Code of practice outlining the design criteria, sizing, and construction details for septic tanks used in domestic wastewater primary treatment. It specifies dimensions, capacities based on user load, and structural practices to ensure watertight and efficient anaerobic digestion.
Provides guidelines for the design criteria and construction practices for domestic septic tanks.
Quick Reference Values
minimum liquid capacity1000 litres
minimum width750 mm
minimum liquid depth1.0 m
minimum freeboard300 mm
minimum vent pipe diameter50 mm
sludge accumulation rate30 litres/capita/year
Key Formulas
Total Volume = Liquid retention volume + Sludge storage volume + Scum storage volume
Practical Notes
Baffles or tee-fittings are essential at both inlets and outlets to prevent scum from escaping and clogging the soak pit.
The tank must be thoroughly waterproofed/plastered to prevent groundwater pollution and leakage.
The ventilation pipe must extend at least 2m above ground level or higher than the highest building roof to safely dissipate methane and foul gases.