Hardness can contribute to mineral scale, but noises, leaks, reduced hot-water output, rusty water and high bills can have other causes. Treat symptoms as clues, not diagnoses.
They do not store a tank of water, but mineral scale can still form in heat exchangers and water passages. Maintenance should follow the specific manufacturer's instructions.
There is no universal 6-month or annual rule that fits every heater. Model design, water chemistry, usage and service history matter. Older or neglected tanks may require more caution, not more aggressive flushing.
A sediment filter targets suspended particles. A softener reduces hardness minerals such as calcium and magnesium. Choose treatment based on the actual water problem rather than assuming one device fixes everything.
Maintenance can help manage known service needs, but it cannot guarantee efficiency, savings or a specific lifespan. Heater construction, water chemistry, installation, usage and component condition all matter.
The maintenance-context tool can help organize known facts about the heater, but it does not measure sediment or prescribe a service interval.