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.
Flush and Refill a Hot Water Heater. Turn off the gas valve or shut off the electricity breaker that powers the hot water heater. Connect a hose to the drainage valve located at the bottom of the hot water heater. Run the hose into a drain or outside; the water from the hot water heater will drain through it. Close the cold water valve.