To avoid confusion over debits and credits, avoid thinking of them in the way that they are used in everyday language, which often refers to a credit as increasing an account and a debit as decreasing an account. For example, if our bank credits our checking account, money is added to it and the balance increases.
One way to reduce the frequency of this occurrence is to maintain an air pocket at the top of the water heater tank. This air pocket will form in the tank by design - however, it will be reduced over time by the everyday use of your water heater. To replenish this air pocket: Turn off the water heater.
With the unit off or unplugged, attach a water hose to the hose bib at the bottom of the water heater. The hose bib is for draining the water heater. Let the cold water fill the water heater as you flush out any sediments or mineral build up. Scheduling a water heater flush once a year can result in extending the life of your water heater. Annually check the pressure relief valve to ensure it is working. Wear thick gloves before lifting up on the test release lever atop the water heater. If it is working properly, hot water escapes via the overflow pipe.