In building water supply and drainage, and in municipal engineering, cast iron pipes are highly favored for their durability, corrosion resistance, and noise reduction. However, when faced with the two European standards, EN545 and EN877, many engineers, procurement personnel, and designers may be confused: They both appear to be “iron pipes,” so what exactly is the difference?
In fact, there are fundamental differences between the two, and the choice between them directly impacts the safety, reliability, and economic efficiency of a project. Simply put, EN545 is the “strong” standard for pressure water pipes, while EN877 is the “specialist” for non-pressure drainage pipes. Understanding their differences is the first step in making the right material selection.
- EN877 cast iron pipe (gray cast iron): This is a traditional cast iron. Its carbon content exists in the form of flake graphite. These graphite flakes act like countless “natural cracks” embedded in the metal matrix, severely disrupting the matrix’s continuity. When subjected to tension or impact loads, stress is concentrated at the tips of these graphite flakes, making the material highly susceptible to brittle fracture. Consequently, EN877 cast iron pipe is known for its high hardness and acceptable compressive strength, but also for its extremely poor toughness and brittleness.
- EN545 ductile iron pipe: This is a result of modern metallurgical technology. During the smelting process, nodularizing agents (such as magnesium and rare earth elements) are added to the molten iron to transform the graphite from flakes to spherical shapes. This transformation is revolutionary: the spherical graphite minimizes the disruptive effect on the metal matrix, eliminating severe stress concentration points. This allows the metal matrix to fully realize its strength and ductility. Ductile iron thus combines the strength of steel (high tensile strength) with the excellent properties of cast iron.
| Ductile Iron Pipe | SML pipe | |
| Mechanical Properties | High strength, high toughness, impact resistance | High brittleness and poor impact resistance |
| Tensile Strength | ≥ 420 MPa | ≈ 150 MPa |
| Interface Form | Flexible interface (such as T-type, K-type mechanical interface) | Rigid joints (such as socket-type cement-hemp joints or simple rubber ring joints) |
| Main Application | Municipal water supply network, high-pressure sewage pipe, industrial water pipe, fire protection pipe network | Internal drainage/rainwater systems in buildings, and non-pressure municipal drainage pipes |
How to choose right ductile cast iron pipe?
When your system involves conveying pressurized fluids and places extremely high demands on pipe safety and reliability, EN545 ductile iron pipe is the preferred choice.
- Municipal water mains: These pipes bear the weight of the city’s “blood vessels,” bearing the brunt of internal water pressure and external soil loads.
- High-pressure sewage and industrial pipes: These are used for pressure-discharge pipes after pumping stations and for conveying media in industrial applications.
- In areas requiring earthquake resistance: Their flexible joints effectively offset displacement caused by seismic waves, preventing pipe system collapse.
- In areas traversing complex foundations: They can accommodate a certain degree of uneven settlement.
When your system is a non-pressure, gravity-fed system with fireproofing and silent operation requirements, EN877 cast iron pipe is a cost-effective and practical choice.
- Indoor building drainage systems: These are the perfect solution for everything from bathrooms and kitchens to drainage risers.
- Roof drainage systems: These collect and discharge rainwater from within a building. Non-pressure municipal sewer pipe: Used for the collection and gravity-flow transport of domestic sewage and rainwater.
- For locations requiring high levels of sound insulation: The density and crystalline structure of cast iron pipes provide excellent sound insulation, far superior to plastic pipes.
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Post time: Oct-21-2025
