Our house was built in 1940. We moved in two weeks ago and have been running a lot of water. However, there is a light rust color to the water when the bath tub is filled up and our single room humidifier has a rusty residue. Shouldn't the rust have washed away within a couple of days? Any recommendations to fix the problem? Is this a health hazzard?

Thank you very much in advance.

Was your house vacant or unoccupied for a long amount of time before you bought it?
Old houses usually have old galvanized pipes and get iron (and other mineral) build-up which makes the water rust colored.

While galvanized pipes can build up rust, my bet's on a water heater with built up minerals that hasn't been properly flushed and maintained. Betcha it's the hot water that has the color. Let'start with the water heater.
For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps, Tom