Sewage Flow Rate Calculator Formula
Understand the math behind the sewage flow rate calculator. Each variable explained with a worked example.
Formulas Used
Average Daily Flow
avg_daily_flow = avg_dailyPeak Hourly Flow
peak_hourly_flow = avg_daily / 24 * peak_factorPeak Minute Flow
peak_gpm = avg_daily / 24 / 60 * peak_factorVariables
| Variable | Description | Default |
|---|---|---|
occupants | Number of Occupants(people) | 50 |
per_capita_gpd | Per Capita Flow(gal/day) | 80 |
peak_factor | Peak Hour Factor | 2.5 |
avg_daily | Derived value= occupants * per_capita_gpd | calculated |
How It Works
Sewage Flow Estimation
Average Daily Flow = Occupants x Per Capita GPD
Peak Flow = Average / 24 x Peak Factor
Residential per-capita wastewater is typically 60 to 100 gallons per day. The peak-hour factor (2 to 4 for residential, up to 5 for commercial) accounts for the morning and evening surges.
Worked Example
50 occupants, 80 gal/day each, peak factor 2.5.
occupants = 50per_capita_gpd = 80peak_factor = 2.5
- 01Avg daily = 50 x 80 = 4,000 gal/day
- 02Avg hourly = 4,000 / 24 = 167 gal/hr
- 03Peak hourly = 167 x 2.5 = 417 gal/hr
- 04Peak GPM = 417 / 60 = 6.9 GPM
Ready to run the numbers?
Open Sewage Flow Rate Calculator