What is one key maintenance task for hot water systems?

Flushing sediment from the tank is an essential maintenance task for hot water systems because it helps to remove buildup that naturally occurs over time. Sediment, often made up of minerals like calcium and magnesium, can settle at the bottom of the tank and lead to reduced efficiency, potential overheating, and ultimately, malfunctioning of the system. By performing this maintenance regularly, homeowners can ensure that their hot water systems operate efficiently, leading to longer lifespan and more reliable access to hot water.

The other options, while also important in various contexts, do not address the critical issue of sediment buildup directly. Changing the water filter is necessary in systems that have filtration but may not apply to all hot water systems. Replacing the thermostat is relevant when heating issues arise, but it does not touch upon the everyday maintenance required for efficiency and performance. Cleaning the exterior surfaces is good practice for aesthetics and minor maintenance but does not impact the core functionality of the hot water system as directly as sediment flushing does.