Source: TS EN 12845+A2:2026, Clause 17 (EN p. 111-115) and Clause 19.1.1 (EN p. 117). All values below are from the standard's own text.
In EN 12845 the pipework is gathered into a single clause: Clause 17. That clause deals in turn with underground piping (17.1.1), above ground piping (17.1.2), welding (17.1.3), flexible joints (17.1.4), concealment (17.1.5), protection against damage (17.1.6), painting (17.1.7), drainage (17.1.8) and copper (17.1.9). Supports are in Clause 17.2, pipework in concealed spaces in Clause 17.3.
Clause 17.1.1: underground pipework
The standard is brief here. Pipes are laid in accordance with the recommendations of the supplier and have adequate resistance to corrosion. The NOTE to the clause recommends the following types:
- cast iron
- ductile iron
- spun cement
- reinforced glass fibre
- polyethylene high density
Adequate measures are also taken to prevent damage to the pipe, for example from the passage of vehicles. The standard gives no burial depth, bedding material or thrust block calculation for underground pipe; those subjects are not regulated in the text.
The terminology also has to be read from the standard's own definitions: Clause 3.78 (EN p. 22) defines the supply pipe as the pipe connecting a water supply to a trunk main or to an installation control valve set; Clause 3.82 defines the trunk main as the pipe connecting two or more supply pipes to the control valve sets.
Clause 17.1.2: above ground pipework
Pipework downstream of the control valves is of steel, copper (Clause 17.1.9) or another material conforming to the appropriate specifications valid where the system is used.
| Case | Minimum wall thickness requirement |
|---|---|
| Steel pipe of nominal size equal to or less than 150 mm; threaded, cut grooved or otherwise machined | ISO 65 |
| Steel pipe with an end formed without significantly reducing the wall thickness (such as roll grooving or weld end preparation) | ISO 4200 series D |
| Cases where mechanical pipe joints are used | Additionally in accordance with the manufacturer's recommendations |
Copper pipes conform to EN 1057. For dry, alternate or pre-action installations galvanized steel should be preferred.
The minimum pipe sizes are in Table 36 (Clause 13.4.5, EN p. 103): 20 mm for LH; 20 mm for horizontal and vertical pipes feeding a single sprinkler with a K-factor not exceeding 80 in OH and HH; 25 mm in all other cases. The provisions below that table matter: on the installation side of the control valve set, pipe sizes may only reduce in the direction of water flow (except in grid and loop arrangements); an upright sprinkler shall not be connected to a pipe of more than 65 mm diameter (50 mm where insulated); a pendent sprinkler shall not be connected directly to a pipe of more than 80 mm diameter, and for larger sizes an arm pipe is fitted so that the distance between the sprinkler deflector and the side of the main pipe is not less than 1.5 times the pipe diameter.
Clauses 17.1.3 and 17.1.4: welding and flexible joints
Welding (17.1.3): pipes and fittings of less than 50 mm diameter shall not be welded on site unless the installer uses an automatic welding machine. In no case shall welding in position, flame cutting, brazing or any other hot work be carried out. In welding, all joints are continuously welded, the inside of the weld does not obstruct the water flow and the pipe is free from burrs and slag. Welders are approved in accordance with EN ISO 9606-1.
Flexible joints (17.1.4): where relative movement is expected between pipe sections (because of an expansion joint or certain rack types, for example), a flexible section or joint is fitted at the point of connection to the distribution main. Before installation this element shall withstand a test pressure of four times the maximum working pressure or 40 bar, whichever is the greater, and shall contain no component that could impair the integrity or performance of the system in a fire. Flexible pipes contain an inner tube of stainless steel or non-ferrous metal that permanently retains pressure, shall not be installed in the fully stretched position and shall not be used to take up axial misalignment between the distribution main and the supply pipes of intermediate level sprinklers.
Clauses 17.1.5-17.1.8: access, protection, paint, drainage
- 17.1.5: pipes are installed so that they are readily accessible for repair and alteration and shall not be embedded in concrete floors or ceilings. As far as possible, pipework should not be run in concealed spaces that make inspection and repair difficult.
- 17.1.6: measures are taken against mechanical damage over walkways with low headroom, at intermediate levels or in similar locations. Where it is unavoidable for the supply pipe to pass through a building without sprinklers, it is installed at ground level and enclosed with suitable fire resistance and protection against mechanical damage.
