Class K8 DN250 ductile iron pipe has a nominal wall thickness of 6.0 mm per ISO 2531 (K = 8) , offers PN 12.5 (1.25 MPa) working pressure, and delivers a 100 + year service life with cement‑mortar lining and polyethylene sleeving. It installs rapidly via push‑on (“Tyton”), mechanical or flanged joints compliant with ISO 2531, AWWA C111 and EN 1092. Compared with adjacent thickness classes (K7→6.0 mm, K9→6.8 mm, K12→9.0 mm), K8 balances cost (≈ $500–600 USD/ton) and performance.
Applications
Potable Water Distribution
Class K8 DN250 pipe ensures leak‑tight delivery in municipal networks, resisting internal pressure fluctuations and maintaining water quality .
Sewage & Drainage
Its abrasion‑resistant iron core and robust lining handle grit‑laden wastewater under gravity or forced mains .
Irrigation Systems
Uniform hydraulic performance and surge resistance support agricultural supply lines and farm sprinklers.
Gas Distribution
When produced per EN 969 and coated externally, DN250 K8 pipe safely conveys natural gas in medium‑pressure networks.
Fire‑Protection Mains
High ductility and surge tolerance make it ideal for fire‑water loops and hydrant feeder mains.
Service Life
Uncoated ductile iron in benign soils lasts > 100 years, with cement‑mortar linings and polyethylene sleeving extending that to 110 years under optimal conditions . A Black & Veatch study estimated a $17 million present‑value savings over 50 years (3 % annual O&M reduction) when using DIP vs. PVC.
Installation & Connection
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Push‑On (“Tyton”) Joints: Spigot‑socket with elastomeric gasket enables rapid, bolt‑free assembly per ISO 2531 socket dimensions.
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Mechanical Joints: Gland‑and‑bolt restraint per AWWA C111 for fittings and valve connections, offering axial restraint where needed.
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Flanged Joints: ANSI B16.1 or EN 1092 flanges allow disassembly for maintenance and resist axial loads.
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Best Practices: Trenches require 150 mm well‑graded bedding, deflection limits ≤ 3 % of DN, hydrostatic testing and disinfection per ISO 2531/AWWA C600 guidelines.
K‑Series Comparison & Pricing
| Class | Wall Thickness (mm) | Pressure Rating | Price (USD/ton) |
|---|---|---|---|
| K7 | e = 7×(0.5 + 0.001 × 250) = 6.0 | PN10 (1.0 MPa) | $480 – 530 |
| K8 | e = 8×(0.5 + 0.001 × 250) = 6.0 | PN12.5 (1.25 MPa) | $500 – 600 |
| K9 | e = 9×(0.5 + 0.001 × 250) = 6.8 | PN16 (1.6 MPa) | $545 – 645 |
| K12 | e = 12×(0.5 + 0.001 × 250) = 9.0 | PN25 (2.5 MPa) | $750 – 900 |
Wall‑thickness formula: e=K (0.5 + 0.001 × DN).
International Standards
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ISO 2531:2009 / EN 545:2006 – Pipe dimensions, linings, joint performance .
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GB/T 13295‑2019 – Chinese specification for DIP, fittings & joints in water/gas systems .
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ISO 8180:2020 – Polyethylene encasement for external corrosion control .
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ANSI/AWWA C111/A21.11 – Mechanical joint specifications.
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EN 969 – Gas‑pipeline ductile iron pipe, fittings & accessories requirements.
Advantages
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Exceptional Longevity: 100 + year service life reduces replacements .
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High Strength & Toughness: Tensile ≥ 420 MPa resists surge and external loads .
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Superior Corrosion Control: Internal cement‑mortar, zinc/bitumen coatings, LPS.
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Versatile Joint Options: Push‑on, mechanical, flanged, restrained systems for site‑specific needs.
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Sustainable: Fully recyclable with lower life‑cycle energy use vs. thermoplastics .
FAQ
Q1: How do K classes differ?
They follow e=K (0.5+0.001 DN): for DN250, K7/K8=6.0 mm, K9=6.8 mm, K12=9.0 mm, matching PN 10/12.5/16/25 respectively.
Q2: What lining & coating options exist?
Cement‑mortar, epoxy or ceramic internal linings; external bitumen, zinc or polyethylene sleeving per ISO 8180.
Q3: Is DIP suitable for corrosive soils?
Yes—with loose polyethylene encasement or cathodic protection, DIP achieves 100 + year life in aggressive environments.
Q4: What sizes & lengths are offered?
Standard DN 80–2600 mm in 6 m (5.7 m for containers) laying lengths, custom cuts on demand .
Q5: Can DIP be used in seismic areas?
Yes—restrained joints (tie‑rod, ball‑and‑socket) absorb ground movement for seismic resilience.
Case Studies
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Huntsville Utilities, AL: Black & Veatch found $17 million PV savings over 50 years (3 % annual O&M reduction) vs. PVC mains.
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Everglades City, FL: DIP with polyethylene encasement remained in “excellent condition” after 10+ years in corrosive muck (140–240 Ω‑cm).
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 | ….. |
