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.
A typical hot water heater connects to two pipes -- a cold water supply line and a hot water line. The pipes often have elbow joints so they can bend toward the water heater. Either of these water lines can leak, particularly at the joints. If water sprays from a fitting or pipe, the problem is clear. A dripping pipe or joint is less noticeable.