This code establishes the design criteria, dimensions, and construction guidelines for septic tanks used for domestic wastewater treatment. It includes standardized sizing tables based on user population and specifies functional requirements for inlets, outlets, baffles, freeboard, and ventilation.
Provides guidance on the design, location, and construction of septic tanks for domestic and institutional uses.
Quick Reference Values
Minimum capacity1000 litres
Minimum width750 mm
Minimum depth below water level1000 mm
Minimum freeboard300 mm
Length to width ratio2 to 4 times the width
Minimum vent pipe diameter50 mm
Desludging interval1 to 2 years
Practical Notes
Septic tanks only provide primary treatment; effluent must be disposed of via secondary treatment like soak pits or dispersion trenches (covered in Part 2).
Baffle walls or dip pipes must extend at least 150 mm above the liquid level and penetrate into the liquid to prevent scum and sludge wash-out.
Ventilation pipes must be extended at least 2 meters above the building roofline to safely disperse noxious and explosive gases.