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Malleable iron fittings are a type of durable threaded pipe connector designed for the high-pressure transportation of water, gas, oil, steam and air and are used used in a wide variety of applications from plumbing to fire suppression systems.
According to the BMTFA (British Metals Tubes and Fittings Association) malleable iron fittings are available in both whiteheart and blackheart forms, and both perform satisfactorily in service. However, the association notes each material type can be manufactured in a range of different material grades, meaning not all fittings have the same technical performance characteristics.
The distinction between the two lies in the manufacturing process. Whiteheart malleable iron is produced using a longer, higher-temperature annealing process that decarburises the outer layer of the casting. If the fitting is cut in half, the core appears silvery white, giving the material its name. This process improves ductility and machinability while producing a smoother external surface perfect for galvanising.
Blackheart malleable iron, by comparison, has a grey core and also offers good ductility. However, its rougher surface makes achieving a high-quality galvanised finish more challenging.
GF is almost exclusively the only supplier of whiteheart malleable iron fittings in the UK, manufacturing its fittings under the updated BS EN 10242:2025 ‘Threaded pipe fittings in malleable cast iron’ standard, at its production facility in Traisen, Austria. The manufacturing process is designed to deliver consistently high-quality fittings while supporting sustainable production practices.
Quality assurance is embedded throughout production, with up to 12 quality inspections, including a final pressure test for every fitting. Should a product fail any stage of inspection, the affected production batch is rejected, ensuring only compliant products leave the factory.
Since 1864, more than 11 billion GF malleable iron fittings have been installed worldwide, providing a proven record of reliability and performance.
What are the benefits of GF’s enhanced thread design for malleable iron fittings?
GF malleable iron fittings incorporate an advanced thread design, improving joint integrity, corrosion resistance and long-term reliability. Unlike conventional fittings that may contain “wash-out” threads, GF fittings feature fully cut precision threads, reducing the amount of exposed, uncoated metal in galvanised fittings. This helps improve corrosion protection and reduces the potential for water to reach vulnerable areas of the fitting.
The fittings have an increased wall thickness around the threaded section, providing additional strength where the highest mechanical stresses occur, enabling the fitting to withstand higher assembly loads.
Each fitting is machine chamfered at the leading edge of the thread. This guides thread sealing materials into the joint during assembly, helping to produce a more effective seal, reducing the likelihood of leaks.
The extended annealing process also means the fittings require less torque to make the watertight connection and can withstand up to 30% higher assembly forces. GF’s fittings achieve accurate clocking alignment, allowing adjacent fittings to align consistently when fully tightened, providing improved installation accuracy and a neater finished pipework system.
Sustainability is at the heart of GF’s manufacturing process of malleable iron fittings. The fittings comprise of 96% iron with the remainder consisting of carbon and a small amount of other trace metals and elements. 100% of this iron comes from recycled sources. For example, old railway tracks that once carried millions of people are now trusted to carry services through miles of pipework.
What range of malleable iron fittings does GF have available?
GF offers the most comprehensive range of malleable iron fittings available, with more than 1,700 individual fittings, giving consultants and contractors extensive design freedom across plumbing, heating, cooling, industrial and fire protection systems.
The portfolio includes three product categories.
- Standard malleable iron fittings – Available in both black and galvanised finishes. Approximately 60% of the overall range is supplied galvanised, providing enhanced corrosion protection for applications where increased durability is required.
- High-pressure fittings – For applications requiring greater pressure resistance. Available in black and galvanised versions.
- Fire protection fittings – Specifically developed to meet fire suppression and sprinkler system installation requirements.
The breadth of the GF range enables complete pipework systems to be specified from a single manufacturer, simplifying procurement, ensuring product compatibility and providing greater flexibility.
GF offers comprehensive support throughout the project lifecycle, with BIM files, Environmental Product Declarations (EPDs) and experienced project teams to help ensure specifications meet the latest standards and project requirements. If you would like to find out more about our range of GF malleable cast iron fittings, please contact us today.
