💧 Wastewater Calculator
Estimate how much wastewater a household or facility generates each day based on the number of occupants and typical water use.
What this calculator does
This calculator estimates the volume of wastewater a household or small facility sends to a septic system or sewer, based on the number of occupants and typical daily water use per person.
How the math works
Environmental engineering guidance commonly estimates indoor water use per person at roughly 60-100 gallons per day, and notes that not all of that water becomes wastewater since some is lost to evaporation, irrigation, or isn’t drained (the ‘return-to-sewer’ factor, typically 85-95% for typical households). The calculator multiplies occupants by water use per person to get total daily water use, then applies the return factor to estimate actual wastewater volume, and scales that to weekly and annual totals.
Actual wastewater generation varies with fixtures, appliances, habits, and season, so this is a general planning estimate, useful for septic sizing conversations or water-use awareness, not a substitute for a professional site evaluation.