Class K9 DN700 ductile iron pipe excels in municipal and industrial water, sewage, and fire-fighting networks thanks to its high pressure rating (PN 25), excellent corrosion protection, and long service life exceeding 100 years in favorable soils. Installation options include flexible push-on joints, restrained K-type, and standardized flanged ends for rapid, leak-free assembly. Compared to K7, K8, and K12 classes, K9 balances wall thickness (≈ 10.8 mm) with durability, while price tiers range from USD 450–550 /m for small lots to USD 650 – 850 /m for bulk orders. Fully compliant with ISO 2531, EN 545, EN 598, ISO 4179, and ISO 8179, it offers high tensile strength (> 420 MPa) and recyclability, making it a sustainable choice.
Application Scenarios
Class K9 DN700 ductile iron pipe is widely used in municipal potable water and raw water networks, delivering large flow volumes with minimal head loss for urban distribution systems. It also serves sewage, stormwater, and industrial effluent mains where mechanical robustness and leak resistance are critical.
In fire-fighting mains and hydrant systems, its PN 25 rating and inherent ductility ensure reliable operation under surge pressures up to 40 bar when combined with restrained joints. The DN700 size particularly suits large-scale irrigation and hydroelectric conduits, sustaining consistent pressure over long distances.
Service Life
Ductile iron’s metallurgical improvements provide a design life of 100 years in benign soils, with field installations often surpassing this under proper maintenance. Even in aggressive soils, corrosion protection systems (zinc + bitumen coatings, cement mortar linings, fusion-bonded epoxy) extend service life to 50–80 years.
Life-cycle assessments confirm that recyclability and low maintenance requirements yield one of the lowest total costs of ownership among pipe materials.
Installation & Connections
Push-On (Tyton) Joints
Flexible, gasketed push-on joints permit angular deflection up to 5°, simplifying alignment in trenchless and curved installations with 100% leak-free performance when properly assembled.
Restrained (K-Type) Joints
K-type restraining devices lock socket and spigot against axial thrust, providing zero-leak performance under surge and vacuum conditions and enabling pre-backfill pressure testing.
Flanged Connections
Flanged ends per EN 1092-2 support PN 25 service and integrate seamlessly with valves and pumps. Flanged surfaces undergo pure zinc (200 g/m²) + bitumen protection for enhanced durability.
Series Comparison & Price
| Class | Wall Thickness (mm) | Nominal Pressure (PN) | Approx. Weight (kg/m) | Price Range (USD/m) |
|---|---|---|---|---|
| K7 | 7.7 | PN 10 | 63.2 | 450 – 550 |
| K8 | 8.6 | PN 16 | 89.7 | 500 – 650 |
| K9 | 10.8 | PN 25 | 173.9 | 650 – 850 |
| K12 | 15.3 | PN 40 | 420.1 | 800 – 1 000 |
Choosing among K-classes balances cost versus pressure capacity and impact resistance, with K9 ideal for DN700 in demanding applications.
International Standards
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ISO 2531: Dimensions, materials, and testing for water applications.
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EN 545 / EN 598: European standards for drinking water and sewage pipes.
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ISO 4179: Internal cement mortar lining requirements.
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ISO 8179: External zinc + bitumen coating specifications.
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ISO 21053: Life-cycle and sustainability assessment.
Advantages
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High Tensile Strength (> 420 MPa) and Ductility accommodate ground movement without fracture.
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Long Service Life (50–100 years) with minimal maintenance.
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Excellent Corrosion Resistance via multi-layer coatings and linings.
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Fast, Leak-Free Installation with standardized joints.
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Environmentally Sustainable: high recycled content, fully recyclable.
FAQ
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What is Class K9?
A thickness class (~ 10.8 mm for DN700) rated PN 25 per ISO 2531. -
How long does DN700 K9 last?
100 years in benign soils; 50–80 years with standard protection in aggressive soils. -
Which joint suits high-rise or surge-prone systems?
Restrained K-type joints ensure axial restraint and leak-proof service under varying pressures. -
What linings and coatings are standard?
Cement mortar lining (ISO 4179), internal epoxy, plus zinc (200 g/m²) + bitumen (ISO 8179) externally. -
Is DN700 K9 suitable for potable water?
Yes—EN 545 compliance, cement-mortar lined, zinc-coated, PN 25 flanged connections.
Case Studies
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Urban Renewal Water Project (City A): Replaced aging mains with 700 mm K9 pipe, achieving optimal pressure, 30% reduction in maintenance calls, and lifecycle cost savings ~ 20%.
