What should be done first when draining a water heater?

Turning off the heat source is the appropriate first step when draining a water heater. This action ensures safety by preventing the heating element from becoming damaged while exposed to air and by avoiding potential burns or injuries.

When the heat source is turned off, the water temperature can begin to decrease, making the entire process safer. Additionally, this helps to avoid situations where the water heater could potentially overheat if its tank is drained while the heating element is still active.

Following this, opening the highest level faucets allows for air to enter the system, facilitating a smoother drainage process, and opening the pressure relief valve can help relieve pressure build-up. However, these actions should occur only after ensuring the heat source is off. Therefore, starting the draining process by turning off the heat source is a critical safety precaution.