Septic Tank Size Calculator
Calculate the right septic tank size in litres and recommended length-width-depth in meters for any household. Sized for typical Nepali residential usage following IS 2470 guidelines.
How sizing works
We use 100 L per person per day for the liquid component and 30 L per person per year for sludge accumulation. Cleaning every two years is the most common interval for residential homes in Kathmandu Valley. The recommended dimensions assume a length-to-width ratio of 2:1, which is a good balance between efficient settling and space utilisation.
FAQ
What size septic tank do I need for a 5-person family in Nepal?
For a 5-person household with 24-hour detention and 2-year cleaning, the total volume needed is about 800 litres or 0.8 cubic meters. Recommended internal dimensions are roughly 1.65 m × 0.83 m × 1.5 m liquid depth, plus 30 cm freeboard above the liquid line.
How often should a septic tank be cleaned?
In typical Nepali residential use, a septic tank should be desludged every 2 to 3 years. If the tank is undersized for the household, sludge can fill the tank in less than a year, causing slow drainage and odor problems.
What is the minimum liquid depth for a septic tank?
A liquid depth of at least 1.0 metre is recommended so solids can settle properly. 1.2 to 1.8 metres is the typical range for residential septic tanks. Going shallower than 1 metre risks short-circuiting where wastewater flows out before solids can separate.
Where should the septic tank be placed?
Place the tank at least 7.5 metres from any drinking water source like a well or boring, at least 1.5 metres from the building foundation, and away from trees with aggressive roots. Provide an access cover for cleaning and a vent pipe to release gases safely.