- 17.1.7: ungalvanized ferrous pipework is painted where the environmental conditions require it. Galvanized pipework is painted wherever the coating has been damaged, for example as a result of threading.
- 17.1.8: it is ensured that all pipework can be drained; where a point cannot be drained through the drain valve at the control valve set, an additional valve is fitted in accordance with Clause 15.4. In dry, alternate and pre-action installations range pipes have a fall of at least 0.4 % towards the distribution pipe and distribution pipes a fall of at least 0.2 % towards the relevant drain valve. Range pipes are connected to distribution pipes only from the side or from the top.
Clause 17.2: supports and hangers
Supports are fixed directly to the building and, where necessary, to machinery, storage racks or other structures; they shall not be used to carry other installations; they are of the adjustable type; they fully encircle the pipe and shall not be welded to the pipe or the fittings. Pipes of more than 50 mm diameter shall not be supported from profiled steel sheet or aerated concrete decking. No part of a support may be of combustible material and nails shall not be used.
Spacing (17.2.2): no more than 4 m apart on steel pipe and 2 m apart on copper pipe. For diameters over 50 mm these distances may be increased by 50 % provided that either two independent supports are fitted directly to the structure or a support bearing a load 50 % greater than that called for in Table 40 is used. Where mechanical joints are used there is at least one support within 1 m of each joint and at least one support on each pipe section. The distance from a terminal sprinkler to a support shall not exceed 0.9 m at 25 mm diameter and 1.2 m at larger diameters; the distance from an upright sprinkler to a support shall not be less than 0.15 m. Vertical pipes longer than 2 m, and vertical pipes longer than 1 m feeding a single sprinkler, require an additional support.
Table 40 (EN p. 114):
| Nominal pipe diameter d (mm) | Minimum load bearing capacity at 20 °C (kg) | Minimum cross section (mm²) | Minimum length of anchor bolt (mm) |
|---|---|---|---|
| d ≤ 50 | 200 | 30 (M8) | 30 |
| 50 < d ≤ 100 | 350 | 50 (M10) | 40 |
| 100 < d ≤ 150 | 500 | 70 (M12) | 40 |
| 150 < d ≤ 200 | 850 | 125 (M16) | 50 |
Table 41 gives the minimum dimensions of flat iron rods and clips: for d ≤ 50 mm, galvanized flat iron rod 2.5 mm, ungalvanized 3.0 mm, galvanized clip 25 × 1.5 mm, ungalvanized 25 × 3.0 mm; for 50 < d ≤ 200 mm the rods are the same and the galvanized clip is 25 × 2.5 mm.
Clause 17.3: pipework in concealed spaces
In false ceilings above OH occupancies, the sprinklers above the ceiling may be fed from the same range pipes as the sprinklers below the ceiling; in pre-calculated systems the sprinklers are counted cumulatively when the pipe size is determined (17.3.2). In all other cases the sprinklers in the concealed space are fed from separate range pipes, and in pre-calculated systems the distribution pipe feeding sprinklers both inside and outside the concealed space shall not be less than 65 mm in diameter (17.3.3).
Commissioning tests: Clause 19.1.1
| Test | Clause | Requirement |
|---|---|---|
| Pneumatic test (dry pipework) | 19.1.1.1 | At least 2.5 bar for at least 24 hours; any pressure loss greater than 0.15 bar in 24 hours is corrected |
| Hydrostatic test (all pipework) | 19.1.1.2 | At least 2 hours; not less than 15 bar or 1.5 times the maximum pressure to which the system will be subjected, whichever is the greater, both measured at the installation control valves |
Clause 19.1.1.1 also states that where climatic conditions prevent the hydrostatic test being carried out immediately after the pneumatic test, it shall be done as soon as conditions permit. Clause 19.1.1.2 requires care to be taken that no system component is subjected to a pressure higher than that recommended by its supplier.
These are commissioning tests. Their counterpart in the maintenance schedule is separate: Clause 20.3 sets the service and maintenance programme, and Annex K (EN p. 159) deals with the 25 year inspection and recommends that the pipework be tested hydrostatically at the maximum static pressure or at 12 bar, whichever is the higher.
Flushing connections are in Clause 15.6 (EN p. 109): they are fitted to the end branches of the installation distribution pipes and are of the same size as the distribution pipe; for pipes larger than DN40, DN40 may be used provided that it is connected to the underside of the distribution pipe, and it is provided with a suitable plug.
