Septic Tank Volume Calculator
Size a septic tank from the number of residents, daily water use and required retention time, honouring the EU 3-day minimum of 200 L/person/day.
How to Use the Septic Tank Volume Calculator
- Enter the number of permanent residents.
- Enter the daily water use per person (150–200 L is typical).
- Enter the required retention time (usually 3 days).
- Click Calculate.
Use Cases
- •Private home sanitation design.
- •Rural cottage projects.
- •Utility connection planning.
Formula
V ≥ max(persons × 200 × 3, persons × daily_water × retention_days) litres.
Frequently Asked Questions
Why 200 L/person/day?
European and Russian standards assume 150–200 L per person per day for a home with full plumbing. Cottages without baths can use 100–150 L.
What retention time?
A classic two-chamber septic tank needs at least 3 days retention; biological treatment plants manage with shorter times but also require aeration and electricity.
Does this size leach fields?
No. Leach fields and filter beds need separate calculations that depend on soil percolation, groundwater depth and local regulations.