2.6 Fuel con***ination
2.6.1. Materials and/or their surface treatment used for the storage and distribution of fuel are to be selected such that they do not introduce con***ination or modify the properties of the fuel. The use of copper or zinc compounds in fuel piping systems where they may come into contact with the fuel is not permitted. Copper-nickel materials are permissible but are to be limited to positi*** after the filtration/water absorption equipment required by 2.4.2.