What percentage should the filter media expand by for proper backwashing of a sand filter?

The correct percentage for the filter media to expand during backwashing of a sand filter is typically between 30% to 50%. This level of expansion is important because it ensures that the sand particles are sufficiently agitated and separated from each other, allowing for effective cleaning of the filter. During backwashing, the flow of water moves in the opposite direction, dislodging accumulated dirt, debris, and contaminants trapped in the filter media.

When for proper backwashing, achieving an expansion within this range helps to remove the impurities without damaging the integrity of the sand itself. If the media expands too little, not enough contaminants are removed, and if it expands too much, the structure of the filter may be compromised, resulting in loss of filtration efficiency. This balance is crucial for maintaining the operational efficiency and longevity of the sand filter system.