Ductile iron pipes · Size & tolerance table

Ductile iron pipe outside diameters and K9 wall thickness (ISO 2531 / EN 545)

Standard: ISO 2531 · EN 545 (water) · EN 598 (sewerage)

Ductile iron pipes are made to a fixed outside diameter per DN, the same in ISO 2531, EN 545 and EN 598, so pipes and fittings from different makers fit the same joints. Wall thickness is set either by a thickness class (K7, K9, K10…) or, in EN 545 since 2010 and ISO 2531, by a pressure class (C25, C30, C40…).

For a K class the nominal iron wall is K × (0.5 + 0.001 DN) mm, with a minimum of 6 mm for K9. K9 is still the class most specified for water mains in the GCC and South Asia.

Outside diameter and K9 wall

DN	OD mm	e (K9) mm	Bore mm
80	98	6.0	86
100	118	6.0	106
125	144	6.0	132
150	170	6.0	158
200	222	6.3	209
250	274	6.8	261
300	326	7.2	312
350	378	7.7	363
400	429	8.1	413
450	480	8.5	463
500	532	9.0	514
600	635	9.9	615
700	738	10.8	716
800	842	11.7	819
900	945	12.6	920
1000	1048	13.5	1021
1100	1152	14.4	1123
1200	1255	15.3	1224
1400	1462	17.1	1428
1500	1565	18.0	1529
1600	1668	18.9	1630
1800	1875	20.7	1834
2000	2082	22.5	2037

Notes

The internal cement-mortar lining (ISO 4179: about 3 mm up to DN 300, thicker on larger sizes) reduces the bore further.
Minimum wall thickness is less than nominal by a tolerance of (1.3 + 0.001 DN) mm.
Push-on (socket and spigot) pipes are usually supplied in 6 m lengths; some makers use 5.5 m, and large diameters can be longer.