A water heater should be flushed out and refilled annually.  Left alone, this sediment will impact the water heater’s ability to heat water, making it less efficient, and can also corrode the inside of the tank leading to premature failure.  All water heaters need to be drained & flushed every 12 months to maintain your manufacturer’s warranty.  Without annual maintenance your water heater sediment build-up will…reduce the amount of usable hot water, reduce your water heater’s efficiency (high utilities!) and reduce the overall lifespan of your water heater.