Pour some water into a white bowl and let it evaporate overnight. If you wake up to a rusty, powdery ring at the waterline, that’s iron residue. It’s like your water left a messy fingerprint on crime scene. Case closed, Sherlock.
Iron Level Water at Crystal Yazzie blog
And if you’re feeling especially silly, try the “toothbrush test.” Dip an old, dry toothbrush into the water, let it air-dry, and see if the bristles turn reddish. If yes, your water would make a terrible dentist but an excellent rust manufacturer.
