Standards guide · Malleable iron fittings

Malleable iron fittings: EN 10242, threads to EN 10226-1 and selection

Malleable iron fittings – in the trade often searched for as cast iron fittings – are threaded fittings made of heat-treated ("malleablised") cast iron: the classic detachable pipe joint for gas, water, heating and compressed air. This page puts the standards EN 10242 and DIN 2950 in context, explains material, threads and thread sealing – and lists the most common GF type numbers with their EN symbols.

Choose the fitting number – name, symbol and shape

Dimensions, dimensional sketch and availability of every number – black and galvanized, with the link to our shop: dimensions by number.

Type no.	Designation	ISO/EN symbol
40	45° bend, long	G4/45°
90	90° elbow, equal	A1
92	90° elbow, equal	A4
120	45° elbow	A1/45°

Show full table · more than 10 rows

Common GF malleable iron fitting types with EN 10242 symbols (selection from the GF catalogue)
Type no.	Designation	ISO/EN symbol
40	45° bend, long	G4/45°
90	90° elbow, equal	A1
92	90° elbow, equal	A4
120	45° elbow	A1/45°
130	Tee, equal	B1
180	Cross, equal	C1
240	Socket, reducing	M2
241	Reducing nipple	N4
270	Socket	M2
280	Hexagon nipple	N8
290	Plug with rim	T9
300	Cap	T1
310	Backnut	P4
330	Union, flat seat	U1
340	Union, taper seat	U11
529a	Socket with female and male thread	M4

Range overview of GF malleable iron fittings: product photos of all common types from type 1 (90° bend) to type 933a, each with its GF type number — Range overview with GF type numbers – from bend type 1 to weld-on elbow type 933a. Image: Georg FischerChoose a type – dimensions and availability are listed by GF number.

Standard: EN 10242
Replaces: DIN 2950
Threads: R / Rp (EN 10226-1)
Working pressure: up to 25 bar (depending on medium/temperature)

GF malleable iron fittings in galvanised and black finish: sockets, tees, bends, crosses and unions with the cast-in +GF+ mark — GF malleable iron fittings in both finishes: galvanised (Zn) and black (Fe). Image: Georg Fischer

One of the largest GF malleable iron stocks in the German-speaking region: Zickwolff is an authorised Georg Fischer (GF) distributor and keeps one of the most comprehensive GF malleable iron stock ranges – including spare parts for maintenance of older installations. We deliver across Europe.

What are malleable iron fittings?

Malleable iron fittings are threaded fittings made of heat-treated ("malleablised") cast iron. The material combines the good castability of cast iron with steel-like toughness: complex fittings that nevertheless withstand high mechanical loads. Because components and threads are standardised throughout, an installation often remains extendable for decades – matching spare and extension parts are still available for many old installations, provided thread, dimension, material and approval match. This is exactly what makes malleable iron relevant for maintaining existing plants.

Galvanised 90° malleable iron bend with female thread and cast-in +GF+ trademark — 90° bend (type 2) with cast-in +GF+ mark – the trademark identifies the original. Image: Georg Fischer

Where aggressive media or outdoor use call for higher corrosion resistance, stainless steel threaded fittings are the alternative – with the same R/Rp thread interface.

Standards: EN 10242 replaces DIN 2950

The product standard is EN 10242 (related: ISO 49). It has replaced the national standards – in Germany DIN 2950. If you work with old parts lists or existing plants using DIN 2950 designations, EN 10242 provides the successor system (special case United Kingdom: BS 143 & 1256 partly remains in use). The material standard is EN 1562.

Reading a standard designation (example): Elbow EN 10242 – A1 – ½ – Zn – A = fitting type / product standard / fitting symbol / thread size / finish (Fe = black, Zn = galvanised) / thread version. In addition, manufacturers use type numbers (GF: type 1 bend, 90, 130, 340 … up to 933a) – in the trade the type numbers are the common ordering language, the EN symbols the tendering language.

