To troubleshoot a leaking water heater, first, turn off the power or gas supply and shut off the water inlet valve. Identify the source of the leak, which could be from the temperature and pressure relief valve, the drain valve, or the tank itself. Tighten loose connections if applicable. If the leak persists, inspect the pressure relief valve for corrosion or debris buildup and replace if necessary. For leaks from the tank, consider contacting a professional plumber for repair or replacement to prevent water damage.