said by ArgMeMatey: Unfortunately that is quite common by me. The water co is supposed to send a warning in advance but sometimes it "gets lost in the mail" and you are doing a white wash of laundry when brownish red water comes pouring out into the tub.
I helped a neighbor with a similar problem. Through a very unsophisticated process, I discovered that the water supply screen had gotten clogged with debris. The city had just flushed hydrants days before, so I am guessing that knocked this stuff loose - rust and slivers of wood.