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IS 14890:2001 is the Indian Standard (BIS) for general requirements for water supply and drainage systems in buildings. This standard provides general requirements for the design and installation of water supply and drainage systems in buildings. It covers materials, pipe sizing using the fixture unit method, water storage, system layout, traps, venting, and testing to ensure a hygienic and efficient plumbing network. This code works in conjunction with IS 1172 and the National Building Code.
Lays down general requirements for materials, workmanship, testing, and maintenance of water supply and drainage systems in buildings.
Overview
Status
Superseded — superseded by IS 17429:2020 (Part 1 & 2)
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This standard is now largely superseded by the National Building Code (NBC) of India 2016, Part 9 'Plumbing Services', which offers more comprehensive and updated guidelines. It should be used as the primary reference.
! Correctly calculating fixture units (Loading Units) from Table 1 is critical for accurately sizing both supply and drainage pipes.
! Ensuring every fixture has a water-seal trap with adequate seal depth (min. 50 mm) and that the system is properly ventilated is crucial to prevent foul gases from entering occupied spaces.
Comprehensive model code for design, installation, and inspection of all plumbing systems.
BS EN 12056-2:2000British Standards Institution (BSI) / European Committee for Standardization (CEN), UK/Europe
MediumCurrent
Gravity drainage systems inside buildings - Part 2: Sanitary pipework, layout and calculation
Focuses on the calculation, layout, and design of sanitary gravity drainage systems.
AS/NZS 3500.2:2021Standards Australia / Standards New Zealand, Australia/New Zealand
HighCurrent
Plumbing and drainage - Part 2: Sanitary plumbing and drainage
Covers materials, design, and installation for sanitary plumbing and drainage systems.
UPC 2021International Association of Plumbing and Mechanical Officials (IAPMO), USA
HighCurrent
Uniform Plumbing Code
A major model code in the US covering water supply, drainage, and venting systems.
Key Differences
≠The Indian code is primarily based on the Fixture Unit method for sizing drainage pipes, similar to US codes. However, European standards (BS EN 12056) use a more theoretical method based on calculated flow rates in litres/second and Discharge Units (DU).
≠Fixture Unit (FU) values assigned to identical fixtures differ significantly. For example, a standard water closet might be 4-6 FU in the Indian code (NBC Part 9) but only 1.6 FU in the IPC, leading to different pipe sizing outcomes.
≠While the Indian code permits Air Admittance Valves (AAVs), their use is more restricted than in the IPC or BS EN standards, which allow for more flexible and engineered venting solutions.
≠US codes like the IPC provide highly prescriptive tables for maximum trap-arm lengths based on pipe diameter to protect the trap seal, whereas the Indian standard offers more general guidance on achieving self-siphonage prevention.
Key Similarities
≈All standards mandate the use of water seal traps (e.g., P-traps) at every fixture to prevent the ingress of sewer gases into the building.
≈The fundamental principle of using gravity for drainage, requiring minimum gradients or slopes for all horizontal drainage pipes to ensure self-cleansing velocity, is a core concept in all codes.
≈All standards universally require a ventilation system (vent pipes) to protect trap seals against pressure fluctuations (siphonage and back pressure) within the drainage network.
≈All codes require the provision of accessible cleanouts at strategic locations (e.g., changes in direction, base of stacks) to allow for maintenance and removal of blockages.
≈A fundamental principle in all codes is the separation of foul water (from toilets, kitchens, etc.) and surface water (rainwater) drainage systems, although combined systems may be permitted under specific local authority regulations.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum trap seal depth (most fixtures)
50 mm
51 mm (2 inches)
IPC 2021
Minimum slope for 100 mm (4") horizontal drainage pipe
1:100 (1%) minimum, with 1:40 (2.5%) recommended
1:96 or 1/8" per foot (1.04%)
IPC 2021
Fixture Unit value for a private Water Closet (>6 LPF)
4
1.6
IPC 2021
Minimum size of main soil stack receiving a WC
100 mm
76 mm (3 inches)
IPC 2021
Minimum vent termination height above roof
150 mm
152 mm (6 inches)
IPC 2021
Hydrostatic test pressure for water supply system
1.5 times working pressure
1.5 times working pressure, but not less than 100 psi (690 kPa)
IPC 2021
Maximum spacing between manholes/cleanouts on straight runs of underground drains
30 metres
100 feet (30.5 metres) for pipes up to 12 inches
IPC 2021
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Minimum trap seal depth50 mm
Minimum soil pipe diameter for WC100 mm
Minimum recommended slope for 100 mm drain1 in 40
Water supply pipe test pressure1.5 times the maximum working pressure
Minimum height of vent pipe above roof0.3 m
Tables & Referenced Sections
Key Tables
Table 1 - Loading Units for Various Sanitary Fixtures
Table 2 - Sizing of Communication Pipes and Service Pipes on the Basis of Loading Units
Table 7 - Sizing of Soil, Waste and Ventilating Pipes for Discharge from a Single Fixture
It is a factor used to determine the load-producing effect of a sanitary fixture on the plumbing system, which is then used for pipe sizing (Clause 3.16 and Table 1).
What is the minimum diameter for a soil pipe that receives discharge from a water closet (WC)?+
100 mm (Clause 6.2.1.1).
What is the minimum water seal depth for a trap?+
Generally 50 mm for most fixtures. For floor traps or any other trap where loss of seal by evaporation is likely, a 75 mm deep seal is recommended (Clause 6.4.2.1).
What is the recommended gradient for horizontal drainage pipes?+
For 100 mm pipes, a slope of 1 in 40 is recommended to achieve self-cleansing velocity. Steeper slopes can cause solids to be left behind (Clause 6.2.2).