Overview

What This Standard Covers

IS 11925:1986 specifies requirements for pitch-impregnated fibre pipes and fittings used primarily for drainage purposes, including perforated pipes for sub-surface drainage. This standard covers materials, dimensions, joint types, mechanical and chemical performance tests, and marking requirements to ensure durability, water-tightness, and suitability for various drainage applications. It is intended for manufacturers, engineers, and quality controllers involved in the production, installation, and inspection of drainage piping systems.

Audience

Who Uses This Standard

Civil Engineers
Sanitary Engineers
Quality Control Inspectors
Manufacturers of Fibre Pipes and Fittings
Public Health Engineers
Drainage System Designers
Construction Project Managers

Contents

Key Topics Covered

✓Material specifications for pitch-impregnated fibre pipes

✓Dimensions and tolerances of pipes and fittings

✓Types of joints including spigot and socket, taper coupling, snap ring, and 'O' ring joints

✓Mechanical performance tests such as crushing strength, beam strength, and impact resistance

✓Chemical resistance tests including boiling water and kerosene immersion

✓Requirements for perforated pipes used in sub-surface drainage

✓Fabrication and adhesive testing for fittings

✓Water-tightness and leakage tests for joints

✓Marking and certification requirements

✓Installation considerations and joint flexibility

✓Standardized testing procedures and apparatus

✓Quality assurance and compliance criteria

Structure

0Introduction▼

IS 11925: Introduction - Key Specifications & Tables

Material (Clause 6.3):
Polypropylene fittings must be black, made from isotactic polypropylene polymer or copolymer with stabilizers, lubricants, fillers.
Minimum body wall thickness is per Table 6 (not fully provided here).

Key Tables Summary:

Table	Description	Nominal Bore (mm)	Key Dimensions
2	Taper Coupling Joints (Clause 5.2)	50 to 225	Coupling length (L), Pipe joint length (F), Gap (G), Wall thickness (T), Diameter inside large end
3	Snap Ring Joints (Clause 5.3)	75 to 150	Mid zone diameters (D1, D2, D3), Insertion depth (L1), Ring seal depth (L2), Lead-in (a), Thickness (T)
4	'O' Ring Joints (Clause 5.4)	100, 150	Internal diameter (G), Coupling thickness (H), Groove dimensions (A, C), Socket length (K), Distance register (D3)
5	Spigot and Socket (Clause 5.5)	50 to 225	Length of spigot (F)

Example: Taper Coupling Joint Dimensions (Table 2)

Nominal Bore (mm)	Coupling Length L (min-max, mm)	Pipe Joint Length F (mm)	Gap G (min-max, mm)	Coupling Wall Thickness T (Polypropylene, mm)
50	73.7 - 76.2	36.3	6.4 - 12.7	3.8
100	99.6 - 102.1	49.3	6.4 - 12.7	4.6
150	99.6 - 102.1	49.3	6.4 - 12.7	6.9
225

1Scope▼

IS 11925 - Scope: Key Specifications & Tables Summary

Scope: Covers dimensions, materials, and tolerances for polypropylene pipes and fittings used in pressure applications.

Key Tables & Specifications:

1. Material & Fittings (Clause 6.3)

Polypropylene fittings: Black, isotactic polypropylene polymer/copolymer.
Minimum body wall thickness per Table 6 (not fully shown here).

2. Pipe Dimensions (Clause 4.1.2, Table 1)

Nominal Bore (mm)	Min Internal Dia. (mm)	Max Internal Dia. (mm)
50	50	54
75	75	80
100	100	106
125	125	133
150	150	160
200	200	213
225	225	239

3. Taper Coupling Joints (Table 2)

Coupling length (L): Varies by bore, e.g., 50 mm bore: 73.7–76.2 mm.
Pipe joint length (F): e.g., 50 mm bore: 36.3 mm (±0.25 mm).
Gap at initial contact (G): e.g., 50 mm bore: 6.4–12.7 mm.
Wall thickness (T):
- Impregnated fibre: 6.4 mm (min for 50 mm bore).
- Polypropylene tapered ends: 3.8 mm (min for 50 mm bore).

