What is the recommended expansion percentage for a mixed media filter bed during backwash?

The recommended expansion percentage for a mixed media filter bed during backwash is 25%. This percentage is crucial for effective backwashing, as it allows for sufficient separation of the media grains without leading to excessive loss of filter media.

When backwashing, the water flow must be strong enough to lift the media and remove trapped particles, but not so strong that it causes media to be lost or the layers to become unbalanced. A 25% expansion ensures that the backwash water effectively cleans the filter bed, allowing for the removal of accumulated solids while maintaining the media's integrity and arrangement. It strikes a balance between achieving thorough cleaning and preventing damage or displacement of the filter media.

Understanding the importance of maintaining the correct expansion percentage is vital in achieving optimal filtration performance and prolonging the life of the filter system.