EN 12845 Zone Test and Drainage Facilities: Clauses 15.4, 15.5 and Annex D.3.5

Source: TS EN 12845+A2:2026, Clause 15.4 and Table 39 (EN p. 107-108), Clause 15.5 (EN p. 108-109) and Annex D (EN p. 136-138).

EN 12845 does not gather "zone test and drainage facilities" into a single clause. The subject sits in three places: general drain valves in Clause 15.4 with Table 39, test valves in Clause 15.5, and the test and drainage facility specific to zoned installations in Annex D.3.5. The fall requirement for pipe drainage is in Clause 17.1.8.

One correction has to come first: Clause 16.3 is not a drainage clause. The title of 16.3 is "Fire brigade and remote central station alarm connection" (EN p. 111).

Clause 15.4: drain valves

Drain valves are fitted as specified in Table 39 to allow drainage from the pipework as follows:

• a) immediately downstream of the control valve set or of its downstream stop valve if fitted;
• 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 any subsidiary stop valve installed for testing;
• e) any pipe, with the exception of drop pipes to single sprinklers in a wet installation, which cannot be drained through another drain valve.

The valves are fitted at the lower end of the pipework and sized as specified in Table 39. The outlet shall be no more than 3 m above the floor and shall be fitted with a suitable plug.

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

The largest value in the table is 50 mm. The standard does not define drainage capacity as a percentage of the design flow; Clause 15.4 gives only diameters and locations.

Clause 17.1.8: pipe drainage and fall

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 (EN p. 112). The NOTE to the clause states that in cold climates where severe freezing is possible it may be necessary to give wet systems a fall as well, and to increase the fall in dry systems. Range pipes are connected to distribution pipes only from the side or from the top.

The standard contains no distance based drainage rule (such as "a low point drain every X metres"). The need for a drain valve is determined by whether the pipe is trapped and by the list a) to e) in Clause 15.4.

Clause 15.5: test valves

15.5.1 Alarm and pump set start test valves

15 mm test valves are fitted as appropriate to test the following:

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

15.5.2 Remote test valves

A test facility comprising a test valve with the associated fittings and pipework is provided. This facility gives a flow equivalent to the discharge of a single sprinkler and is connected to the hydraulically most remote point of a distribution pipe (EN p. 109).

The functional counterpart of this valve is in Clause 11.2.2: the maximum time between a single sprinkler opening and water discharging shall 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 (EN p. 67): 90 s for LH; 60 s for OH and HH.

Flow switch test connection

Clause 16.2.2 (EN p. 110): water flow alarm switches are used only in wet installations. A test connection that simulates the operation of a single sprinkler is fitted downstream of each switch, and that connection is provided with a drain. The pressure and flow characteristic of the fully open test valve and the draw off pipe is equal to that of the smallest nominal size sprinkler fed from the flow switch. Any orifice plate is located at the pipe outlet and is of stainless steel or non-ferrous material. The outlet of the test pipe is positioned relative to the drainage system so that the water flow can be seen during the test.

Annex D: test and drainage in zoned installations

Annex D is normative but its field of application is narrow: wet pipe OH sprinkler installations only (D.1, EN p. 136). Zoning is optional unless required elsewhere in the standard.

D.2 constraints: the protected floor area controlled by one wet control valve set on a single floor shall not exceed 12 000 m²; the installation is zoned in accordance with D.3; zoned installations shall not contain a hazard greater than OH3; car parks and goods unloading and storage areas are on a separate, unzoned installation; the building is sprinkler protected on all floors; and the protected floor area controlled by a single control valve set shall not exceed 120 000 m².

D.3.1: the protected floor area per zone shall not be greater than 6 000 m².

D.3.2: each zone is controlled independently by a single zone subsidiary stop valve fitted in a readily accessible position at the floor level of the zone it controls; each valve is secured in the open position and labelled to indicate the area of protection it controls.

D.3.3: each zone is provided with a valve of nominal size not less than 20 mm, fitted at the end of the distribution pipe hydraulically most remote from the water supply or, where appropriate, at the end of each distribution pipe branch. The valve outlet is provided with a brass plug cap.

D.3.4: zoned installations are provided with tamper resistant devices that monitor whether each stop valve (including subsidiary stop valves) is fully open, the water flow into the zone immediately downstream of each zone subsidiary stop valve (by means of a water flow alarm switch capable of detecting a flow equal to or greater than that from a single sprinkler), and the water flow through each main installation control valve set.

D.3.5 Zone test and drainage facilities: permanent test and drainage facilities are provided in each zone immediately downstream of the water flow alarm switch. The test facility shall simulate the operation of any single sprinkler head. Adequate provision is made for the removal of waste water.

D.3.6: the control valve set of a zoned installation comprises a single alarm valve with a stop valve on each side of it and a bypass connection around these three valves fitted with a normally closed stop valve of the same nominal size. Each of the three stop valves is provided with a tamper resistant monitoring device.

D.3.7: the monitoring devices are connected to a control and indicating panel. Among the indications to be given at the panel is an audible device and an amber visual indication if the static pressure in any trunk main feeding the system falls 0.5 bar or more below the normal static pressure. For zoned installations the block plan also shows the locations of the zone control valves (D.4).