Frequently Asked Questions
In which clause does EN 12845 describe the pressure test of the pipework?
The commissioning tests are in Clause 19.1.1 (EN p. 117). Clause 19.1.1.2 requires all installation pipework to be tested hydrostatically for at least 2 hours at not less than 15 bar or 1.5 times the maximum pressure to which the system will be subjected, whichever is the greater. Clause 19.1.1.1 additionally requires a pneumatic test for dry pipework: at least 2.5 bar for at least 24 hours, and any pressure loss greater than 0.15 bar in 24 hours is corrected. Clause 20.3 is the maintenance schedule, not a pressure test clause.
Which materials are recommended for underground pipe?
Clause 17.1.1 (EN p. 111): pipes are laid in accordance with the recommendations of the supplier and have adequate resistance to corrosion. The NOTE to the clause recommends the following pipe types: cast iron, ductile iron, spun cement, reinforced glass fibre and polyethylene high density. Adequate measures are also taken to prevent damage to the pipe, for example from the passage of vehicles.
Which pipe diameters cannot be welded on site?
Clause 17.1.3 (EN p. 111): pipes and fittings of less than 50 mm diameter shall not be welded on site unless the installer uses an automatic welding machine. In no case shall welding in position, flame cutting, brazing or any other hot work be carried out. In welding, all joints are continuously welded, the inside of the weld does not obstruct the water flow, and the pipe is free from burrs and slag. Welders are approved in accordance with EN ISO 9606-1.
At what spacing are pipe supports fitted?
Clause 17.2.2 (EN p. 113): supports are spaced no more than 4 m apart on steel pipe and 2 m apart on copper pipe. For pipes over 50 mm diameter these distances may be increased by 50 % provided that either two independent supports are fitted directly to the structure or a support is used that is capable of bearing a load 50 % greater than that called for in Table 40. Where mechanical pipe joints are used there is at least one support within 1 m of each joint and at least one support on each pipe section. The distance from a terminal sprinkler to a support shall not exceed 0.9 m for 25 mm diameter and 1.2 m for diameters greater than 25 mm; the distance from an upright sprinkler to a support shall not be less than 0.15 m.
What fall is required in dry, alternate and pre-action installations?
Clause 17.1.8 (EN p. 112): in dry, alternate and pre-action installations range pipes have a fall of at least 0.4 % towards the distribution pipe and distribution pipes a fall of at least 0.2 % towards the relevant drain valve. It is also ensured that all pipework can be drained; where a point cannot be drained through the drain valve at the control valve set, an additional valve is fitted in accordance with Clause 15.4, and range pipes are connected to distribution pipes only from the side or from the top.
Where may copper pipe be used in a sprinkler installation?
Clause 17.1.9 (EN p. 113): copper pipes may be used only in wet pipe systems, only in classes LH, OH1, OH2 and OH3, and only downstream of steel pipework. Joints are mechanical joints or brazed with fittings conforming to EN 1254; copper to steel joints are flanged with stainless steel bolts; the pipe shall not be bent on site and measures are taken against galvanic corrosion. Supports for copper pipe are provided with a suitable coating of adequate electrical resistance to prevent contact corrosion (Clause 17.2.1).
References
- TS EN 12845+A2:2026 Clause 3.78, 3.82 (EN p. 22)
- TS EN 12845+A2:2026 Clause 13.4.5, Table 36 (EN p. 103)
- TS EN 12845+A2:2026 Clause 15.6 (EN p. 109)
- TS EN 12845+A2:2026 Clause 17.1.1, 17.1.2, 17.1.3 (EN p. 111)
- TS EN 12845+A2:2026 Clause 17.1.4, 17.1.5, 17.1.6, 17.1.7, 17.1.8 (EN p. 112)
- TS EN 12845+A2:2026 Clause 17.1.9, 17.2.1, 17.2.2 (EN p. 113)
- TS EN 12845+A2:2026 Clause 17.2.3, Table 40, Table 41, 17.3.2 (EN p. 114)
- TS EN 12845+A2:2026 Clause 17.3.3 (EN p. 115)
- TS EN 12845+A2:2026 Clause 19.1.1.1, 19.1.1.2 (EN p. 117)
- TS EN 12845+A2:2026 Annex K (EN p. 159)
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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.