Contact corrosion occurs when two metals with different levels of nobility come into contact. In drinking water installations, this is referred to as the flow rule. The definition of the flow rule can be found in DIN EN 806-4. This standard is a recognized rule of technology for drinking water installations in domestic use. The flow rule states that galvanized steel pipework must be installed upstream of copper pipework in the direction of water flow. In other words, in the direction of flow, galvanized steel must come first, followed by copper pipe.