4. Snap Ring Joints (Table 3)

Mid zone diameters (Socket DI, Throat D2).
Insertion depth (LI), ring seal depth (L2).
Lead-in (a), thickness (T), outside pipe diameter (D+).

5. O-Ring Joints (Table 4)

Internal diameter (G), coupling thickness (H).
Groove dimensions (width A, diameter C).
Socket length (K), distance

2Definitions▼

IS 11925: Key Definitions and Specifications

1. Definitions (Clause 2.0)

Standard definitions apply for pipe fittings, joints, and materials used.
Polypropylene fittings (Clause 6.3) are black, made from isotactic polypropylene with stabilizers, lubricants, fillers.
Minimum body wall thickness as per Table 6.

2. Important Tables Summary

Table	Description	Key Parameters
Table 2	Taper Coupling Joints (Clause 5.2)	Coupling length (L), Pipe joint length (F), Gap at initial contact (G), Wall thickness (T), Diameter inside large end, Wall thickness at male end
Table 3	Snap Ring Joints (Clause 5.3)	Socket diameter (D1), Throat (D2), Distance register (D3), Insertion depth (L1), Ring seal depth (L2), Lead in (a), Thickness (T), Pipe outside diameter (D+)
Table 4	'O' Ring Joints (Clause 5.4)	Internal coupling diameter (G), Coupling thickness (H), Groove diameter (C), Groove width (A), Socket length (K), Distance register (D3)
Table 5	Spigot and Socket (Clause 5.5)	Spigot length (F) with tolerance

3. Example: Taper Coupling Joint Dimensions (Table 2)

Nominal Bore (mm)	L (min-max, mm)	F (mm)	G (min-max, mm)	T (Polypropylene, mm)
50	73.7 - 76.2	36.3	6.4 - 12.7	3.8
100	99.6 - 102.1	49.3	6.4 - 12.7	4.6
150	99.6 - 102.1	49.3	6.4 - 12.7	6.9

4. Notes:

3Materials▼

IS 11925 - Materials: Key Formulas, Tables & Specifications

1. Material Specifications (Clause 6.3)

Polypropylene fittings: Black, isotactic polypropylene or copolymer.
Minimum body wall thickness as per Table 6 (not fully provided here).

2. Dimensional Tables

Parameter	Nominal Bore (mm)	50	75	100	125	150	200	225
Coupling Length, L (mm)	Min	73.7	86.9	99.6	99.6	99.6	127	127
	Max	76.2	89.4	102.1	102.1	102.1	129.5	129.5
Pipe Joint Length, F (mm)	±0.25 mm	36.3	42.9	49.3	49.3	49.3	63.0	63.0
Gap at Initial Contact, G (mm)	Min	6.4	6.4	6.4	6.4	6.4	9.4	12.7
	Max	12.7	12.7	12.7	12.7	12.7	22.0	25.4
Coupling Wall Thickness, T (Polypropylene, mm)	Min	3.8	4.1	4.6	5.3	6.9	9.1	9.1

Refer to Tables 3, 4, 5 for Snap Ring, O-Ring joints, and Spigot & Socket dimensions.

3. Test Requirements (Clause 7.1.7)

Nominal Bore (mm)	Span, S (mm)	Overall Length, L (mm)	Load at Rupture (kg)	Min Deflection (mm)

4General Requirements and Dimensions▼

IS 11925: General Requirements & Dimensions Summary

1. Pipe Dimensions (Clause 4.1.2, Table 1)

Nominal Bore (mm)	50	75	100	125	150	200	225
Min Internal Dia (mm)	50	75	100	125	150	200	225
Max Internal Dia (mm)	54	80	106	133	160	213	239

Pipes must have circular cross-section within these limits.