Removal of test water and other test points

• Clause 8.5.3 (EN p. 45): provision is made for the removal of test water. Dry or alternate control valve sets (main or subsidiary) may include an additional flow test valve arrangement fitted below the control valve set, downstream of the main stop valve; that valve and pipework is of nominal size 40 mm in LH installations and 50 mm in other installations.
• Clause 10.3.2 (EN p. 58): in the sprinkler protection of the pump room, a drain and test valve of 15 mm nominal size that allows a practical test of the alarm system is fitted downstream of the flow alarm.
• Clause 20.2.2.3 (EN p. 119): in the weekly routine each water motor alarm is sounded for at least 30 s. This is not a requirement for a flow switch to be triggered within a given time.

Field note: the text of EN 12845 contains no separate provision for a fire brigade connection. The only mention is the NOTE to Table 8 (EN p. 44): an additional supply arrangement with a non-return valve may be provided for the fire brigade. The drainage, testing or maintenance regime of that arrangement is not defined in the standard.

Frequently Asked Questions

Where does EN 12845 give the sizes of drain valves?

Clause 15.4 and Table 39 (EN p. 107-108). Table 39 gives the minimum drain valve and pipe diameters as follows: LH installation 40 mm; OH, HHP or HHS installation 50 mm; subsidiary installation 50 mm; a zone 50 mm; trapped distribution pipes of diameter equal to or less than 80 mm 25 mm; trapped distribution pipes of diameter greater than 80 mm 40 mm; trapped range pipes 25 mm; trapped pipework between a dry or subsidiary alarm valve and a subsidiary stop valve installed for testing purposes 15 mm. Clause 16.3 is not a drainage clause; 16.3 is the fire brigade and remote central station alarm connection (EN p. 111).

Where and at what height is a drain valve fitted?

Clause 15.4 (EN p. 107-108): drain valves are fitted immediately downstream of the control valve set (or of its downstream stop valve if fitted); immediately downstream of any subsidiary alarm valve; immediately downstream of any subsidiary stop valve; between a dry pipe or subsidiary control valve set and any subsidiary stop valve installed for testing; and on any pipe which cannot be drained through another drain valve, with the exception of drop pipes to single sprinklers in a wet installation. The valves are fitted at the lower end of the pipework, the outlet is no more than 3 m above the floor and it is fitted with a suitable plug.

What does a remote test valve do?

Clause 15.5.2 (EN p. 109): a test facility comprising a test valve with the associated fittings and pipework is provided; this facility gives a flow equivalent to the discharge of a single sprinkler and is connected to the hydraulically most remote point of a distribution pipe. Clause 11.2.2 states that in dry and alternate installations the maximum water delivery time test is carried out with this valve; according to Table 18 the time is 90 s for LH and 60 s for OH and HH (EN p. 67).

Where are the test and drainage facilities in a zoned installation?

Annex D.3.5 (EN p. 137): permanent test and drainage facilities are provided in each zone immediately downstream of the water flow alarm switch. The test facility shall simulate the operation of any single sprinkler head. Adequate provision is made for the removal of waste water. Annex D applies only to wet pipe OH installations (D.1) and the protected floor area per zone shall not exceed 6 000 m² (D.3.1).

For how long is the water motor gong sounded?

Clause 20.2.2.3 (EN p. 119): in the weekly routine each water motor alarm is sounded for at least 30 seconds. This is not a requirement for a flow switch to be triggered within a given time; the standard gives no numerical response time for a flow alarm.

What size are the alarm and pump start test valves?

Clause 15.5.1 (EN p. 108): 15 mm test valves are fitted as appropriate. They test the hydraulic alarm and the electric alarm pressure switch by drawing water from immediately downstream of the wet alarm valve and its downstream main stop valves, or of the alternate alarm valve; the same alarms by drawing water from downstream of the main water supply stop valve and upstream of the alternate, dry pipe or pre-action alarm valve; any water flow alarm switch fitted downstream of the control valve set, by drawing water from downstream of the flow alarm; the automatic pump set starting device; and any pump or pressure tank room sprinkler alarm flow switch fitted upstream of the control valve set.

References

• TS EN 12845+A2:2026 Table 8 and its NOTE (EN p. 44)
• TS EN 12845+A2:2026 Clause 8.5.3 (EN p. 45)
• 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 15.4 (EN p. 107-108)
• TS EN 12845+A2:2026 Table 39, Clause 15.5.1 (EN p. 108)
• TS EN 12845+A2:2026 Clause 15.5.2 (EN p. 109)
• TS EN 12845+A2:2026 Clause 16.2.2 (EN p. 110)
• TS EN 12845+A2:2026 Clause 16.3 (EN p. 111)
• TS EN 12845+A2:2026 Clause 17.1.8 (EN p. 112)
• TS EN 12845+A2:2026 Clause 20.2.2.3 (EN p. 119)
• TS EN 12845+A2:2026 Annex D.1, D.2, D.3.1-D.3.7, D.4 (EN p. 136-137)

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