PVC pipe sizing in India mixes inches, millimetres and pressure classes. This one guide gives you the full conversion chart, wall thickness and application table you will need on site.
PVC pipe sizing in India confuses everyone at least once. The trade quotes in inches, drawings specify millimetres, and the pipe wall thickness varies with pressure class. Bringing all three together is the single most useful reference an engineer, plumber or purchase manager can keep. This guide is that reference.
Inch and mm Nominal Size Conversion
PVC pressure pipes in India are named by nominal size in inches but manufactured by outer diameter in millimetres. The two do not match arithmetically — an inch here is a trade name, not a measurement.
| Nominal (inch) | Outer Diameter (mm) | Common Use |
|---|---|---|
| 1/2 inch | 20 | Small branch lines |
| 3/4 inch | 25 | Fixture feeds |
| 1 inch | 32 | Bathroom mains |
| 1-1/4 inch | 40 | Kitchen mains |
| 1-1/2 inch | 50 | Floor mains |
| 2 inch | 63 | Riser / building main |
| 2-1/2 inch | 75 | Terrace tank inlet |
| 3 inch | 90 | Underground service |
| 4 inch | 110 | Sewer / large service |
| 5 inch | 140 | Estate distribution |
| 6 inch | 160 | Estate mains |
| 8 inch | 200 | Municipal / lift irrigation |
| 10 inch | 250 | Trunk main |
Pressure Classes Under IS 4985
IS 4985 defines six pressure classes based on working pressure at 27 degC. Higher class = higher pressure rating = thicker wall.
| Class | Working Pressure | Typical Application |
|---|---|---|
| Class 1 | 2.5 kgf/cm2 | Gravity feed, low-pressure agri |
| Class 2 | 4 kgf/cm2 | Terrace tank fed cold water |
| Class 3 | 6 kgf/cm2 | General building supply |
| Class 4 | 8 kgf/cm2 | Pumped supply, agri sprinkler |
| Class 5 | 10 kgf/cm2 | Boosted pressure lines |
| Class 6 | 12.5 kgf/cm2 | Industrial / lift rising mains |
Wall Thickness by Class — 90mm Example
For a 90 mm OD pipe, minimum wall thickness under IS 4985 is:
| Class | Min Wall Thickness (mm) | Approx Weight per 3m Pipe (kg) |
|---|---|---|
| Class 1 | 2.2 | 1.8 |
| Class 2 | 2.8 | 2.3 |
| Class 3 | 3.5 | 2.9 |
| Class 4 | 4.3 | 3.5 |
| Class 5 | 5.4 | 4.4 |
| Class 6 | 6.6 | 5.3 |
SWR and CPVC Size Systems Are Different
PVC SWR pipes (IS 13592) are named by nominal size that roughly matches OD — 75 mm SWR really is 75 mm OD.
CPVC pipes (IS 15778) use the copper tube size (CTS) system with a different OD chart. A 25 mm CPVC pipe has an OD of about 28.5 mm, not 25 mm.
Never assume interchangeability between PVC pressure, SWR and CPVC by nominal size — the OD systems are all different.
Which Size for Which Application
Bathroom cold-water branch: 1 inch (32 mm) Class 3.
Kitchen main: 1-1/4 inch (40 mm) Class 3.
Apartment floor main: 1-1/2 inch (50 mm) Class 3 or 4.
Building cold-water riser: 2 inch (63 mm) Class 4.
Terrace tank inlet from pump: 1-1/2 to 2 inch (50 to 63 mm) Class 3 or 4.
Farm sprinkler sub-main: 63 mm to 75 mm Class 3.
Farm main from pump: 90 mm to 140 mm Class 3 or 4.
Underground service line: 90 mm to 110 mm Class 4.
Standard Pipe Lengths
Standard IS 4985 pipe length is 3 metres for solvent-cement type and 6 metres for ring-fit socket type. Project-length 6 m pipes are available on order and reduce joint count by half — worth specifying for long main runs.
Frequently Asked Questions
What is the outer diameter of 1 inch PVC pipe in India?
1 inch nominal PVC pressure pipe to IS 4985 has an outer diameter of 32 mm. The inch designation is a trade name, not an actual measurement.
How do I convert inch PVC pipe sizes to mm?
Use the standard IS 4985 conversion: 1/2 inch = 20 mm, 3/4 inch = 25 mm, 1 inch = 32 mm, 1-1/4 inch = 40 mm, 1-1/2 inch = 50 mm, 2 inch = 63 mm. The relationship is by trade convention, not arithmetic.
What pressure class PVC pipe should I use for home plumbing?
Class 3 (6 kgf/cm2) is the default for gravity and boosted cold-water lines in Indian homes. For pumped mains and long risers, move to Class 4.
Are CPVC and PVC pipes the same size?
No. CPVC uses the Copper Tube Size (CTS) system with different outer diameters. A 25 mm CPVC pipe is about 28.5 mm OD — do not swap fittings between CPVC and PVC by nominal size.
Reviewed by
Sahil Jindal
Managing Director, Jindal Composite Tubes Pvt Ltd
3rd-generation pipe manufacturer with 25+ years of hands-on experience in PVC, CPVC and UPVC pipe engineering, ISI/BIS compliance and India-wide plumbing distribution.