Ductile iron pipe wall thickness varies significantly based on nominal pipe size and design method—either by pressure class (per ANSI/AWWA C151/A21.51) or by thickness class (per ANSI/AWWA C150/A21.50). For pressure classes 150–350 psi, wall thickness ranges from 0.25 in for 3–6″ pipes up to 0.87 in for 64″ pipes. Alternatively, thickness classes (50–56) start at 0.25 in (class 51 for 3–4″) and increase in ~0.03–0.04 in increments per class. In Europe, ISO 2531/EN 545 defines metric nominal diameters (DN 40–DN 2000) with wall thicknesses in classes K9–K11, from 4.8 mm (K9) up to 7.5 mm (K11) for DN 40–250 mm. Selection depends on working pressure, surge allowance, trench load, cover depth, and application requirements to ensure structural integrity and long service life.
1. Design Standards
1.1 Pressure Classes (ANSI/AWWA C151/A21.51)
ANSI/AWWA C151/A21.51 specifies ductile iron pipe from 3″ to 64″ nominal size, classifying wall thickness by working pressure—150, 200, 250, 300, and 350 psi. Pressure classes correspond to rated water working pressure, with an additional 100 psi surge allowance in thickness design.
1.2 Thickness Classes (ANSI/AWWA C150/A21.50)
ANSI/AWWA C150/A21.50 defines “thickness classes” 50–56 independent of pressure, allowing special applications (e.g., threaded or grooved pipe) with nominal thicknesses from 0.25 in (class 51 for 3–4″) up to 1.05 in (class 56 for 54″) . Designers select the greater thickness required for internal pressure or trench loads, per AWWA C150 tables.
2. Wall Thickness by Pressure Class
| Nominal Size (in) | Outside Diameter (in) | Class 150 (in) | Class 200 (in) | Class 250 (in) | Class 300 (in) | Class 350 (in) |
|---|---|---|---|---|---|---|
| 4 | 4.80 | 0.26 | 0.26 | 0.26 | 0.26 | 0.26 |
| 6 | 6.90 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
| 8 | 9.05 | 0.27 | 0.27 | 0.27 | 0.27 | 0.27 |
| 12 | 13.20 | 0.31 | 0.31 | 0.31 | 0.31 | 0.31 |
| 16 | 17.40 | 0.34 | 0.34 | 0.34 | 0.34 | 0.34 |
| 24 | 25.80 | 0.38 | 0.38 | 0.38 | 0.41 | 0.44 |
Data from AWWA C151/A21.51 pressure-class tables.
3. Wall Thickness Classes
Based on ANSI/AWWA C150/A21.50 special “thickness classes” .
4. European Metric Standards (ISO 2531 / EN 545)
| DN (mm) | OD (mm) | Class 40 (mm) | Class K9 (mm) | Class K10 (mm) | Class K11 (mm) |
|---|---|---|---|---|---|
| 100 | 118 | 4.8 | 6.0 | 6.0 | |
| 150 | 170 | 5.0 | 6.0 | 6.5 | |
| 200 | 222 | 5.4 | 6.3 | 7.0 | |
| 250 | 274 | 5.8 | 6.8 | 7.5 |
Per ISO 2531/EN 545 metric classes for DN 40–DN 2000.
5. Selecting the Right Thickness
Key factors influencing wall thickness choice include:
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Working Pressure & Surge: Ensure nominal thickness covers rated pressure plus surge allowance (100 psi).
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Trench Load & Depth: AWWA C150 tables relate overburden and live loads to required thickness for burial depths.
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Joint Type & Accessories: Threaded, grooved, or special fittings may necessitate higher thickness classes.
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Corrosion Allowance: In aggressive soil or water conditions, extra thickness or linings may be specified.
6. FAQ
Q1: What determines ductile iron pipe wall thickness?
Wall thickness is set by either pressure class (150–350 psi) under AWWA C151 or by thickness class (50–56) under AWWA C150, selected based on working pressure, trench load, and application.
Q2: How thick is a 12″ Class 200 pipe?
A 12″ ductile iron pipe in pressure class 200 has a wall thickness of 0.31 in per AWWA C151 tables.
Q3: What is the surge allowance?
Surge allowance is an extra 100 psi factored into the wall thickness design to absorb transient pressure spikes.
Q4: How do European and American standards differ?
North America uses nominal inches and psi-based pressure classes or thickness classes, while Europe uses metric nominal diameters (DN) and classes K9–K12 per ISO 2531/EN 545 with fixed wall thicknesses in millimeters.
Q5: Can I use thickness class instead of pressure class?
Yes. Thickness classes under AWWA C150 allow specifying pipe thickness independent of pressure, useful for special applications requiring extra mechanical strength or corrosion allowance.
7.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 | |||||||||||
8.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 | ….. |