Is it worth it to repair a hot water heater?

Repair is usually worth it under about ten years old when the part is a stock item and the fault is a single component. Past twelve or thirteen years, with a scaled heat exchanger or parts that have to be hunted down, the repair money is a deposit on the next appliance. The three facts that decide it are the age, whether the part still exists, and whether the fault is one component or the body of the appliance.