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Riyadh Sewer Line Project, Saudi Arabia: 12 km of DN700 K9 sewers lined with Portland cement, commissioned 2014, maintained structural integrity in sulphate-rich soils with zero failures over 8 years.
ductile iron pipe dimensions
| Pipe body weight （kg/m) | |||||||||||||||
| (Inside Diameter) | (Outside Diameter) | Socket Weight | K8 | K9 | K10 | C class | Total weight of Active Length=6M (kg) | Total weight of Active Length=5.7M (kg) | |||||||
| DN(mm) | OD(mm) | ≈ kg | Class | kg/m | K8 | K9 | K10 | C class | K8 | K9 | K10 | C class | |||
| 80 | 98 | 3.40 | 12.20 | 12.20 | 12.20 | C40 | 9.10 | 77.00 | 77.00 | 77.00 | 58.00 | 73.00 | 73.00 | 73.00 | 55.00 |
| 100 | 118 | 4.30 | 14.90 | 15.10 | 15.10 | C40 | 11.12 | 93.70 | 95.00 | 95.00 | 71.00 | 90.00 | 91.00 | 90.00 | 68.00 |
| 125 | 144 | 5.70 | 18.90 | C40 | 119.00 | ||||||||||
| 150 | 170 | 7.10 | 21.80 | 22.80 | 22.80 | C40 | 16.48 | 138.00 | 144.00 | 144.00 | 106.00 | 132.00 | 138.00 | 137.00 | 101.00 |
| 200 | 222 | 10.30 | 28.70 | 30.60 | 30.60 | C40 | 22.62 | 183.00 | 194.00 | 194.00 | 146.00 | 174.00 | 185.00 | 185.00 | 139.00 |
| 250 | 274 | 14.20 | 35.60 | 40.20 | 44.30 | C40 | 32.63 | 228.00 | 255.00 | 280.00 | 210.00 | 218.00 | 244.00 | 267.00 | 200.00 |
| 300 | 326 | 18.90 | 45.30 | 50.80 | 56.30 | C30 | 43.90 | 290.00 | 323.00 | 357.00 | 282.00 | 278.00 | 309.00 | 340.00 | 269.00 |
| 350 | 378 | 23.70 | 55.90 | 63.20 | 69.60 | C30 | 51.88 | 359.00 | 403.00 | 441.00 | 335.00 | 343.00 | 384.00 | 420.00 | 319.00 |
| 400 | 429 | 29.50 | 67.30 | 75.50 | 83.70 | C30 | 60.78 | 433.00 | 482.00 | 532.00 | 394.00 | 414.00 | 460.00 | 506.00 | 376.00 |
| 450 | 480 | 38.30 | 80.00 | 89.30 | 99.00 | C30 | 73.30 | 515.00 | 575.00 | 632.00 | 472.00 | 492.00 | 550.00 | 597.00 | 450.00 |
| 500 | 532 | 42.80 | 92.80 | 104.30 | 115.60 | C30 | 87.20 | 600.00 | 669.00 | 736.00 | 566.00 | 572.00 | 638.00 | 702.00 | 540.00 |
| 600 | 635 | 59.30 | 122.00 | 137.30 | 152.00 | C30 | 120.62 | 791.00 | 882.00 | 971.00 | 783.00 | 755.00 | 842.00 | 926.00 | 747.00 |
| 700 | 738 | 79.10 | 155.00 | 173.90 | 193.00 | C25 | 142.15 | 1009.00 | 1123.00 | 1237.00 | 932.00 | 963.00 | 1071.00 | 1179.00 | 889.00 |
| 800 | 842 | 102.60 | 192.00 | 215.20 | 239.00 | C25 | 177.07 | 1255.00 | 1394.00 | 1537.00 | 1165.00 | 1197.00 | 1330.00 | 1465.00 | 1112.00 |
| 900 | 945 | 129.60 | 232.00 | 260.20 | 289.00 | C25 | 197.68 | 1521.00 | 1691.00 | 1863.00 | 1446.00 | 1452.00 | 1613.00 | 1777.00 | 1257.00 |
| 1000 | 1048 | 161.30 | 275.00 | 309.30 | 343.20 | C25 | 266.28 | 1811.00 | 2017.00 | 2221.00 | 1759.00 | 1729.00 | 1925.00 | 2118.00 | 1679.00 |
| 1100 | 1152 | 194.70 | 362.80 | 2372.00 | |||||||||||
| 1200 | 1255 | 237.70 | 374.00 | 420.10 | 466.10 | C25 | 373.88 | 2482.00 | 2758.00 | 3034.00 | 2481.00 | 2370.00 | 2632.00 | 2894.00 | 2369.00 |
| 1400 | 1462 | 279.30 | 547.20 | 3563.00 | |||||||||||
ductile iron pipe Mechanical property
| Mechanical Property | |||||||
| Nominal Diameter | Hydraulic test | Tensile strength | Elogation | Yield strength | Bending strength | Brinell hardness | Thickness of cement lining |
| DN(MM) | Mpa | Mpa | % | Mpa | Mpa | HB | mm |
| DN80-DN300 | 5 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 3 |
| DN350-DN600 | 4 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 5 |
| DN700-DN1000 | 3.2 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 6 |
| DN1100-DN1600 | 2.5 | ≥420 | ≥7 | ≥300 | ≥590 | ≤230 | ….. |
