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IS 17267:2019 is the Indian Standard (BIS) for greywater recycling systems - code of practice. 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.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
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.
EN 16941-2:2021CEN (European Committee for Standardization), Europe
HighCurrent
On-site non-potable water systems - Part 2: Systems for the use of treated greywater
Provides requirements for the design, installation, operation, and maintenance of greywater treatment and use systems.
BS 8525-1:2010BSI (British Standards Institution), United Kingdom
HighCurrent
Greywater systems - Part 1: Code of practice
Offers recommendations for the design, installation, and maintenance of greywater systems for domestic buildings.
NSF/ANSI 350-2022NSF International / ANSI, USA
MediumCurrent
Onsite Residential and Commercial Water Reuse Treatment Systems
Focuses on evaluating treatment performance of packaged systems rather than a full code of practice for installation.
AS/NZS 1546.4:2016Standards Australia / Standards New Zealand, Australia/New Zealand
HighCurrent
On-site domestic wastewater treatment units - Part 4: On-site domestic greywater treatment systems
Specifies requirements for the design, performance, and testing of on-site domestic greywater treatment systems.
Key Differences
≠IS 17267 explicitly excludes kitchen sink wastewater from its definition of greywater, whereas standards like EN 16941-2 may allow it but categorize it as 'high organic load' greywater requiring more advanced treatment.
≠The Indian standard mandates the use of a tracer dye (Brilliant Blue FCF) in the treated water storage tank for easy identification in case of leaks or cross-connections, a practice that is recommended but not always mandatory in international standards.
≠IS 17267 provides two distinct sets of treated water quality parameters based on end-use: a stricter set for toilet flushing/floor cleaning and a slightly more relaxed set for gardening. Some international standards like NSF/ANSI 350 focus on one primary set of performance criteria for the treatment system itself.
≠IS 17267 is a comprehensive code of practice covering design, installation, and O&M, while standards like NSF/ANSI 350 are primarily product certification standards focused on verifying the performance of packaged treatment plants.
Key Similarities
≈All standards emphasize the fundamental principle of preventing cross-connection between recycled greywater and potable water systems, requiring physical air gaps or approved backflow prevention devices.
≈There is a common requirement across all standards for clear labeling and color-coding of greywater piping (typically purple/lilac) to distinguish it from potable water and drainage pipes.
≈All standards recommend that raw, untreated greywater be collected and treated promptly, typically within 24 hours, to prevent it from becoming septic and odorous.
≈The general treatment train approach—consisting of primary filtration/screening, secondary biological treatment, and tertiary disinfection—is a common framework in IS 17267 and its international counterparts.
≈All codes require a mechanism for automatic diversion of excess greywater flow (or during system failure) to the sanitary sewer or an approved drainage system.
Parameter Comparison
Parameter
IS Value
International
Source
BOD₅ (for toilet flushing)
< 10 mg/L
< 10 mg/L (as CBOD₅)
NSF/ANSI 350 (Class C/R)
Turbidity (for toilet flushing)
< 2 NTU
< 2 NTU
EN 16941-2 (Example for high quality)
E. coli (for toilet flushing)
Not detectable in 100 ml
< 10 CFU/100ml (Guidance for toilet flushing)
BS 8525-1:2010
pH Range
6.5 - 8.5
6.0 - 9.0
NSF/ANSI 350
Residual Chlorine
0.5 to 1.0 mg/L (if chlorination is used)
Min 0.5 mg/L (if chlorination is used)
BS 8525-1:2010
Max Raw Greywater Storage Time
< 24 hours
< 24 hours
BS 8525-1:2010
Pipe Colour Identification
Lilac (Purple), RAL 4001
Purple (Lilac)
AS/NZS 1546.4 / California Plumbing Code
Total Suspended Solids (TSS)
< 10 mg/L (for flushing)
< 10 mg/L
NSF/ANSI 350 (Class C/R)
⚠ Verify details from original standards before use
Key Values6
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)
Tables & Referenced Sections
Key Tables
Table 1 - Classification of Greywater Sources
Table 2 - End Uses of Treated Greywater
Table A.1 - Permissible Limits for Treated Greywater for Non-potable End Uses
Table B.1 - Per Capita Greywater Generation in Residential Buildings
Key Clauses
Clause 5 - Sources of Greywater
Clause 6 - Design and Installation Considerations
Clause 7 - Greywater Treatment Systems
Clause 11 - Operation and Maintenance
Annex A - Permissible Limits for Treated Greywater for Non-potable End Uses
What sources of water are considered greywater by this code?+
Water from baths, showers, hand basins, and washing machines. Kitchen sink and toilet water (blackwater) are excluded (Clause 5).
What can treated greywater be used for?+
Only for non-potable uses like toilet flushing, floor washing, car washing, and subsurface irrigation. It must not be used for drinking, cooking, or personal bathing (Table 2).
What is the required quality for greywater to be used in toilet flushing?+
Key parameters include pH 6.5-8.5, Turbidity < 2 NTU, and BOD < 10 mg/L. It should also be free from unpleasant odour (Table A.1).
Is a separate plumbing system required for greywater?+
Yes, a completely separate and clearly identified dual plumbing system is required for collecting greywater and distributing the treated water to prevent any cross-connection with the potable water system (Clause 6.4).