Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 11729:1985 Part 1 is the Indian Standard (BIS) for plumbing services in buildings, part 1: general requirements. This code provides general requirements for plumbing services in buildings. It covers the design and installation of water supply systems, including pipe sizing, storage, and distribution, as well as drainage systems for soil and waste. The standard focuses on ensuring functional, safe, and hygienic plumbing installations.
Covers general requirements, definitions, and basic principles for plumbing services within buildings.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Although still in use, this standard is dated. It is highly recommended to refer to the latest version of the National Building Code (NBC) of India, Part 9 - Plumbing Services, which provides more current and comprehensive guidelines.
! The Fixture Unit method (both WSFU for supply and DFU for drainage) is the core principle for pipe sizing in this code. Accurate calculation is critical.
! Proper venting of the drainage system as per code guidelines is crucial to protect trap seals and ensure smooth flow.
Both are comprehensive codes establishing minimum requirements for plumbing systems, including water supply, drainage, fixtures, and venting.
AS/NZS 3500.1:2021 & AS/NZS 3500.2:2021Standards Australia / Standards New Zealand
HighCurrent
Plumbing and drainage, Part 1: Water services & Part 2: Sanitary plumbing and drainage
Collectively, these standards cover the same scope as IS 11729, detailing requirements for water supply and sanitary drainage systems.
BS EN 12056 Series & BS EN 806 SeriesBritish Standards Institution (BSI) / European Committee for Standardization (CEN), UK/Europe
MediumCurrent
Gravity drainage systems inside buildings & Specifications for installations inside buildings conveying water for human consumption
This series of standards covers the scope of IS 11729 but is split into multiple, more detailed parts for drainage and water supply.
UPC 2021International Association of Plumbing and Mechanical Officials (IAPMO), USA
HighCurrent
Uniform Plumbing Code
Provides regulations for the installation and inspection of plumbing systems, covering a nearly identical scope to IS 11729.
Key Differences
≠IS 11729:1985 has very limited guidance on water conservation. Modern international codes like the IPC mandate low-flow fixtures, specifying maximum flush volumes for toilets (e.g., 1.6 gpf) and flow rates for faucets and showerheads.
≠Modern international codes have extensive, prescriptive requirements for backflow prevention based on a detailed hazard classification system. IS 11729 provides only general principles for preventing back-siphonage, lacking specifics on modern devices like RPZ or DCVA.
≠IS 11729 references materials common in 1985 like Galvanized Iron (GI) and Cast Iron (CI). International codes include a much broader range of approved modern materials such as PEX, CPVC, and polypropylene, with detailed joining and support standards.
≠Modern codes like the IPC permit the use of Air Admittance Valves (AAVs) as an alternative to traditional atmospheric venting in many situations. IS 11729:1985 does not recognize or provide guidance for AAVs, focusing solely on conventional vent pipes.
Key Similarities
≈All codes are founded on the same fundamental principles: to supply safe, potable water, prevent cross-contamination, and ensure the sanitary and safe removal of wastewater and sewage.
≈Both IS 11729 and international codes universally mandate the installation of a water seal trap at every plumbing fixture to block the entry of sewer gases into occupied spaces.
≈All standards require the complete separation of the water supply distribution system from the sanitary drainage system to prevent contamination of potable water.
≈The core concept of requiring a vent system to protect trap seals from siphonage and back-pressure is a fundamental and shared requirement across IS 11729 and all major international plumbing codes.
≈The requirement for providing accessible cleanouts at specified intervals and at changes in direction in the drainage system is a common feature for maintenance purposes.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Air Gap for Water Outlet
20 mm or twice the pipe diameter, whichever is greater.
Not less than 1 inch (25.4 mm) or twice the diameter of the effective opening.
IPC 2021
Minimum Trap Seal Depth
50 mm for most non-floor traps.
Not less than 2 inches (51 mm) and not more than 4 inches (102 mm).
IPC 2021
Maximum Water Closet (WC) Flush Volume
10 litres (for single flush).
1.6 gallons per flush / 6 litres per flush.
IPC 2021
Minimum Slope for 100mm (4-inch) Horizontal Drain
1 in 40 (2.5% grade) is recommended.
1/4 inch per foot (2% grade). 1/8 inch per foot (1%) is permissible in some cases.
IPC 2021
Minimum Water Pressure at Fixture Outlet
0.018 N/mm² (approx. 1.84 meters of head).
8 psi (approx. 5.63 meters of head) for most fixtures.
IPC 2021
Maximum Spacing for Cleanouts (Horizontal Drains)
Not more than 30 meters.
Not more than 100 feet (30.48 meters).
IPC 2021
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Minimum domestic water storage (full flushing)135 to 200 litres/capita/day
Minimum water seal depth in traps50 mm
Minimum water seal depth in floor traps75 mm
Minimum slope for 100mm horizontal drainage pipe1 in 100
Hydrostatic test pressure for water pipes1.5 times working pressure or 6 kg/cm², whichever is greater
Tables & Referenced Sections
Key Tables
Table 1 - Fixture Units for Different Sanitary Fixtures for Domestic Use (Drainage)
Table 2 - Soil Pipes and Waste Stacks Serving Fixture Units
Table 10 - Water Supply Fixture Units (WSFU) for Various Fixtures