A filter backwash cycle for a sand filter is considered complete when:

The completion of a filter backwash cycle for a sand filter is determined by the clarity of the backwash water. When the backwash water appears clear in the sight glass, it indicates that the filter media has been effectively cleaned of accumulated debris and contaminants. During backwashing, the water flow direction is reversed, which dislodges trapped particles from the sand and flushes them out of the system.

Seeing clear water signifies that the filter is no longer releasing impurities and is likely functioning optimally, ready to return to its normal filtration process. This visual confirmation is crucial because it offers a direct measure of filter cleanliness, ensuring that the water quality is maintained for pool users.