My mom has black residue(particulates,sludge)coming out of her taps and in her toilet bowls. It gets caught in the screens of the faucets, creates a layer of film on the inside of the toilet bowls, and is difficult to wash off. We're trying to figure out what this stuff is and where it came from, and what to do about it. The only other symptom to her plumbing problem is that every now and then there will be a rush of water that fills the toilet tanks without anyone flushing-as if there was a plug in the water supply line that was suddenly unblocked. Anyone have any ideas?