Texas TCEQ Class C Water License Practice

Backwashing a rapid sand filter is primarily determined by the loss of head, which indicates the pressure loss across the filter media due to the accumulation of dirt and debris. When the loss of head gauge indicates a range of 6 to 10 feet, it signifies that the filter is becoming clogged and is no longer able to operate efficiently.

At this point, backwashing is necessary to restore the filter’s performance by removing the trapped particles and clearing the pathways through the filter media. This process ensures that the filter can continue to effectively remove contaminants from the water.

The other choices are not accurate indicators for backwashing. A pressure drop below 4 feet may not be sufficient to warrant backwashing, as some filters can operate effectively at lower pressure losses. Simply having clogged media or a complete tank might not provide the direct indication needed for backwashing, making the specified loss of head gauge the correct criteria in this context.