This standard provides guidelines for the planning, design, installation, operation, and maintenance of greywater recycling systems. It classifies greywater sources, specifies treatment requirements, and defines the quality standards for treated water intended for non-potable uses like toilet flushing and irrigation.
Provides guidelines for the design, installation, operation, and maintenance of greywater recycling systems in buildings.
Quick Reference Values
Max storage time for untreated greywater24 hours
pH range for treated water for toilet flushing6.5 - 8.5
Max BOD for treated water for toilet flushing10 mg/L
Max Turbidity for treated water for toilet flushing2 NTU
Max Total Coliforms for surface irrigation1000 MPN/100 ml
Residual chlorine for treated water0.5 mg/L
Key Formulas
Greywater generated (litres/day) = No. of users × Per capita greywater generation rate (lpcd)
Practical Notes
Untreated greywater should not be stored for more than 24 hours to prevent it from turning septic and odorous.
It is crucial to avoid cross-contamination between the greywater system and the potable water supply. Use distinct pipe colours (e.g., purple) and labels as specified.
Kitchen sink water should be excluded from greywater collection systems due to its high content of organic matter, oil, and grease, which makes treatment more difficult.