2. Taper Coupling Joints (Clause 5.2, Table 2)

Parameter	50	75	100	125	150	200	225
Coupling Length, L (min-max, mm)	73.7-76.2	86.9-89.4	99.6-102.1	99.6-102.1	99.6-102.1	127-129.5	127-129.5
Pipe Joint Length, F (±0.25 mm)	36.3	42.9	49.3	49.3	49.3	63.0	63.0
Gap at Initial Contact, G (min-max, mm)	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	9.4-22.0	12.7-25.4
Coupling Wall Thickness, T (Polypropylene, mm)	3.8	4.1	4.6	5.3	6.9	9.1	9.1

3. Snap Ring Joints (Clause 5.3, Table 3)

For nominal bores 75 to 150 mm.
Key dimensions include socket diameter (

5Joints and Couplings▼

IS 11925: Key Specifications for Joints and Couplings

1. Taper Coupling Joints (Clause 5.2, Table 2, Fig. 2)

Parameter	Nominal Bore (mm)	50	75	100	125	150	200	225
Coupling length, L (min-max)	mm	73.7-76.2	86.9-89.4	99.6-102.1	99.6-102.1	99.6-102.1	127-129.5	127-129.5
Pipe joint length, F (±0.25 mm)	mm	36.3	42.9	49.3	49.3	49.3	63.0	63.0
Gap at initial contact, G (min-max)	mm	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	9.4-22.0	12.7-25.4
Coupling wall thickness, T (Impregnated fibre, min)	mm	6.4	7.1	8.1	10.4	11.7	11.5	16.0
Coupling wall thickness, T (Polypropylene, min)	mm	3.8	4.1	4.6	5.3	6.9	9.1	9.1

2. Snap Ring Joints (Clause 5.3, Table 3, Fig. 3)

Parameter	Nominal Bore (mm)	75	100	125	150
Socket diameter, D1	mm	108.3	135.0	174.7	201.8
Throat diameter, D2	mm	98.7

6Fittings▼

IS 11925 - Key Specifications for Fittings

1. Material & Thickness (Clause 6.3, Table 6)

Material: Black polypropylene (homopolymer or copolymer) with stabilizers.
Body wall thickness (mm):

Nominal Bore (mm)	50	75	100	125	150	200	225
Below ground	3.5	3.5	4.0	5.2	5.2	7.0	7.0
Above ground	2.7	2.7	2.7	3.8	3.8	3.8	3.8

2. Taper Coupling Joints (Clause 5.2, Table 2)

Parameter	50	75	100	125	150	200	225
Coupling length, L (mm)	73.7-76.2	86.9-89.4	99.6-102.1	99.6-102.1	99.6-102.1	127.0-129.5	127.0-129.5
Pipe joint length, F (mm)	36.3	42.9	49.3	49.3	49.3	63.0	63.0
Gap at initial contact, G (mm)	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	9.4-22.0	12.7-25.4
Coupling wall thickness, T (impregnated fibre, mm)	6.4	7.1	8.1	10.4	11.7	11.5

7Test Requirements▼

IS 11925: Key Test Requirements Summary

1. Beam Strength & Deflection of Pipes (Clause 7.1.7)

Test machine speed: 13 mm/min
Test piece length (L): From Table 9 (see below)
Test conditions: 27 ± 2°C for 14 days prior
Setup: V blocks + central load via flexible strap (Fig. 10)
Acceptance:
- Deflection at rupture ≥ 5 mm
- Load at rupture ≥ specified load (Table 9)

Nominal Bore (mm)	Span S (mm)	Length L (mm)	Load (kg)
50	305	500	450
75	610	760	450
100	610	760	1000
125	610	760	1900
150	915	1070	2000
200	1220	1420	3175
225	1220	1420	4060

2. Resistance to Flattening (Clause 7.1.5)

Oven temp: 65 ± 1°C for 48 hours
Cooling: 1 hour at 27 ± 2°C
Acceptance: Diameter decrease ≤ 3% at load point

Nominal Bore (mm)	Test Load (kg)	Equivalent Load (kg/m)
50	25	167
75	25	167
100	25	167
125	29	194
150	29	194
200	36	240
225	36	240

3. Impact Test (Clause 7.2.1)

Specimen: Complete fitting, major axis horizontal

8Marking and Certification▼

IS 11925: Marking and Certification Key Points

1. Marking Requirements (Clause 8.1)

Pipes, couplings, and fittings for drainage must be marked with:
- Manufacturer's identification mark.
- Manufacturer's batch number.

