Most homeowners don’t realize that their storage-tank water heaters require annual maintenance every six to twelve months. In fact, some manufacturers will not honor the warranty if the water heater did not receive annual maintenance. With an on-demand heater, required maintenance is every five years unless you live in an area known for hard water. In the case of hard water, the recommendation is to remove any mineral deposits built up near the heating element. This basic maintenance is easily performed using a vinegar solution to flush the unit for sixty minutes, which removes any lingering sediment.