Which of the following indicates that a pool filter needs cleaning?

A higher pressure reading on a pool filter gauge is a key indicator that the filter requires cleaning. As the filter traps dirt, debris, and contaminants, the resistance to water flow increases. This increased resistance results in a higher pressure reading on the pressure gauge, signaling that the filter is becoming clogged and needs maintenance. Regular monitoring of this pressure reading is essential for maintaining optimal filtration efficiency and ensuring that the pool water remains clean and safe for users.

The other options do not correlate with the need for filter cleaning. Increased water clarity may suggest that the filtration system is working effectively, while a lower water level might indicate evaporation or leaks rather than filter maintenance needs. Cooler water temperature does not influence the filter’s performance and thus is not a relevant factor for determining cleaning necessity.