EN 12845 Drain, Test and Flushing Valves

Keeping an installation healthy depends on a few small valves — and the standard states exactly where they go, at what size, on what interval and in what sequence.

Arriving for annual maintenance at a logistics warehouse, we opened the DN50 drain valve downstream of the alarm valve; some water came, some did not. The cause was simple: the drain line ended 50 mm above the floor, and hardened limescale and corrosion flakes had built up below. The main drain had not been opened in six years. Weekly tests through the DN15 alarm test valve had been signed off as satisfactory, but the installation had never really been observed or flushed. This article covers the drain, test and flushing valves from a site perspective.

Four separate valves, four separate purposes

EN 12845 collects control valve set accessories under one clause and separates four groups. The distinction matters, because on site "test valve" usually means only the alarm test valve, while the standard separates four jobs:

• Drain valves: for emptying the installation. No flow requirement; the system is drained for maintenance or repair.
• Alarm and pump start test valves: fixed at DN15, to prove the alarm circuit and automatic pump start. They simulate operation of a single sprinkler, but the hydraulic characteristic does not matter.
• Remote test valves: at the hydraulically most remote point, simulating the actual discharge of one sprinkler. The real hydraulic performance test.
• Flushing connections: at the ends of distribution pipe spurs, to expel sediment.

In zoned buildings, the zoning annex adds requirements for a zone flushing valve (at least DN20 at the most remote point, with a brass plug) and permanent zone test and drainage facilities immediately downstream of the zone flow alarm switch.

Main and auxiliary drain valves

Drain valves are required at:

• Immediately below the control valve set or the downstream stop valve;
• Immediately below a subsidiary alarm valve;
• Immediately below a subsidiary stop valve;
• Between a dry or subsidiary valve set and any subsidiary stop valve fitted for testing;
• Any pipe run, other than a drop to a single sprinkler, that cannot be drained through another drain.

The position rule: the drain valve sits at the lowest point of the pipe, with the outlet no more than 3 m above the floor, closed with a suitable plug. The outlet is not left open; a plug is required to protect people nearby and to keep it dry. On site the main drain is often left 4–5 m up, so maintenance works from a ladder, the discharge does not travel far, and freezing problems appear in the internal drain channel. The 3 m limit was written deliberately.

The term "auxiliary drain" does not appear directly, but the requirement for any pipe that cannot be drained through another valve covers, in practice, the small DN15–25 drum drips at the low points of dry installations. On dry and alternate systems these fall within the weekly check; if water arrives ahead of air, they are drained here.

Drain valve sizes

What the drain valve empties	Min. size (DN, mm)
Light hazard installation	40
OH / HHP / HHS installation	50
Subsidiary installation	50
Zone	50
Trapped distribution pipe, ≤ DN80	25
Trapped distribution pipe, > DN80	40
Trapped range pipe	25
Between dry/subsidiary alarm valve and subsidiary stop valve, for testing	15

Alarm and pump start test valves (fixed at DN15)

The 15 mm test valves are used to prove:

• The hydraulic gong alarm and electrical pressure switch, by drawing water downstream of a wet, alternate, dry or pre-action alarm valve;
• Any flow alarm switch downstream of the control valve set, by simulating flow;
• The automatic pump starting device;
• Any sprinkler alarm flow switch in a pump or pressure tank house upstream of the control valve set.

The valve is deliberately DN15, because its only purpose is to operate the alarm circuit. It simulates the 60–100 L/min from a single sprinkler and needs no more. The label beside it is explicit: "ALARM TEST", and the standard requires that label to be hung there.

Remote test valves

This is the most confused item. The remote test valve sits at the hydraulically most remote point and simulates the actual discharge of one sprinkler, taking the K-factor and all pipe friction losses into account. Fully open, its pressure-flow characteristic must equal that of the smallest nominal sprinkler behind the flow switch. The orifice plate goes at the outlet end, in stainless steel or a non-ferrous material.

Its purpose is to prove both the hydraulics and the alarm response time: alarm activation must occur within 60 seconds of the remote test valve being opened. In large gridded systems that time is easily exceeded, through either pipe size or a sticking alarm valve clapper.

Flushing connections

These go at the ends of distribution pipe spurs. The sizing rule: the same size as the distribution pipe, or DN40 where the pipe exceeds DN40, provided the connection is on the underside. A suitable plug is fitted. Range pipe ends can also be arranged as blank tees — practical in gridded layouts for venting the air pockets that lengthen alarm times.

The standard notes that a completely water-filled pipe may be damaged by pressure rise from a temperature increase. Where the installation cannot be fully vented — gridded pipework with flushing connections at the extremities — a pressure relief valve should be considered. So the secondary role of a flushing connection is passive protection against air pockets.

