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The above chart shows us that the headloss through an expanded bed is constant once fluidization is achieved and, for a 5 cm filter bed, it ranges around 0.7 cm. According to Okun and Schulz's equation, a 5 cm filter bed with porosity of 0.4 and specific gravity of 1.92 should have a headloss of 2.76cm. Despite the difference between actual and calculated headloss, it is a positive discovery that headloss through an expanded bed stays constant once fluidization occurs. We can easily estimate all of the headloss occurring in our backwash system to properly position the elevation of the clear well between the sedimentation tank and the filter beds.