Minnesota Class D Water Operator Certification Practice Exam 2025 - Free Water Operator Practice Questions and Study Guide

Backwashing a filter is an important maintenance procedure that helps to ensure its effective operation. Doing this when there is high head loss is the correct approach because it indicates that the filter media is becoming clogged with particles and debris. High head loss occurs when there is a significant increase in pressure required to push water through the filter due to the accumulation of contaminants. This condition suggests that the filter is not operating efficiently, which can lead to compromised water quality.

By backwashing the filter, water is flowed in the opposite direction, dislodging trapped particles and allowing for their removal from the system. This process restores the filter's efficiency and helps maintain optimal performance.

Other options, while relevant in a broad sense, do not provide the best criteria for determining when to backwash. For example, a filter being clogged or less than half full do not necessarily indicate that immediate backwashing is required, and filters that are new typically do not require backwashing as they have not yet become loaded with contaminants. Therefore, monitoring head loss is the most effective guideline for scheduling backwashing activities.