What does an elevated reading on the vacuum gauge of a high rate sand filter indicate?

An elevated reading on the vacuum gauge of a high-rate sand filter indicates that the filter is experiencing increased resistance to the flow of water, typically due to a buildup of debris and contaminants trapped in the sand media. This accumulation of materials prevents water from passing through as efficiently as it should, leading to the elevated pressure reading on the gauge.

When the pressure in the filter increases significantly above the normal operating range, it indicates that the filter media is clogged and has reached its capacity, signifying that it is time to backwash the filter. Backwashing is the process of reversing the flow of water through the filter to dislodge and remove trapped debris, allowing the filter to operate effectively again. By performing a backwash, the filter's efficiency is restored, and it can continue to effectively clean the pool water.