Septic Tank Calculator

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Optimal Flow Distribution

Reduces short-circuiting and ensures proper wastewater treatment

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Improved Sedimentation

Enhanced settling efficiency and better separation of solids

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Better Retention Time

Optimal treatment time for biological processes

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Easier Maintenance

Standard dimensions for construction and access

Building Type

Number of Users/Beds Enter total number of users/beds/students as applicable

Cleaning Interval Frequency of sludge removal (affects sludge storage volume)

Daily Wastewater Calculation

Daily wastewater = Users × Water consumption × 1.0 (100% - Conservative approach)

Peak Flow Rate

Peak flow = (Daily wastewater ÷ 12 hours ÷ 60 minutes) × Peak factor

Surface Area Requirement

Surface area = (Peak flow ÷ 10) × 0.92 m² (IS 2470 Clause 3.4.2.1)

Liquid Volume Calculation

Use larger of: (1) Surface area × 1.0m depth, (2) Daily wastewater × 1 day

Sludge Storage Volume

Larger of: (1) Users × 33 L/capita, (2) Users × 30 L/year × cleaning interval

Total Volume with Safety Factor

Total = (Liquid + Sludge) × 1.2 safety factor, minimum 1000L

3:1 Ratio Dimension Calculation

Plan area = Total volume ÷ liquid depth
Width = √(Plan area ÷ 3), Length = 3 × Width

Tank Dimensions (3:1 Ratio): -

Length:Width Ratio Verification

Total Capacity: -

Plan Area (L×W): -

Surface Area Required: -

Peak Flow Rate: -

Daily Wastewater Flow: -

Sludge Storage Volume: -

✓ Design compliant with IS 2470 & IS 1172 - Fixed 3:1 Length:Width Ratio

Dimensional Requirements (3:1 Ratio)

Length:Width Ratio: 3:1 (FIXED)
Minimum width: 0.75m as per IS 2470
Minimum liquid depth: 1.0m
Freeboard: 0.3m minimum above liquid level
Total depth includes freeboard and bottom clearance

Concrete & Structure

Grade: M15 minimum (1:2:4 mix ratio)
Curing: 12 days minimum with water
Vibration: Machine vibrated concrete
Wall thickness: 200mm brick / 370mm stone
Base slab: 100mm minimum thickness

Waterproofing & Finishing

Plastering: 12mm cement mortar (1:3)
Waterproofing: All internal surfaces
Bituminous coating or membrane
Slope: 1:10 towards sludge outlet
Smooth internal finish

Fittings & Accessories

Vent pipe: 50mm diameter, mosquito mesh
Access: 455×610mm rectangular opening
Cover: RCC with lifting arrangement
Inlet/Outlet: T-junction or baffles
Design optimized for 3:1 ratio layout

3:1 Length:Width Ratio Benefits