Back in December I got the elements changed in my Megaflow tank. A few months later the fuse started tripping every so often. One time when I flipped it the plug for the tank gave a good sizzle. I had a sparkie friend have a look and he replaced the plug for me. All was fine until last week when I stopped getting any hot water. The boost still worked but I called the plumber back in and he replaced the thermostat once again at the start of the week but I'm still not getting any hot water. What else could be wrong with the damn thing?