The z-dimension. EN 10242 fixes the z-dimension of every fitting – the take-off from the centre to the pipe end in the thread, which the fitter deducts when cutting to length. For GF malleable iron fittings these dimensions have remained unchanged for decades, and the availability of the parts has proved itself over decades: whoever maintains or repairs a plant fits the spare part without making the pipe piece anew. What the z-dimension means for press systems, which are not standardised, and how it differs from the zeta value is explained on the press systems page.

Material: whiteheart malleable cast iron

GF manufactures from whiteheart malleable cast iron EN-GJMW-400-5 to EN 1562 (tensile strength 400 N/mm², elongation 5 %). Other standard grades: EN-GJMB-350-10 (blackheart), EN-GJMW-350-4. The raw casting is hard and brittle; only the malleablising heat treatment produces the tough, machinable final structure. Important in practice: malleable cast iron is not a welding material like steel – higher temperatures change the microstructure; joints are made by thread, not by weld. More on cast materials on the materials page.

Threads: the most frequently confused topic

EN 10226-1 – sealing in the thread (standard for malleable iron): taper external thread R into parallel internal thread Rp (or taper internal thread Rc to Part 2) – the metallic sealing pressure is created in the thread itself.

EN ISO 228-1 – G thread (do not confuse): parallel, not sealing in the thread – sealed with a washer on a shoulder face.

NPT (North American): its own taper angle and flank profile, not compatible with R/Rp despite similar appearance.
GF features: reinforced, free-running, corrosion-inhibiting internal threads; high angular and dimensional accuracy (precise pipe runs, high metallic sealing pressure).

Most common mistake: mixing NPT, G and Rp/Rc – it looks right, but it never seals permanently.

The matching threaded pipes to EN 10255 (formerly DIN 2440/2441) are covered on the pipes page.

Thread sealing

Hemp + jointing paste: well proven for R/Rp metal threads; sealant to EN 751. Mistakes: too much hemp, contamination; unsuitable for oxygen.
PTFE tape: with a standard right-hand thread, wind in the screwing-in direction so the tape does not unwind; number of layers and free thread turns per manufacturer's instructions. Mistakes: tape residues in the system, wrong winding direction.
Anaerobic sealants: cure between metal faces in the absence of air; limits with inactive materials (e.g. stainless steel without activator) and large gaps.
Always select by medium, temperature and approval (gas: approved sealants only).

Finishes: black or galvanised?

Black (Fe): technical applications – gas, heating, compressed air, closed systems.
Hot-dip galvanised (Zn): to EN 10242; GF uses high-purity zinc → suitable for drinking water (DVGW-certified). The galvanised version is intended for cold-water/drinking-water installation; electro-galvanising, by contrast, is only a thin protective coating – an important distinction.

Working limits and approvals

The standard range to EN 10242 covers liquids and gases up to 25 bar working pressure; typical media per GF catalogue: drinking water up to 60 °C, system waters up to 130 °C, natural/town/liquefied gas, compressed air (oiled and oil-free). For higher pressures there are specially pressure-tested fittings (burst-pressure tested, 100 bar test pressure, yellow marking). The test pressure is not a permissible working pressure – working pressure, medium and temperature follow from the data sheet of the specific version. Approvals: DVGW/ÖVGW/SVGW certificates, FM-approved range for fire-protection/sprinkler systems, CPR/RoHS/PED conformity, inspection documents to EN 10204 available.

Common mistakes in practice

Mixing NPT, G and R/Rp threads.
Ordering by nominal size only instead of type no. + standard + finish + thread version.
Too much hemp or PTFE tape residues in the system; hemp with oxygen.
Black fittings in drinking-water installations.
Trying to weld malleable cast iron (changes the microstructure).
Confusing electro-galvanised with hot-dip galvanised.
Using standard fittings above 25 bar instead of the pressure-tested version (yellow marking).

Frequently asked questions

How does a pipe thread to EN 10226-1 seal?

