Clause 8.2.1 (TS p.45 / EN p.42): except during testing, the water pressure shall not exceed 12 bar at the equipment connections or locations defined in Clauses 8.2.1.1 and 8.2.1.2. On pumped systems, the increases in drive speed and pressure under the closed valve condition shall also be taken into account.

Pressure in a sprinkler system causes trouble not only when it is too low but also when it is too high: a sprinkler, a wet alarm valve or a mechanical pipe coupling operating above 12 bar falls outside the equipment window the standard accepts. TS EN 12845+A2:2026 sets that ceiling in Clause 8.2, and regulates the permission to take water from the system for other services in Clause 8.3 and Table 8. Source: TS EN 12845+A2:2026, Clause 8.1, Clause 8.2, Clause 8.3 and Table 8.

The 12 bar ceiling: Clause 8.2.1

Clause 8.2.1 (TS p.45 / EN p.42) is defined in a single sentence: except during testing, the water pressure shall not exceed 12 bar at the equipment connections or locations defined in Clauses 8.2.1.1 and 8.2.1.2. The pressure on pumped systems shall take into account the increases in drive speed and pressure that may arise from the closed valve condition.

The phrase "8.2.1.1 and 8.2.1.2" is critical: 8.2.1.2 brings those items within the limit, it does not exempt them.

Clause 8.2.1.1 - all types of sprinkler system:

Clause 8.2.1.2 - systems where the height difference between the highest and lowest sprinkler head does not exceed 45 m (TS p.46 / EN p.43):

The single exception: high rise buildings, Clause 8.2.2

Clause 8.2.2 (TS p.46 / EN p.43): on high rise sprinkler systems where the height difference between the highest and lowest sprinkler exceeds 45 m, and provided that all equipment subjected to pressures higher than 12 bar is fit for purpose, the water pressures may exceed 12 bar at these two locations only:

Sprinklers, alarm valves, stop valves and mechanical couplings are not on that list; they have to be kept below 12 bar in a high rise building too.

Clause 3.32 (TS p.21 / EN p.18) defines a high rise system: a sprinkler system in which the highest sprinkler is more than 45 m above the lowest sprinkler or the sprinkler pumps, whichever is the lower.

Where is zoning specified?

The pressure exemption and zoning are separate provisions. Clause 8.2.2 grants only the exemption; the requirement to divide the system is elsewhere:

Other 12 bar provisions: Clause 9.5.4.1 (TS p.57 / EN p.54) requires the pressure in a pressure tank not to exceed 12 bar; Annex K (TS p.162 / EN p.159) requires the pipework to be tested hydrostatically at the maximum static pressure or 12 bar, whichever is the greater, at the 25 year inspection.

Supplying other services: Clause 8.3

Clause 8.3 (TS p.46 / EN p.43): water for other services may be taken from the sprinkler system only where all of the following conditions are satisfied:

The last paragraph of the clause stands apart and is often overlooked: the sprinkler system pumps shall be separate from any hydrant system pumps unless a combined water supply complying with Clause 9.6.4 is used.

Table 8: the permitted connections

Table 8 (TS p.47 / EN p.44), "water connections for other services on low rise systems":

Type of water supply Acceptable number, size and purpose of connection
Town main; main and feed pipe ≥ 100 mm One connection of not more than 25 mm diameter, for non-industrial use
Town main; main and feed ≥ 150 mm One connection of not more than 40 mm diameter for non-industrial use; or one connection of not more than 50 mm diameter for fire hose reels (a further connection of not more than 40 mm for non-industrial use may be made near the first, fitted with a stop valve close to the feed end)
Elevated private reservoir, gravity tank or automatic pump One connection of not more than 50 mm diameter, for fire hose reels

NOTE: an additional supply arrangement with a check valve may be provided for the fire service.

On the marking side, Clause 18.2.4 (TS p.119 / EN p.116): stop valves controlling water supplies to other services from sprinkler system feed pipes or trunk mains are fitted with a plate and marked appropriately in raised letters, for example "Fire hose reels" or "Domestic water".

