Estimate required wastewater treatment design flow from current average flow, peak factor, projected growth, and infiltration allowance. The tool reports average future flow, peak design flow, added capacity, and utilization of an existing plant rating. Use it for early capacity planning before detailed hydraulic and process design.
Peak design flow is a screening requirement based on the entered assumptions. Ensure the plant rating used for comparison is defined on the same basis—peak hourly, peak daily, or another permit/design criterion.
Final design must also evaluate pollutant loads, unit-process limits, redundancy, wet-weather events, collection-system hydraulics, and permit conditions.
A current average flow of 1.2 MGD growing 20% becomes 1.44 MGD. Adding 0.15 MGD infiltration gives a future average of 1.59 MGD. At a 2.5 peak factor, required peak design flow is 3.975 MGD, or 113.6% of a 3.5 MGD comparable plant rating.
Not in this calculator. Growth applies to current average flow, and the entered infiltration allowance is then added separately.
Enter a rated capacity defined on the same peak-flow basis as the calculated requirement.
No. Peak flow cannot be below the calculated future average under this design approach.
Yes. All flow inputs and results on this page use million gallons per day.
No. Hydraulic capacity and treatment loading must both be checked during facility planning.
| Flow element | Calculation | Planning role |
|---|---|---|
| Grown base flow | Current × (1 + growth) | Future sanitary flow |
| Future average | Grown base + infiltration | Average design basis |
| Peak design | Future average × peak factor | Hydraulic requirement |
| Utilization | Peak ÷ plant rating | Capacity screen |