What piping materials, black steel piping with cast iron/malleable iron fittings vs. galvanized pipe and fittings, have the lowest corrosion rate when used with softened water? Corrosion can occur with any type of piping depending on the application, environment and precautions taken to prevent corrosion. We at Res-Kem find that steel piping with iron fittings offers the best balance of corrosion resistance and cost. First, softened water has not shown to cause any more internal corrosion in steel or galvanized piping than hard water. Corrosion, which does occur with unlined steel tanks, piping & fittings or galvanized tanks pipe & fittings is generally caused by other factors. Some of these are pH, temperature, dissolved gasses (oxygen and carbon dioxide) in the water, contact with air and galvanic action.

While temperature itself is not generally a problem with water softening systems, high temperatures (>150º F) with low pH and/or dissolved oxygen/carbon dioxide can be extremely corrosive. This is particularly a problem with galvanized pipe and fittings. Any imperfection in the galvanizing will accelerate the corrosion, as it will attack the imperfections with zeal. Two of the biggest contributors to corrosion we typically see with industrial water treatment equipment (softeners, filters and dealkalizers) are galvanic action and contact with air.