Filter Loading Rate and Backwash
Loading rate, backwash flow, and rapid-sand vs high-rate category.
Example
You enter
- Filter area (ft²) 100
- Flow (GPM) 300
- Backwash rate (gpm/ft²) 15
You get
- Loading rate 3.00 gpm/ft^2
- Backwash flow 1,500 GPM
Checked against published worked examples from: USEPA.
Details, formula, and sources
Formula or tableLoading rate (gpm/ft²) = filter_flow / filter_area. Backwash flow = backwash_rate × area. Categories: rapid sand 2-5 gpm/ft², high-rate 5-8 gpm/ft².
Source and editionTen 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.
Free accessTen States Standards licensed; principles free in published water-treatment texts.
What governsEstimate. Operator of record and primacy agency govern.
API field namesfilter_area_ft2, flow_gpm, backwash_rate_gpm_ft2, loading_gpm_per_ft2, backwash_gpm
- Default backwash rate 15 gpm/ft² unless user suppliesTen States Standards typical