Corrosion of carbon-based electrodes and bipolar plates is a major hurdle and can be a cause of failure in commercial vanadium redox flow batteries (VRFBs). Carbon corrosion was found to occur in a commercial VRFB (10 kW/40 kWh), whereby cracks through bipolar plates enabled the electrolyte to leach the copper current collectors at the end of the stacks, contaminating the entire electrolyte solution. In this work, the effects of copper contaminants on the operation of a VRFB were studied. A simple and effective procedure to identify copper contamination on-site and to purify the electrolyte was developed. The process was used to purify large quantities (6000 L) of copper-contaminated electrolytes to levels below 1 ppm.