The water itself: Clause 8.1

Clause 8.1.1, duration (TS p.45 / EN p.42): LH 30 min, OH 60 min, HHP 90 min, HHS 90 min. NOTE: for town mains, inexhaustible sources and all pre-calculated systems, the duration is implicit in the requirements of the standard.

Clause 8.1.2, continuity: the water supply shall not be liable to be affected by frost, drought, flooding or other conditions which could reduce the flow, reduce the effective capacity or render the supply inoperative. The water shall not contain fibrous or other matter in suspension which could accumulate in the system pipework. Salt or brackish water shall not be retained in sprinkler installation pipework. Where no suitable fresh water source is available, a salt or brackish water supply may be used provided that the installation is normally filled with fresh water. (The text of the standard names no substance such as "calcium chloride"; the provision is about salt and brackish water.)

Clause 8.1.3, frost protection: the feed pipe and the control valve set shall be maintained at a minimum temperature of 4 °C.

Clause 10.4, water supply temperature (TS p.61 / EN p.58): the water supply temperature shall not exceed 40 °C. Where submersible pump sets are used, the water temperature shall not exceed 25 °C unless the motor is proven suitable up to 40 °C.

Backflow prevention, Clause 11.1.2.2 (TS p.69 / EN p.66): systems relying on antifreeze solution shall be fitted with backflow prevention devices to prevent contamination of the water. The same clause limits the number of sprinklers on an antifreeze protected section of pipework to 20 and, where more than two antifreeze sections are connected to one control valve set, the total to 100, and requires the specific gravity of the prepared solution to be checked with a suitable hydrometer.

The town main side

Pressure rules on the test and calculation side

Field note: the 12 bar ceiling comes under the most strain in basement valve rooms, where the closed valve pressure of the pump is superimposed on the static head of the building; the sentence in Clause 8.2.1 requiring the closed valve increase to be taken into account was written for exactly that case.

Frequently Asked Questions

What is the upper water pressure limit in EN 12845?

Clause 8.2.1 (TS p.45 / EN p.42): except during testing, the water pressure shall not exceed 12 bar at the equipment connections or locations defined in Clauses 8.2.1.1 and 8.2.1.2. On pumped systems, the increases in drive speed and pressure under the closed valve condition shall also be taken into account.

To which equipment does the 12 bar limit apply?

Clause 8.2.1.1, for all types of sprinkler system: 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 8.2.1.2 adds, for systems where the height difference between the highest and lowest sprinkler does not exceed 45 m, the pump outlets, wet alarm valves, stop valves and mechanical pipe couplings.

In which case may 12 bar be exceeded?

Clause 8.2.2 (TS p.46 / EN p.43): on high rise sprinkler systems where the height difference between the highest and lowest sprinkler exceeds 45 m, and provided that all equipment subjected to pressures above 12 bar is fit for purpose, the pressure may exceed 12 bar in two places only: at the pump outlets and in the risers and distribution pipes.

May water be taken from the sprinkler system for other services?

Clause 8.3 (TS p.46 / EN p.43) permits it if all four conditions are met: the connections shall be as specified in Table 8; the connection shall be made upstream of the control valve set through a stop valve fitted as close as practicable to the point of connection to the sprinkler feed pipe; the system shall not be a high rise system; and the system shall not protect a multi-storey building. In addition, the sprinkler system pumps shall be separate from any hydrant system pumps unless a combined supply complying with Clause 9.6.4 is used.

What diameter may a service connection have?

Table 8 (TS p.47 / EN p.44): where the town main and the feed pipe are 100 mm and above, one connection of not more than 25 mm for non-industrial use; where they are 150 mm and above, one connection of not more than 40 mm for non-industrial use, or one connection of not more than 50 mm for fire hose reels (a further connection of not more than 40 mm may be made near that point, with a stop valve close to the feed end). For an elevated private reservoir, a gravity tank or an automatic pump, one connection of not more than 50 mm for fire hose reels only.

May salt water be used in sprinkler pipework?

Clause 8.1.2 (TS p.45 / EN p.42): salt or brackish water shall not be retained in sprinkler installation pipework. Where no suitable fresh water source is available, a salt or brackish water supply may be used provided that the installation is normally filled with fresh water.

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.