2. BIS Certification Marking (Clause 8.2 & 8.2.1)

Use of the BIS Standard Mark is regulated by the Bureau of Indian Standards Act, 1986.
Manufacturers must obtain a license from BIS to use the Standard Mark.
Contact BIS regional or branch offices for licensing details.

3. Important Contact Information for BIS Offices

Region	Address & Phone Number
Central	Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi - 323 76 17, 323 48 41
Eastern	1/14 CIT Scheme VII M, V.I.P. Road, Calcutta - 337 86 62
Northern	SCO 335-336, Sector 34-A, Chandigarh - 60 38 43
Southern	C.I.T. Campus, IV Cross Road, Madras - 235 23 15
Western	Manakalaya, E9 MIDC, Marol, Andheri (East), Bombay - 832 92 95

(Branch offices and inspection points are also listed in the code for local support.)

Summary Table: Flattening Test Load (Clause 7.1.5)

Nominal Bore (mm)	Test Load (kg)	Equivalent Load (kg/m)
50	25	167
75	25	167
100	25	167
125	29	194
150	29	194
200	36	240
225	36	240

Notes:

Flattening test oven conditions: 65 ± 1°C for 48 hours.
Max allowable diameter decrease after test: 3%.

flowchart LR

9Annexures (if any)▼

IS 11925 Annexures: Key Tables & Specifications Summary

The standard provides detailed dimensional tables for various joint types and fittings used in polypropylene piping systems:

1. Table 2: Taper Coupling Joints (Clause 5.2)

Parameter	Nominal Bore (mm)	50	75	100	125	150	200	225
Coupling length, L (min-max)	mm	73.7-76.2	86.9-89.4	99.6-102.1	99.6-102.1	99.6-102.1	127-129.5	127-129.5
Pipe joint length, F	mm	36.3	42.9	49.3	49.3	49.3	63.0	63.0
Gap at initial contact, G	mm	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	6.4-12.7	9.4-22.0	12.7-25.4
Coupling wall thickness, T (polypropylene tapered ends)	mm	3.8	4.1	4.6	5.3	6.9	9.1	9.1

2. Table 3: Snap Ring Joints (Clause 5.3)

Parameter	Nominal Bore (mm)	75	100	125	150
Socket diameter, D1	mm	108.3	135.0	174.7	201.8
Throat diameter, D2	mm	98.7	125.4	159.6	186.3
Distance register, D3	mm	86.4	114.3	132.4	167.6
Insertion depth, L1

Frequently Asked

Popular Questions About IS 11925

?What materials are specified for pitch impregnation in fibre pipes under IS 11925?▼

According to IS 11925 (1986) for pitch-impregnated fibre pipes:

The pipe material is a preformed felted fibrous structure.
This fibrous structure is impregnated with pitch, bitumen, or other equally suitable compounds.
These materials must conform to the requirements specified in Clause 7 of the standard (not provided here but typically includes properties like penetration, softening point, and durability).

Summary:

Material for Impregnation	Purpose
Pitch	Waterproofing & durability
Bitumen	Alternative to pitch
Other suitable compounds	Must meet performance criteria

This impregnation ensures resistance to moisture and chemical attack for drainage pipes.

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?Which types of joints are covered and how do they ensure water-tightness?▼

Types of Joints Covered in IS 11925 and Water-Tightness Assurance

Joints covered:
- Soil Pipe 'O' Ring Joints (Clause 5.4): Telescopic joints using rubber 'O' rings complying with IS 5382-1969.
- Snap Ring Joints (Clause 5.3): Use snap rings for sealing.
- Spigot and Socket or Rebated Joints (Clause 5.5): Have rebates at midwall thickness to improve sealing.
- Other joints in Clauses 5.2, 5.3, 5.4 must pass water-tightness tests; joints in 5.5 and 5.6 are exempt.
Water-tightness ensured by:
- Use of 'O' rings or snap rings that conform to IS 5382-1969.
- Hydrostatic testing under 6 m water head for 1 hour without leakage (Clause 7.3):
  - Static head test for fixed joints.
  - Straight draw test for telescopic joints (axial extension of 10 mm).
  - Deflection test with angular displacement (up to 45 mm/m for small pipes).
  - Shear resistance test under pressure.
- Joints are firmly held but allow axial/horizontal movement during testing to simulate field conditions.

