Was watching this old house this weekend. Homeowner had rust in bathtub water and was told it's time to replace the water heater. Is this really true? Our home is about 18 years with the original water heater. We rarely use the tub but whenever the water is turned on rust comes out. I never thought much about it and it's been doing it for years.I figured I'd keep the heater until it dies;can't see replacing it it because of some rust in the water. Some some earlier posts on this topic and have concluded it's no big deal.Wondered what someone else thought.