Filtration Rate & Backwash Rate Calculator
Filter loading, backwash rate, bed rise rate and backwash water use — for rapid sand and multimedia filters.
Formulas
Filtration rate (gpm/ft²) = flow (gpm) ÷ filter area (ft²)
Backwash rate (gpm/ft²) = backwash flow (gpm) ÷ filter area (ft²)
Rise rate (in/min) = backwash rate × 12 ÷ 7.48
Backwash volume (gal) = backwash rate × area × duration (min)
Typical rapid sand: filtration 2–4 gpm/ft² · backwash 15–20 gpm/ft².
Filtration rate (gpm/ft²) = flow (gpm) ÷ filter area (ft²)
Backwash rate (gpm/ft²) = backwash flow (gpm) ÷ filter area (ft²)
Rise rate (in/min) = backwash rate × 12 ÷ 7.48
Backwash volume (gal) = backwash rate × area × duration (min)
Typical rapid sand: filtration 2–4 gpm/ft² · backwash 15–20 gpm/ft².