Which valve is tested when

Interval	Valve / test
Weekly (max. 7 days)	Water motor alarm test for at least 30 s, via the alarm test valve
Weekly	Automatic pump start test, dropping pressure by fully opening the drain and test valve
Quarterly (max. 13 weeks)	Operate every stop valve closed and open; check flow alarms
Annually (max. 12 months)	Full-load pump flow test through the test line connection
Annually	Zone test — open the most remote test valve for hydraulic verification, per zone in zoned systems

In installations with the enhanced reliability provisions and zoning, when a zone is closed for maintenance the flushing valve is opened before the zone is refilled, to confirm water has reached it. That small operation prevents the "valve opened but the line is still dry" error, and it should be recorded.

Field error: a blocked zone test connection

A case that recurs at annual maintenance: the zone test line orifice — typically 2.8 to 5.6 mm, simulating a K57 or K80 sprinkler — is blocked. The reasons:

• Microbiologically influenced corrosion and flake corrosion: the layer inside galvanised pipe sheds on first flow and lodges at the orifice mouth. Dry and alternate installations are most vulnerable.
• Construction debris: PTFE tape, fibre and adhesive left inside during installation. Without flushing after the hydrostatic test, it blocks here.
• Limescale: in hard water regions, scale builds up inside a line that has not flowed for years.
• Wrong orifice material: the standard requires stainless or non-ferrous; where black steel is used, corrosion products quickly close the orifice.

Prevention has four stages: specify a stainless or bronze orifice at design; place the flushing connection ahead of the orifice so sediment can be cleared without opening it; open the flushing connection first at the annual test and run water for a minute or two; and record alarm activation time before and after flushing separately in the logbook. A large difference between the two means the orifice is silting up.

Comparison with NFPA 25

NFPA 13 sets the installation rules — test connection, main drain, auxiliary drain — while NFPA 25 covers inspection, testing and maintenance. EN 12845 combines both in one standard. Comparing:

• Main drain test: quarterly under NFPA 25 (investigate if residual pressure drops more than 10 %); EN 12845 sets no separate interval but exercises it within the quarterly stop valve tests.
• Inspector's test connection: NFPA 13 places it beside the end sprinkler with the smallest K orifice; the EN 12845 remote test valve is its equivalent. Same logic, different name.
• Annual main drain test: annual under NFPA 25; EN 12845 achieves the same through the annual full-load flow test.
• Sizes: NFPA main drain 2 in (DN50); EN 12845 DN40 for light hazard and DN50 for all others. Practically identical.

Both standards follow the same logic: know what the valve you open is simulating, record pressure and flow, compare annually, and investigate if the trend falls.

Turkish context

BYKHY requires sprinkler installations to be designed to EN 12845 or NFPA 13, and requires operating and maintenance instructions — for which the EN 12845 maintenance clauses or NFPA 25 provide the detail. At site inspections, the fire service or insurance surveyor almost always asks for the logbook and the weekly alarm test records; without them, the system is marked as inadequately maintained even where the drain and test valves are physically present. Adding a line to the mechanical specification requiring valves, labels and a logbook in accordance with the relevant clauses ends the argument on new projects.

Common errors

• Leaving the main drain outlet more than 3 m above floor level.
• Connecting the drain line directly to foul drainage — back-pressure and contamination risk; an air gap is required.
• No label beside the alarm test valve.
• A remote test valve orifice made from galvanised or black steel.
• Omitting flushing connections on aesthetic grounds.
• Leaving zone test and drainage discharge uncontrolled on site — adequate waste water disposal is required.
• Not checking drum drips on a dry installation before the freezing season — water collects, freezes and splits the pipe.

Closing

Drain, test and flushing valves are small details that decide the future on site. Selecting the right size and material at design stage, labelling them, and drilling the operating team on the routine — 30 seconds weekly, a stop valve round quarterly, a flow test annually — is the cheapest investment you can make toward an alarm sounding twenty years from now.

Frequently Asked Questions

What is the difference between an alarm test valve and a remote test valve?

The DN15 alarm test valve only proves the alarm circuit and pump start. The remote test valve sits at the hydraulically most remote point and simulates the real discharge of one sprinkler, proving the hydraulics.

How high may a drain outlet be?

No more than 3 m above the floor, at the lowest point of the pipe and closed with a suitable plug. Leaving it 4–5 m up makes maintenance impractical.

What size must drain valves be?

DN40 for light hazard and DN50 for ordinary and high hazard installations and zones, with DN25 to DN40 for trapped pipework depending on size.

Why do zone test orifices block?

Corrosion flakes, construction debris and limescale — and a wrongly specified black steel orifice. Specify stainless or bronze, and flush ahead of the orifice before every annual test.

SprinkCalc — Fire Sprinkler Design Across Three Standards

SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.

Download SprinkCalc on the App Store

MEP Calc — 86+ Engineering Calculators

MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.

Download MEP Calc on the App Store