Septic Tank Size Calculator
Estimate septic tank dimensions based on number of users and desludging interval.
India reference sizing based on CPHEEO guidance and IS 2470 design framework
Enter the expected number of users and select the planned cleaning
interval. The calculator selects the next applicable published
CPHEEO reference size so that an intermediate population is not
assigned a smaller standard tank.
Reference sizing in this calculator covers up to 300 users.
Longer intervals require additional sludge-storage depth.
Recommended Reference Tank Dimensions
–
Approx. Liquid Volume
Total Internal Depth
Freeboard
0.30 m
Length : Breadth Ratio
View CPHEEO Reference Septic Tank Sizes
| Users | Length | Breadth | Liquid Depth 2 yr |
Liquid Depth 3 yr |
|---|---|---|---|---|
| 5 | 1.50 m | 0.75 m | 1.00 m | 1.05 m |
| 10 | 2.00 m | 0.90 m | 1.00 m | 1.40 m |
| 15 | 2.00 m | 0.90 m | 1.30 m | 2.00 m |
| 20 | 2.30 m | 1.10 m | 1.30 m | 1.80 m |
| 50 | 5.00 m | 2.00 m | 1.00 m | 1.24 m |
| 100 | 7.50 m | 2.65 m | 1.00 m | 1.24 m |
| 150 | 10.00 m | 3.00 m | 1.00 m | 1.24 m |
| 200 | 12.00 m | 3.30 m | 1.00 m | 1.24 m |
| 300 | 15.00 m | 4.00 m | 1.00 m | 1.24 m |
Septic Tank: A septic tank is a watertight onsite sanitation unit that retains wastewater long enough for settleable solids to form sludge and lighter materials to form scum, while partially clarified effluent is discharged for further treatment or disposal.
Reference basis: CPHEEO Manual on Sewerage and Sewage Treatment
Systems, Part A – Engineering (2013); IS 2470 (Part 1):1985,
Code of Practice for Installation of Septic Tanks; and MoHUA/SBM
Urban technical guidance. Results are intended for preliminary
sizing only. Final septic tank and effluent disposal design should
follow applicable local authority requirements, site conditions,
wastewater characteristics and detailed engineering calculations.