We have hard water here and have the hardness build up in the bottom of the tank to the point of the lower element being buried in the white hard chalky stuff within 3-4 years. I tried cleaning it out with the first one but ended up replacing it anyway. Now, if it's 3-4 years old, at the first sign of not enough hot water I just replace it myself. They're only about $250. Two pipes, one circuit, done in two hours, good for 3-4 more years.