Naturally occurring minerals (primarily iron and manganese) flowing with the water are typically to blame for water discoloration. These minerals, which are heavier than water, settle in water pipelines when water usage is low — especially during winter months. When the water flow and pressure through the water pipes increases again (due to irrigation, construction, etc.) the minerals are stirred up and flow out of your faucets when you turn on the tap. Water utilities frequently attempt to minimize water discoloration by “flushing out” their systems on a regular basis.