The Treasure Valleys potable water is supplied by ground water wells which are naturally rich with minerals; primarily calcium, magnesium, iron and manganese. These minerals are naturally occurring in our water and are harmless, however, when they come in contact with chlorine (the disinfectant we use in our water system), they oxidize (iron turns red, manganese turns black), become heavier, and settle in our water lines. During demands/flows in our water lines this sediment can be stirred up and make its way into a home’s water system.
Manganese, when it turns black, will look like “oil” and will stick to the sides of tubs and other plumbing fixtures. You can smear the marks with your finger which is an indication that it is indeed manganese. You can easily clean off the fixture using a magic eraser or other cleaning methods. If you encounter red/pink water for a short time your lines will need to be flushed.
When you encounter discolored water, you should flush your cold-water lines until clear. This could take a few minutes or so. You don’t want to flush your hot water side as it will pull the sediment into your water heater. If discoloring is coming from the hot water side you may need to flush your water heater. That is done usually by putting a hose on the discharge valve and flushing outside till clear.
If the problem persists please contact your local water department to investigate further.