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IS 11925:1986 is the Indian Standard (BIS) for pitch-impregnated fibre pipes and fittings for drainage purposes. This standard specifies the requirements for materials, dimensions, manufacture, and performance tests for pitch-impregnated fibre pipes and associated fittings. These components are intended for use in underground non-pressure drainage, sewerage systems, and as conduits for cables.
pitch-impregnated fibre pipes and fittings for drainage purposes
! These pipes are lightweight and easy to handle but can be brittle and require careful bedding and backfilling to prevent crushing.
! This material technology is largely superseded by modern plastics like PVC and HDPE, which offer better durability, chemical resistance, and jointing integrity.
! Joints are typically made with taper-fit couplings, requiring proper alignment and force to ensure a tight seal.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
pitch-impregnated fibrebitumencellulose fibre
International Equivalents
Similar International Standards
BS 2760:1973BSI (British Standards Institution), UK
HighWithdrawn
Specification for pitch-impregnated fibre pipes and fittings for drainage below and above ground
Covers the same material (pitch-impregnated fibre) for identical drainage applications.
ASTM D1861-94 (1998)ASTM International, USA
HighWithdrawn
Standard Specification for Homogeneous Bituminized Fiber Drain and Sewer Pipe
Specifies requirements for homogeneous bituminized fiber pipes used for drainage and sewerage.
CAN/CSA-B58.1-M90CSA Group, Canada
HighWithdrawn
Bituminized-Fibre Drain and Sewer Pipe
Specifies materials, dimensions, and performance for Canadian bituminized-fibre sewer pipes.
SABS 921:1969SABS (South African Bureau of Standards), South Africa
HighWithdrawn
Standard specification for pitch-impregnated fibre drain and sewer pipes and fittings
Covers the requirements for pitch-impregnated fibre pipes in the South African context.
Key Differences
≠ASTM D1861 and its companion standard ASTM D1862 differentiate between 'Homogeneous' and 'Laminated-Wall' pipes, respectively. IS 11925 does not make this explicit distinction in its classification.
≠While chemical resistance tests are common to all standards, the specific reagents, concentrations, and immersion times can vary. IS 11925 specifies tests against sulphuric acid, sodium carbonate, and sodium sulphate.
≠Dimensional classes and nominal sizes are based on regional practices. IS 11925 uses metric sizes (e.g., 75, 100, 150 mm), whereas BS and ASTM standards originally used imperial sizes (e.g., 3, 4, 6 inches) which were later metricated.
Key Similarities
≈All standards cover the same fundamental product: a pipe made from cellulose fibres saturated with coal tar pitch or bitumen for use in non-pressure drainage systems.
≈The primary performance tests are conceptually identical across the standards, including crush strength (to resist soil load), water absorption (to ensure impermeability), and flattening tests (to ensure structural integrity).
≈The jointing methodology is consistent, relying on machined tapered ends on pipes and corresponding tapered sockets on couplings or fittings to create a tight, root-resistant interference fit.
≈All these standards are largely obsolete and have been withdrawn in their respective countries, as pitch-impregnated fibre has been superseded by more durable materials like PVC, HDPE, and ductile iron.
Parameter Comparison
Parameter
IS Value
International
Source
Water Absorption (max % by weight)
≤ 2.0%
≤ 2.0%
ASTM D1861
Dry Crushing Strength (min, 100 mm / 4" pipe)
16.0 kN/m
16.1 kN/m (equivalent of 1100 lbf/ft)
BS 2760:1973
Flattening Test (compression)
No cracking when compressed to 40% of original diameter
No cracking when compressed to 40% of original diameter
ASTM D1861
Heat Resistance (Boiling Water Test)
No blistering/delamination after 6 hrs in water at 80°C
No blistering/flattening after immersion in water at 82°C (180°F)
ASTM D1861
Beam Strength (100 mm / 4" pipe)
90 kgf (883 N) centre load
1000 lbf (4448 N) total load on 2 point loading, which is a different test method
ASTM D1861
Alkali Resistance
Immersed in 0.5% Sodium Carbonate solution, must not fail subsequent crushing test.
Immersed in 0.1 N Sodium Carbonate / Hydroxide solution, must not fail subsequent crushing test.
ASTM D1861
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Minimum dry crushing strength (100 mm pipe)2.0 kN/m
Minimum wet crushing strength (100 mm pipe)1.0 kN/m
Maximum water absorption (48h immersion)2.0 percent by mass
Heat resistance test temperature80 ± 2 °C
Boiling water resistanceNo evidence of disintegration after 6 hours
Kerosene resistanceNo delamination or disintegration after 24 hours
What are the primary applications of pitch-impregnated fibre pipes?+
They are used for underground, non-pressure applications such as building drainage, land drainage, and sewerage (Clause 1.1).
What is the key strength requirement for these pipes?+
The dry crushing strength, which ensures the pipe can withstand soil and traffic loads when buried. The minimum value varies with pipe diameter (Table 3).
Are these pipes resistant to common chemicals found in sewage?+
Yes, the standard includes tests for resistance to dilute sulphuric acid, sodium carbonate, and sodium sulphate to ensure durability in typical drainage environments (Clause 7).
How is jointing performed between two pipes?+
Joints are made using separate couplings of the same material. The ends of the pipes and the inside of the couplings are tapered to form a drive-tight joint (Clause 5.1).