There is a threshold for requiring barrier pipes, its when the use of PE or PVC pipes is prohibited because of the concentrations of hydrocarbons present exceeding the thresholds for using these materials - you then progress along the line of materials to choose.
As an example if your VOC concentration is <0.125mg/kg you could use PVC, if the concentration was up to 0.5mg/kg you could use PE and if the concentration of VOC was greater than 0.5mg/kg you could use barrier pipe, wrapped steel, wrapped ductile iron or copper.
Regards
Clive Williams
Halcrow
A CH2M Hill Company
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