What could happen if the tank's internal surfaces become heavily scaled?

When the internal surfaces of a tank become heavily scaled, the buildup of scale can obstruct the flow of liquid within the tank. This obstruction can cause changes in pressure dynamics and create conditions where the tank may not fill properly, leading to an overflow situation. As the liquid continues to be pumped into the tank without the appropriate space for it to fill correctly, the excess liquid can spill over the top.

This scaling issue can also lead to uneven filling, where the liquid does not distribute uniformly throughout the tank. Over time, excessive scaling can compromise the performance of the equipment and may require descaling or maintenance to restore proper function. Thus, the likelihood of an overflow condition as a result of heavy scaling on the tank's internal surfaces is significant, making it the correct answer.