Summary Table of Tests for Water-Tightness (Clause 7.3)

Test Type	Condition	Requirement
Static Head Test	Fixed joint, 6 m water head, 1 hr	No leakage
Straight Draw Test	Telescopic joint, 10 mm axial extension	No leakage
Deflection Test	Angular deflection (45 mm/m or 25 mm/m)	No leakage
Shear Resistance Test	Under 6 m water head	No leakage

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?What mechanical tests are required to verify pipe and fitting strength?▼

Mechanical Tests to Verify Pipe and Fitting Strength as per IS 11925

Crushing Strength Tests (Clause 7.1.6)
- Test pieces (300 mm length for pipes; entire coupling/fitting tested) are crushed horizontally between flat plates at 13 mm/min.
- Conditioning:
  - Dry: 24 hrs at 27 ± 2℃ in air.
  - Wet: 24 hrs immersion in water at 27 ± 2℃, tested within 30 mins of removal.
  - Kerosene resistance: 10 days immersion in kerosene (boiling range 150-270℃), tested within 30 mins of removal.
- Load at rupture must meet or exceed values in Table 8 (e.g., 500 kg for 50 mm pipe length).
Joint Tests (Clause 7.3)
- Static Head Test: Joints withstand 6 m water head pressure for 1 hour without leakage.
- Straight Draw Test (Telescopic Joints): Must hold 6 m water head while extended axially 10 mm for 1 hour.
- Deflection Test: Joints withstand 6 m water head under angular deflection (45 mm/m for ≤150 mm bore; 25 mm/m for ≥200 mm bore).
- Shear Resistance Test: Joints withstand 6 m water head under shear forces.
Weld Line Tensile Strength (Clause 7.2.2)
- Socket ring cut from fitting is driven axially over a steel plug gauge the specified distance without fracture (see Table 10).

Key Tables Extract

Nominal Bore (mm)	Crushing Load (kg) Pipe	Coupling Load (kg)	Weld Line Drive Distance (mm)
50	500	122	25
75	500	143	32
100	500	169	38
125	590	195	38
150	590	195	47
200	725	304	50

?How does the standard address chemical resistance of pipes and fittings?▼

IS 11925 addresses chemical resistance of pitch impregnated fibre pipes and fittings mainly through conditioning and testing under aggressive environments:

Clause 7.1.6 (Crushing Strength Tests) includes a Resistance to Kerosene test:
- Test pieces immersed in kerosene (boiling range 150-270℃) for 10 days.
- After removal, load at rupture must meet minimum values in Table 8.
- This simulates chemical exposure and ensures mechanical integrity post-exposure.
Clause 6.2 (Fittings Fabrication):
- Adhesives used must be at least as chemically resistant as the pipe material.
- They must pass tests for chemical attack and boiling water resistance (Clause 7.1.8).
Clause 7.1.4 (Heat Resistance):
- Pipes/fittings heated at 80±1℃ for 8 hours should show no distortion or impregnant exudation, indicating stability under thermal and chemical stress.

Summary:

Chemical resistance is verified by immersion in kerosene for 10 days and subsequent mechanical testing.
Adhesives and fabrication methods must maintain chemical resistance.
Heat stability tests ensure no degradation under elevated temperature.

This ensures pipes and fittings maintain strength and integrity under chemical exposure typical in drainage applications.

?What are the dimensional tolerances for pipes and couplings according to this standard?▼

According to IS 11925, the dimensional tolerances for pipes and couplings are as follows:

Pipes:

Length tolerance: Maximum deviation of ±10 mm per meter measured on the inside curve using a 1 m straight edge (Clause 4.1.1).

