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IS 774:2022 is the Indian Standard (BIS) for flushing cisterns for water closets and urinals - specification. This standard specifies the requirements, materials, dimensions, and testing methods for single and dual flushing cisterns used with water closets and urinals. MEP and plumbing engineers use it to ensure water efficiency, durability, and reliable mechanical performance of sanitary flushing systems.
Specifies requirements for flushing cisterns made of plastic and vitreous china, used with water closets and urinals.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Always ensure the flushing cistern's flush volume matches the hydraulic design requirements of the specific WC pan to prevent poor clearing or excessive water waste.
! Dual flush cisterns are highly recommended and often mandated by green building codes (like IGBC or GRIHA) for water conservation.
! Pay special attention to the float valve specifications (IS 1703 or IS 12234) to prevent continuous leakage in high-pressure water supply zones.
plasticsvitreous chinacast ironceramics
International Equivalents
Similar International Standards
EN 14055:2018CEN (Europe)
HighCurrent
WC and urinal flushing cisterns
Dedicated standard for flushing cisterns, covering performance, materials, and testing.
Covers the entire water closet unit (pan and tank); cistern performance is tested as part of the system.
AS 1172.2:2014Standards Australia (Australia)
MediumCurrent
Water closet (WC) pans of 6/3 L capacity or proven equivalent — Part 2: Pans
Focuses on the WC pan, but cistern performance is integral to meeting system flush efficiency tests (WELS scheme).
BS 1125:1987BSI (UK)
HighWithdrawn
Specification for WC flushing cisterns (including dual flush) up to 13 litres capacity
Former British standard specifically for flushing cisterns, now replaced by the European equivalent.
Key Differences
≠IS 774 focuses solely on the cistern, whereas standards like ASME A112.19.2 and AS 1172.2 evaluate the cistern as part of a complete WC system, including waste removal and surface wash tests.
≠EN 14055 includes detailed classification for acoustic performance (noise levels) of the fill and flush cycle, a requirement not specified in IS 774:2022.
≠The American standard is closely linked to the EPA WaterSense program, which promotes high-efficiency toilets (HETs) with a maximum flush of 1.28 gallons (4.8 L), stricter than the common 6 L full flush in IS 774.
≠EN 14055 defines two performance classes (Class 1 and 2) based on flush performance and durability, offering a tiered quality system not present in the pass/fail criteria of IS 774.
Key Similarities
≈All standards specify core performance requirements for flush volume accuracy, ensuring the cistern delivers the intended amount of water for both full and reduced flushes within set tolerances.
≈Mechanical endurance testing of the flush mechanism (outlet valve) and fill valve (inlet valve) is a mandatory requirement across all standards to ensure long-term operational reliability.
≈All standards require the cistern body and components to be made of non-corrosive, non-toxic materials and to pass watertightness tests to prevent leaks.
≈The concept of dual-flush technology, providing a full and reduced flush option for water conservation, is a common feature specified in IS 774 and its international counterparts.
Parameter Comparison
Parameter
IS Value
International
Source
Dual Flush Mechanism Endurance
200,000 cycles
200,000 cycles (for outlet valve)
EN 14055:2018
Single Flush Mechanism Endurance
100,000 cycles
250,000 cycles (for flush valve assembly)
ASME A112.19.2
Inlet Valve Endurance
100,000 cycles
80,000 cycles
EN 14055:2018
Nominal Full Flush Volume
6 L / 4.5 L / 4 L
Max 1.6 gallons (6.0 L)
ASME A112.19.2
Flush Volume Tolerance (Full Flush)
± 0.5 Litres
± 10% of nominal volume
EN 14055:2018
Cistern Body Static Load Test
900 N for 1 hour
300 lbf (≈1334 N) on tank cover
ASME A112.19.2
Acoustic Performance (Noise)
Not specified
Specified and classified (Group I ≤ 20 dB(A))
EN 14055:2018
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
Standard dual flush capacities3/6 Liters or 2/4 Liters
Standard single flush capacities5, 6, or 10 Liters
Endurance test requirement50,000 cycles for flushing mechanism
Float valve operating pressure range0.05 MPa to 1.0 MPa