When a water heater reaches a certain age, it can be easy to assume it’s living on borrowed time. It’s hard to say how long your water heater will last. Certified home inspectors estimate the life span to be about 10 years. Some manufacturers suggest 12 to 13 years, but it’s not unheard of for a water tank to last more than 40 years before the heating element finally gives out. That said, it’s wise to replace a water heater before it fails, because that failure can cause a lot of damage.