EN 12845 Drain, Test and Flushing Valves (Clauses 15.4-15.6)

Drain, test and flushing connections are covered in three separate subclauses of EN 12845, all three under Clause 15 "Valves". These three items determine both the commissioning and the maintenance capability of an installation; almost every maintenance routine runs through these valves. Source: TS EN 12845+A2:2026, Clauses 15.4-15.6, EN p.107-109.

Drain valves: where and at what size

Clause 15.4 (EN p.107) requires drain valves to be sized in accordance with Table 39 and to be located at the following points:

• a) immediately downstream of the control valve set or, where fitted, of the stop valve downstream of it;
• b) immediately downstream of any subsidiary alarm valve;
• c) immediately downstream of any subsidiary stop valve;
• d) between a dry pipe or subsidiary control valve set and a subsidiary stop valve fitted for test purposes;
• e) on every pipe in a wet installation, other than drop pipes to single sprinklers, which cannot be drained through another drain valve.

The valves are fitted at the lower end of the pipework. The outlet is not more than 3 m above floor level and is closed with a suitable plug (EN p.108).

Table 39: Minimum size of drain valves (EN p.108)

The provision to be read together with Table 39 is Clause 17.1.8 (EN p.112): arrangements are made so that all pipework can be drained; where this cannot be done through the drain valve at the control valve set, additional valves conforming to 15.4 are fitted. The same clause requires that, in dry, alternate and pre-action installations, range pipes be laid with a fall of at least 0.4 % towards the distribution pipe and distribution pipes with a fall of at least 0.2 % towards a suitable drain valve. These values are percentages, not degrees. Range pipes are connected to distribution pipes only from the side or from above.

Test valves

15 mm alarm and pump starting test valves (15.5.1, EN p.108)

15 mm test valves are fitted in suitable locations so that the following can be tested:

• a) the hydraulic alarm and, where fitted, the electric alarm pressure switch, by drawing water immediately downstream of: the wet alarm valve and the main stop valves downstream of it; the alternate alarm valve;
• b) the hydraulic alarm and, where fitted, the electric alarm pressure switch, by drawing water downstream of the main water supply stop valve and upstream of: the alternate alarm valve, the dry pipe alarm valve, the pre-action alarm valve;
• c) the water flow alarm switch fitted downstream of the control valve set, by drawing water downstream of the flow alarm;
• d) the automatic pump set starting device;
• e) the pump or pressure tank room sprinkler alarm flow switch fitted upstream of the control valve set.

Two further provisions are related to this. Clause 10.3.2 (EN p.58) requires, in the sprinkler protection of a pump compartment, that a drain and test valve of 15 mm nominal size be fitted downstream of the flow alarm so that the alarm system can be tested practically. Clause 16.2.2 (EN p.110) states that water flow alarm switches may only be used on wet installations and that a test connection with a drain, simulating the operation of a single sprinkler, shall be fitted downstream of each switch: the draw off pipe is galvanized steel or copper; the pressure/flow characteristic of the fully open test valve with the draw off pipe is equal to that of the smallest nominal size sprinkler supplied from the flow switch; any orifice plate is located at the pipe outlet and is made of stainless steel or non ferrous material. The test pipe outlet is positioned with respect to the drainage system so that the water flow can be seen during tests.

Remote test valve (15.5.2, EN p.109)

A test facility is provided: it comprises the test valve together with the associated fittings and pipework, gives a flow equivalent to the discharge of a single sprinkler, and is connected to the hydraulically most remote point of a distribution pipe.

The main function of this valve is to measure the water delivery time of dry and alternate installations. Clause 11.2.2 (EN p.67): the maximum time between the opening of a single sprinkler and the discharge of water does not exceed the value in Table 18, and the test is carried out using the remote test valve specified in 15.5.2.

Table 18: Maximum water delivery time, dry and alternate installations (EN p.67)

The note to the same clause states that, with an accelerator, volumes not exceeding 4 m³ for LH or OH and 3 m³ for HH occupancies are expected to satisfy the requirement of 11.2.2. The standard gives no other limit on installation volume.

There is another 60 second provision in the standard which should not be confused with this one: Clause 11.4.1.4 b) (EN p.69) requires that, where a sprinkler system contains more than one pre-action installation and simultaneous filling can occur, the time between the tripping of those installations and the discharge of water from any remote test valve does not exceed 60 seconds. That is not the alarm time measured from the opening of a single sprinkler.

Flushing connections (15.6, EN p.109)

• Flushing connections, with or without permanent valves, are fitted at the spur ends of the installation distribution pipes.
• Flushing connections are of the same size as the distribution pipe. On pipes larger than DN40, a DN40 flushing connection may be used provided it is connected to the underside of the distribution pipe.
• It is closed with a suitable plug.
• Flushing connections in the form of a blind tee on range pipes may be required in some cases.
• Apart from the periodic flushing of pipework, flushing connections may also be used to verify that water is available and to carry out pressure and flow tests.
• Pipework that is completely full of water may be damaged by a pressure rise due to a temperature increase. Where complete venting of air from an installation is possible, for example in a gridded arrangement with flushing connections at the ends, the fitting of a pressure relief valve should be considered.
• Note: excessive trapped air in a wet pipe installation can lead to an unacceptable alarm activation time and can create hydraulic imbalance in gridded pipe arrangements.

Drain, test and flushing in zoned installations

Zoned OH wet installations are covered in Annex D (normative, EN p.136-137).

