The answer to 'how do I know if I need to replace my water heater' is that there are several signs that indicate it may be time to replace your water heater. If your water heater is over 10 years old, it's generally recommended to start considering replacement, as the average lifespan is 8-12 years. Other signs include leaks, rust, lack of hot water, or strange noises coming from the unit.
It's important to pay attention to the age and performance of your water heater, as a failing unit can lead to expensive water damage and other issues. If you notice any of these warning signs, it's best to have a professional plumber inspect the unit and provide recommendations on whether a replacement is needed.