Fitted an immersion heater for a friend about a year ago, replacing one which had failed. It is a 3KW, 11 inch one which goes in across the bottom of the tank. It is on economy 7. There is also another heater near the top of the tank for topping up the hot water. Anyway, friend called last week to say that the overnight hot water was not working, so I popped round to see. Fuse had gone, so I checked the element - open circuit. So I had to drain the complete tank to remove it. I have never seen the like before, the whole of the tube containing the element had split along its length, and I mean the whole length. I did buy the original from Wickes. Needless to say they don't want to know. What is the average life of an immersion heater? We are not in a particularly hard water area, the top heater has been there for years, with no problem, and the old one I took out had no physical damage either.