I don't think it an issue unless it is leaking, however when the plumber is there get him to inspect the heater and make sure the heater itself isn't leaking. Obviously if the heater is leaking then yes replace it. Also avoid mr. Rooter, they charge a lot and usually there guys aren't all that qualified. Just do a bit of research and see who does good work in your area. Some of those companies who charge flat rates to do the work tend to be expensive, I used to work for one and our prices were outrageous.