Which of the following can be an indicator of a blockage in a water system?

Lower than normal water usage rates can indeed indicate a blockage in a water system. When there is a blockage, the normal flow of water is restricted, which can lead to a decrease in water usage rates. This situation may occur because the water cannot move freely through the pipes, causing less water to reach the taps and appliances normally utilizing it. In residential or commercial settings, significant drops in water usage can raise concerns regarding the integrity and functionality of the water distribution system.

The other options, while they can indicate various issues within a water system, do not specifically point to a blockage. Constant high water pressure readings may suggest a pressure issue but does not directly correlate with a blockage. Dripping faucets are often a sign of worn-out washers or seals rather than blockages. Sudden increases in water temperature generally indicate a malfunctioning water heater or changes in the water supply source rather than a blockage in the piping system itself.