Water heater tanks generally require annual maintenance, and in some regions, they need to be serviced every six months. Alternatively, tankless water heaters require very little upkeep. Depending on the quality of your water supply, they can sustain full function for four to five years without maintenance.
If you live in an area with hard water, an annual cleaning is still recommended to remove mineral buildup near the heating element. This standard maintenance is easy to perform: use a vinegar solution to flush the unit for 60 minutes and remove any lingering sediment.