Clause D.3.5 requires a permanent facility; it does not define the interval at which this test is to be carried out. The intervals are in Clause 20.

Annex F.8 (EN p.144), in setting out additional precautions during maintenance, gives the flushing valve an explicit task: when a zone (or zones) has been drained and is refilled with water, the flushing valve or valves of D.3.3 are used to check that water is available in the zone. The same clause requires that only one zone at a time be taken out of service in a multi zone installation.

Maintenance intervals in which these valves appear

The sign next to the alarm test valve

Clause 18.2.6.1 (EN p.116): where a flow of water into an installation initiates an automatic alarm to the fire service, a sign stating this is fixed adjacent to the alarm test valve or valves.

The standard defines no wording, colour or letter height for this sign. The signs with defined colour and letter size within Clause 18 are others: 18.2.1 the location plate ("SPRINKLER STOP VALVE" at least 35 mm, "INSIDE" at least 25 mm, white on a red background), 18.2.2 the stop valve sign ("SPRINKLER CONTROL VALVE", white letters at least 20 mm, red background; inside the door, "Keep door locked" in white letters at least 5 mm on a blue background), 10.8.3.2 and 18.2.6.3 the electricity supply switch label (at least 10 mm, white on a red background). There is no subclause 18.3 under Clause 18.

Clause 18.2.7 (EN p.117) sets the general rule: all valves and instruments used in testing and operating the system are suitably labelled and the corresponding identification appears in the documentation. This provision requires every drain, test and flushing valve in an installation to be identified by the same number on the drawings and on site.

Field note: the standard does not regulate how the drain outlet is to be connected to the waste water installation, the diameter of the test orifice plate or the need for an air gap. These details are resolved with local plumbing legislation and equipment supplier data.

Frequently Asked Questions

What are the drain valve sizes in EN 12845?

TS EN 12845+A2:2026 Table 39 (Clause 15.4, EN p.108): LH installation 40 mm; OH, HHP or HHS installation 50 mm; subsidiary installation 50 mm; a zone 50 mm; trapped distribution pipe 25 mm where the diameter is 80 mm or smaller and 40 mm where it is greater than 80 mm; trapped range pipes 25 mm; trapped pipework between a dry or subsidiary alarm valve and a subsidiary stop valve fitted for test purposes 15 mm. The valve is fitted at the lower end of the pipework, its outlet is not more than 3 m above floor level and it is closed with a suitable plug.

What size shall the alarm test valve be?

Clause 15.5.1 (EN p.108): 15 mm test valves are fitted. They serve to test the hydraulic alarm and, where fitted, the electric alarm pressure switch by drawing water immediately downstream of the wet alarm valve and the main stop valves downstream of it, and by drawing water upstream of alternate, dry and pre-action alarm valves. The water flow alarm switch downstream of the control valve set, the automatic pump set starting device and the sprinkler alarm flow switch of the pump or pressure tank room are also tested by the same 15 mm test valves.

What is a remote test valve for?

Clause 15.5.2 (EN p.109): it is a test facility connected to the hydraulically most remote point of a distribution pipe that gives a flow equivalent to the discharge of a single sprinkler. Clause 11.2.2 (EN p.67) requires the water delivery time test on dry and alternate installations to be carried out with this valve; according to Table 18 the time between the opening of a single sprinkler and the discharge of water does not exceed 90 seconds in LH and 60 seconds in OH and HH.

Where and at what size is a flushing connection fitted?

Clause 15.6 (EN p.109): flushing connections are fitted at the spur ends of the installation distribution pipes. They are of the same size as the distribution pipe; on pipes larger than DN40 a DN40 connection may be used provided it is connected to the underside of the distribution pipe. It is closed with a suitable plug. Flushing connections in the form of a blind tee on range pipes may be required in some cases.

Which sign is fixed next to the alarm test valve?

Clause 18.2.6.1 (EN p.116): where a flow of water into an installation initiates an automatic alarm to the fire service, a sign stating this is fixed adjacent to the alarm test valve or valves. The standard gives no specific wording, colour or letter height for this sign; Clause 18 contains 18.1 and 18.2, there is no 18.3.

References

• TS EN 12845+A2:2026 Clause 10.3.2 (EN p.58)
• TS EN 12845+A2:2026 Clause 11.2.2, Table 18 (EN p.67)
• TS EN 12845+A2:2026 Clause 11.4.1.4 b) (EN p.69)
• TS EN 12845+A2:2026 Clause 15.4, Table 39 (EN p.107-108)
• TS EN 12845+A2:2026 Clauses 15.5.1, 15.5.2, 15.6 (EN p.108-109)
• TS EN 12845+A2:2026 Clause 16.2.2 (EN p.110)
• TS EN 12845+A2:2026 Clause 17.1.8 (EN p.112)
• TS EN 12845+A2:2026 Clauses 18.2.1, 18.2.2, 18.2.6.1, 18.2.7 (EN p.115-117)
• TS EN 12845+A2:2026 Clauses 20.2.2.3, 20.2.2.4 (EN p.119)
• TS EN 12845+A2:2026 Clauses 20.3.2.5, 20.3.2.7, 20.3.2.8 (EN p.121)
• TS EN 12845+A2:2026 Clauses 20.3.4.2.1, 20.3.4.2.2 (EN p.122)
• TS EN 12845+A2:2026 Annex D, Clauses D.3.1, D.3.2, D.3.3, D.3.5 (EN p.136-137)
• TS EN 12845+A2:2026 Annex F, Clause F.8 (EN p.144)

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