If you have copper pipes the colored stain is a dissolved form of copper being deposited on lighter colored surfaces. It is usually caused by corrosive waters that have low pH (acidic) and often have a low mineral content. Water is called the ‘universal solvent’ for a good reason. Water that has a low mineral content and is only slightly acidic will dissolve anything it can. If left unchecked the corrosive water will eat through your copper pipes.
One method of treatment is to ‘lime’ the water. This increases the pH and adds calcium minerals that will tend to deposit on the pipes instead of allowing the water to corrode the pipes. To find out if your water is acidic or alkaline, just send us a sample.