It could be "poo" but more likely, it's rust, especially given that it's only found in water coming from certain taps. Ruhl, have you tried running the water until it's clear? This usually works if it is rust. However, there is some reason to be concerned that if there's rust, there could also be other contaminants, such as lead (from solder). I'd have a qualified plumber check it out. Also, there are home test kits you can buy to determine if your water is contaminated with lead, iron, e. coli, and a number of other goodies.
Jake