You'll primarily need good lighting, such as a flashlight or headlamp, to clearly see the serial number and inspect for small leaks or corrosion in dark areas. A camera on your phone can also be helpful for documenting findings or reaching tight spots to photograph the serial number. Keep a rag handy to wipe away dust or condensation for a clearer view.

Always be cautious around hot water pipes and the unit itself, which can be very hot. For gas water heaters, be aware of any gas smell, and never attempt to inspect if you suspect a gas leak. For electric units, you may want to turn off the power at the breaker if you need to touch electrical components, though for visual inspection, this isn't usually necessary.

Yes, even without visible leaks, an older water heater becomes less efficient, increasing your energy bills. There's also a higher risk of sudden, catastrophic failure, which could lead to significant water damage. Proactive replacement can save you money in the long run and prevent unexpected emergencies.

The ability to repair depends on the leak's source. Minor leaks from fittings, valves (like the T&P relief valve), or drain spigots can often be repaired or replaced relatively easily. However, if the leak is coming directly from the tank itself, especially from the bottom or sides, it usually indicates internal corrosion and almost always requires a full water heater replacement.