Couplings (from Tables 2 to 5):

Parameter	Tolerance/Dimension Details
Coupling length, L	Varies by nominal bore (e.g., 50 mm bore: 73.7 to 76.2 mm)
Pipe joint length, F	Tolerance of ±0.25 mm
Gap at initial contact, G	Varies by bore (e.g., 50 mm bore: 6.4 to 12.7 mm)
Coupling wall thickness, T (polypropylene)	Minimum values given per bore (e.g., 50 mm bore: 3.8 mm)
Spigot length, F	Tolerance of +2.5 mm (e.g., 50 mm bore: 19 mm length)
Snap ring joint dimensions	Specific diameters and thicknesses per bore (see Table 3)
O-ring joint dimensions	Specific groove widths, coupling thickness, etc. (Table 4)

Summary:

Coupling and pipe joint dimensions have strict minimum and maximum limits varying by nominal bore.
Tolerances are explicitly given for pipe joint length (±0.25 mm) and spigot length (+2.5 mm).
Wall thickness and diameters have minimum specified values for structural integrity.

Example: Coupling length for 100 mm bore pipe

Minimum: 99.6 mm
Maximum: 102.1 mm

This ensures proper fit, sealing, and mechanical performance as per IS 11925.

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Nominal Bore (mm)	Crushing Load (kg) Pipe	Coupling Load (kg)	Weld Line Drive Distance (mm)
50	500	122	25
75	500	143	32
100	500	169	38
125	590	195	38
150	590	195	47
200	725	304	50

Nominal Bore (mm)	Crushing Load (kg) Pipe	Coupling Load (kg)	Weld Line Drive Distance (mm)
50	500	122	25
75	500	143	32
100	500	169	38
125	590	195	38
150	590	195	47
200	725	304	50

pitch-impregnated fibre pipes and fittings for drainage purposes

What This Standard Covers

Who Uses This Standard

Key Topics Covered

Table of Contents

Key Tables Summary:

Example: Taper Coupling Joint Dimensions (Table 2)

IS 11925 - Scope: Key Specifications & Tables Summary

Key Tables & Specifications:

1. Material & Fittings (Clause 6.3)

2. Pipe Dimensions (Clause 4.1.2, Table 1)

3. Taper Coupling Joints (Table 2)

4. Snap Ring Joints (Table 3)

5. O-Ring Joints (Table 4)

1. Definitions (Clause 2.0)

2. Important Tables Summary

3. Example: Taper Coupling Joint Dimensions (Table 2)

4. Notes:

1. Material Specifications (Clause 6.3)

2. Dimensional Tables

3. Test Requirements (Clause 7.1.7)

IS 11925: General Requirements & Dimensions Summary

1. Pipe Dimensions (Clause 4.1.2, Table 1)

2. Taper Coupling Joints (Clause 5.2, Table 2)

3. Snap Ring Joints (Clause 5.3, Table 3)

1. Taper Coupling Joints (Clause 5.2, Table 2, Fig. 2)

2. Snap Ring Joints (Clause 5.3, Table 3, Fig. 3)

1. Material & Thickness (Clause 6.3, Table 6)

2. Taper Coupling Joints (Clause 5.2, Table 2)

1. Beam Strength & Deflection of Pipes (Clause 7.1.7)

2. Resistance to Flattening (Clause 7.1.5)

3. Impact Test (Clause 7.2.1)

IS 11925: Marking and Certification Key Points

1. Marking Requirements (Clause 8.1)

2. BIS Certification Marking (Clause 8.2 & 8.2.1)

3. Important Contact Information for BIS Offices

Summary Table: Flattening Test Load (Clause 7.1.5)

Notes:

1. Table 2: Taper Coupling Joints (Clause 5.2)

2. Table 3: Snap Ring Joints (Clause 5.3)

Popular Questions About IS 11925

Summary:

Summary Table of Tests for Water-Tightness (Clause 7.3)

Key Tables Extract

Summary:

Pipes:

Couplings (from Tables 2 to 5):

Summary:

Example: Coupling length for 100 mm bore pipe

Need Detailed Clause Answers?

Nominal Bore (mm)	Crushing Load (kg) Pipe	Coupling Load (kg)	Weld Line Drive Distance (mm)
50	500	122	25
75	500	143	32
100	500	169	38
125	590	195	38
150	590	195	47
200	725	304	50