EN 12845 Pipe Supports and Hanger Spacing

The invisible detail holding up the sprinkler network: what spacing, what anchor, what clamp.

On an acceptance walk at a logistics warehouse, looking up, we found a DN100 distribution main hung between two steel trusses over a 4.5 m span from a single M10 threaded rod. Water-filled, the pipe masses about 13 kg per metre; the sag was visible to the naked eye. EN 12845 sets a maximum of 4 m for steel pipe; this project had 4.5 m and the exception condition — two independent supports, or a hanger 50 % stronger — had not been met. Pipe support is the one detail skipped because nobody looks at it, and the one that can bring the whole installation down the night it is charged with water.

The basic rule

The pipe support section has three parts: general principles, spacing and position, and design parameters. First the principles:

• Supports are fixed directly to the building, and where necessary to machinery, storage racking or another structure. No other service — ventilation, cable tray, lighting — may be hung from a sprinkler hanger.
• Hangers must be of the adjustable type, so load is distributed evenly rather than concentrated at one overloaded point.
• The clamp must fully encircle the pipe and must not be welded to the pipe or a fitting.
• Pipe above 50 mm may not be hung from profiled metal decking or aerated concrete; a load-bearing concrete or steel structure is required.
• No support component may be of combustible material, and nails may not be used.
• On copper pipe, an electrically insulating liner goes inside the clamp to prevent galvanic corrosion.

Hanger spacing — a one-line rule, not a table

EN 12845 does not give a row-by-row table by diameter the way NFPA 13 does. It sets a single rule:

• Steel pipe: maximum 4 m spacing.
• Copper pipe: maximum 2 m spacing.
• Pipe above 50 mm: spacing may be increased by 50 % — 6 m for steel, 3 m for copper — provided one of two conditions is met:
  • Two independent supports fixed directly to the structure, or
  • A single support capable of carrying 50 % more than the tabulated load capacity.

In practice this summary works:

Pipe	DN	Standard spacing	With the 50 % exception
Steel	≤ 50 mm (DN25–DN50)	4.0 m	—
Steel	DN65–DN100	4.0 m	6.0 m
Steel	DN125–DN200	4.0 m	6.0 m
Copper	≤ 50 mm	2.0 m	—
Copper	> 50 mm	2.0 m	3.0 m

The copper difference comes from deflection: copper's modulus of elasticity is about a third of steel's, so it sags twice as fast under the same load.

Extra rules for mechanically jointed pipe

Grooved couplings are common on steel pipe, and the standard adds two conditions for mechanical joints:

• At least one support within 1 m of every grooved joint.
• At least one support on every pipe length — a length with no support between two couplings is not acceptable.

Grooved pipe is less rigid between lengths than welded pipe; with no hanger, a turning moment develops at the coupling and the gasket leaks. So the 6 m exception is rarely applied on a grooved system — staying at 4 m is the safe practice.

Terminal sprinklers and the last support

An overlooked part of the clause is the sprinkler-to-support distance:

• On DN25 pipe: no more than 0.9 m from the end sprinkler to the last support.
• Above DN25: no more than 1.2 m.
• On upright sprinklers: at least 0.15 m between support and sprinkler. Closer than that, the hanger clamp obstructs the deflector pattern.

Additional support for vertical pipe

Vertical pipes must be supported as well as horizontal runs. Two limits apply:

• Additional support for vertical pipes longer than 2 m.
• Additional support for drops over 1 m feeding a single sprinkler.

Low-level pipes at risk of forklift impact are separately supported; two exceptions apply — horizontal sprinkler connections under 0.45 m and vertical drops or risers under 0.6 m are exempt.

Design: hanger capacity and anchor size

The load capacity, cross-sectional area and anchor embedment of hanger components come from a table:

Nominal pipe diameter	Min. load capacity (20 °C)	Min. threaded section	Min. anchor embedment (concrete)
d ≤ 50 mm	200 kg	30 mm² (M8)	30 mm
50 < d ≤ 100 mm	350 kg	50 mm² (M10)	40 mm
100 < d ≤ 150 mm	500 kg	70 mm² (M12)	40 mm
150 < d ≤ 200 mm	850 kg	125 mm² (M16)	50 mm

Three notes are critical:

1. Load capacity must not fall by more than 25 % when the material is heated to 200 °C — so the hanger does not sag during a fire.
2. The threaded rod section must meet the values above after the thread is cut. M10 is nominally 78 mm² but 52 mm² at the thread root — very close to the limit.
3. The embedment depths are for concrete; in aerated or lightweight concrete and in brick, the manufacturer's table differs and usually requires 1.5 to 2 times the depth.

A second table gives minimum flat bar and clamp dimensions:

Pipe diameter	Flat bar (galvanised)	Flat bar (black)	Clamp (galvanised)	Clamp (black)
d ≤ 50 mm	2.5 mm	3.0 mm	25 × 1.5 mm	25 × 3.0 mm
50 < d ≤ 200 mm	2.5 mm	3.0 mm	25 × 2.5 mm	25 × 3.0 mm

Galvanised material may be thinner because the corrosion allowance has been removed; black or ungalvanised material loses section over time and so is required thicker at the start. In humid ceiling voids — kitchens, wet areas — ungalvanised steel hangers are normally rusty within five years; stainless hangers should be specified around pools, laundries and near-freezing stores.

