The nominal wall thickness of Ductile Iron Pipe is calculated as a function of the nominal size (NB) utilizing the following formula:

e = K (0.5 + 0.001NB)
K = A coefficient used for the determination of Class thickness and is selected from a series of whole numbers normally from 7 to 14
e = The nominal wall thickness of the pipe
NB = The nominal bore of the pipe

The Ductile Iron Pipes are supplied in 6m lengths. The standard wall thickness and operating pressures are given below:

PFA – Allowable Operating Pressure
Internal pressure, excluding water hammers, that a component can safely and continuously withstand under hydraulic service.
PMA – Allowable Maximum Operating Pressure
Maximum internal pressure, including water hammer that a component can safely withstand during service.
PEA – Allowable Text Pressure
Maximum hydrostatic pressure that can be applied on site to a newly laid pipe component can withstand for a relatively short duration, when either fixed above ground level or laid and back-filled underground in order to measure the integrity and leak tightness of the pipe.



  • e1= The thickness of cement mortar lining
  • Pipes supplied in container loads will be in 5.5 or 5.7 metre length
  • A tolerance of +1mm applies
  • Thicknesses are greater for calculated for “smoothing” between C40 and C30 and also between C30 and C25