Filter Loading Rate and Backwash

Loading rate, backwash flow, and rapid-sand vs high-rate category.

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Formula and source

Loading rate (gpm/ft²) = filter_flow / filter_area. Backwash flow = backwash_rate × area. Categories: rapid sand 2-5 gpm/ft², high-rate 4-8 gpm/ft².

Ten States Standards (Recommended Standards for Water Works), Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers, current edition by name. AWWA B100 / B130 (filter media) by name.

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