Fire resistance and materials

No support component may be combustible. That effectively rules out plastic anchors, timber packers and nylon ties. In a fire, flame melts the plastic anchors first, the hanger drops, the pipe breaks and the system is out of service. Field practice:

• Galvanised steel threaded rod with a galvanised clamp in dry areas.
• 304 stainless in humid, chlorinated or external locations.
• Concrete anchors: steel expansion anchors. Plastic-sleeved anchors are not accepted on sprinkler work.
• Steel beam connections: beam clamps.

Seismic bracing — the gap in EN 12845

EN 12845 does not regulate seismic bracing. That is the most critical subject the European standard leaves outside its scope. In Turkish seismic zones, leaving a sprinkler network on vertical hangers alone conflicts with the BYKHY requirement that the system be operable during and after an event. What is done in practice:

• Sway bracing to NFPA 13 principles on distribution mains (DN65 and above).
• Four-way bracing: diagonal braces in the horizontal and vertical planes. Longitudinal braces at up to 12.2 m along the pipe axis, lateral braces at up to 9.1 m.
• Restraint against vertical displacement on range pipes over 7.6 m.
• FM Global data sheets are stricter, requiring seismic support on all pipe above DN50.

The subject is under discussion at CEN; some countries use a national seismic annex alongside EN 12845. Turkey has no official fire seismic standard yet, so NFPA 13 is taken as the reference.

A field error: unhung pipe inside a plasterboard ceiling

During a hotel conversion, a DN50 sprinkler branch running inside the plasterboard suspended ceiling had been fixed to the ceiling profiles with plastic clips. There was no structural hanger at all. When the suspended ceiling collapsed in an earthquake, the pipe went down with it and water ran for 40 minutes until the main valve was shut. Two causes:

1. The pipe was invisible inside the ceiling, so site supervision could not check it.
2. A plasterboard profile is not a "structure" in EN 12845 terms and cannot carry sprinkler pipe. A ceiling profile does not have 200 kg of load capacity.

The correct arrangement: an M10 anchor into the concrete above, threaded rod and clamp; the ceiling profile carries only the sprinkler escutcheon.

Comparison with NFPA 13 hanger spacing

NFPA 13 gives hanger spacing in a detailed table by pipe diameter. In summary:

Pipe diameter	NFPA 13 max.	EN 12845 max.
1" / DN25	3.7 m (12 ft)	4.0 m
1¼" / DN32	3.7 m	4.0 m
1½"–2" / DN40–DN50	4.6 m (15 ft)	4.0 m
2½"–8" / DN65–DN200	4.6 m	4.0 m (6.0 m with the exception)

NFPA is tighter at small diameters (3.7 m) and looser at large ones (4.6 m). EN 12845 gives a single spacing of 4 m and opens an exception for larger pipe. NFPA additionally covers seismic bracing comprehensively; that is where EN 12845 is silent.

Turkish context

BYKHY requires sprinkler installations to comply with EN 12845 or NFPA 13 and delegates the hanger detail to the standard. In practice the fire authorities ask for compliance with the EN 12845 support clause and its capacity table at permit stage. Seismic bracing is not a permit condition, but under the mechanical services anchorage provisions of the seismic code, consultants increasingly require NFPA sway bracing.

Checklist — before going to site

• Any steel pipe spacing above 4 m? If so, is the exception documented?
• Any copper pipe spacing above 2 m? Is the insulating liner inside the clamp?
• Is there a support within 1 m of every grooved coupling?
• Terminal sprinkler to last support: ≤ 0.9 m on DN25, ≤ 1.2 m above?
• Additional support on vertical pipe over 2 m?
• Is any DN50+ pipe hung from plasterboard or metal decking? It must not be.
• Anchors: steel expansion type, correct M8/M10/M12/M16 size, 30/40/50 mm embedment in concrete?
• Any plastic anchors or nylon ties? There must be none.
• In a seismic zone, is there a sway bracing plan for the mains?

Frequently asked questions

What is the maximum hanger spacing on steel pipe?

4 m. Above 50 mm it can be increased by 50 % to 6 m, provided two independent supports are used or a single support carrying 50 % more than the tabulated load.

Why is copper spaced more closely?

Copper's modulus of elasticity is lower than steel's, so it deflects faster. The maximum is 2 m, rising to 3 m above 50 mm with the 50 % exception. An insulating liner is also required inside the clamp to prevent galvanic corrosion.

How far can the last support be from the end sprinkler?

0.9 m on DN25 pipe and 1.2 m above DN25. An upright sprinkler must be at least 0.15 m from the support, otherwise the discharge pattern is disturbed.

Does EN 12845 require seismic bracing?

No, it does not address it. In seismic regions, NFPA 13 sway bracing practice or the FM Global data sheets are used instead, added by the designer's own decision.

When does a vertical pipe need additional support?

Above 2 m in general, and above 1 m for a drop feeding a single sprinkler. Low-level pipe exposed to mechanical impact is separately supported, though horizontal connections under 0.45 m and vertical drops under 0.6 m are exempt.

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