A taper external thread R is screwed into a parallel internal thread Rp (or a taper internal thread Rc to Part 2) – the metallic sealing pressure is created in the thread itself. This is the standard for malleable iron fittings. Not to be confused with the G thread to EN ISO 228-1: parallel, not sealing in the thread – it seals with a washer on a shoulder face.

Do NPT fittings fit R threads?

No. NPT (North American) has its own taper angle and flank profile and is not compatible with R/Rp despite looking similar – it may screw in, but it will never seal permanently.

What matters when sealing with hemp?

Hemp with jointing paste is well proven on R/Rp metal threads; the sealant must comply with EN 751. Typical mistakes are using too much hemp and contamination; hemp is unsuitable for oxygen service.

What matters when using PTFE tape?

Winding direction and quantity are decisive: with a standard right-hand thread, wind the tape in the screwing-in direction so it does not unwind during assembly. The number of layers and the thread turns to leave free follow the manufacturer's instructions. Typical mistakes: tape residues in the system and the wrong winding direction. For gas, only approved sealants may be used.

When are anaerobic thread sealants suitable?

Anaerobic sealants cure between metal faces in the absence of air. Their limits are inactive materials (e.g. stainless steel without an activator) and large gaps. Selection always depends on medium, temperature and approval.

What is the difference between DIN 2950 and EN 10242?

EN 10242 is the product standard for malleable iron fittings and has replaced the national standards – in Germany DIN 2950. If you have old parts lists or existing installations with DIN 2950 designations, EN 10242 provides the successor system.

What does EN-GJMW-400-5 mean?

Whiteheart malleable cast iron to EN 1562 with 400 N/mm² tensile strength and 5 % elongation at fracture – the material GF uses for its malleable iron fittings.

Are galvanised malleable iron fittings suitable for drinking water?

GF fittings are hot-dip galvanised to EN 10242; GF uses high-purity zinc, which makes them suitable for drinking water (DVGW-certified). The galvanised version is intended for cold-water/drinking-water installation; electro-galvanising, by contrast, is only a thin protective coating.

Can malleable cast iron be welded?

Malleable cast iron is not a welding material like steel – higher temperatures change the microstructure. Connections are made by thread, not by weld.

What does the yellow marking on GF fittings mean?

The yellow marking identifies specially pressure-tested fittings for pressures above the 25 bar of the standard range – burst-pressure tested, 100 bar test pressure. The test pressure is not a permissible working pressure; the data sheet of the specific version governs.

Frequently asked questions

Which number belongs to which malleable iron fitting?

Choose the fitting number in the chart at the top – elbow 90, tee 130, socket 270 and the rest to EN 10242 with name and symbol; the range board shows the shapes in a picture. Dimensions, sketch and availability per number and size are in the dimension table by number; material, R and Rp threads, finishes and limits of use in the basics below.

Joining or repairing without welding? Compression fittings, repair clamps and tapping clamps join, seal and branch – without welding and without press tools. The tool shows which solution fits the pipe, outside diameter and medium. Which solution fits?

GF malleable iron fittings – available from stock

One of the largest GF malleable iron stock ranges in the German-speaking region – threaded fittings to EN 10242, black or galvanised, delivered across Europe. Ask us for prices, availability and EN 10204 certificates.

Send us your inquiry

Your inquiry to Zickwolff

Send us what you have – designation, standard, quantity, date. We will clarify the rest with you.

One item or a question

Send inquiry

Not in stock? We procure it – single items too.

Designation, standard and quantity are enough.

Several items

Send bill of materials

200 items? One parts list is enough – we deliver complete.

Attach it as a file.

Helpful if already known: project and country, date needed, certificates, packaging and language of the packing lists. If anything is missing, we will ask.

It is urgent

Request express

When do you need it? Express delivery, to the site if required.

Tell us by when you need the material – we will tell you what is possible.

← Back to the English knowledge hub

Technical basis: EN 10242 (formerly DIN 2950), EN 1562, EN 10226-1/-2, EN ISO 228-1, EN 751 and technical documentation from Georg Fischer (GF). All information without guarantee – the current standard texts and the manufacturer's technical data sheets always prevail.