Jindal Pipe Class A, B, C — Light, Medium & Heavy
Three classes to IS:1239, one difference between them: wall thickness. The outside diameter is the same, so the class you choose changes the weight, the pressure margin and where the pipe is accepted — not the fitting.
To IS:1239, across 15MM to 150MM, Jindal pipe comes in three classes that differ only in wall thickness at a fixed outside diameter: Light (Class A) is thinnest, Medium (Class B) is the general-purpose standard, and Heavy (Class C) is thickest for higher-pressure and structural use. Light equals A, Medium equals B, Heavy equals C.
The classes are defined by IS:1239, so they are identical for Jindal Star and Jindal Hissar. The wall thicknesses here are cross-checked against stock at the Delhi warehouse of Vijay Sales Corporation, supplied pan-India.
What Actually Changes Between the Classes
IS:1239 defines three classes for each pipe size, and the only thing that changes between them is the wall thickness. The outside diameter is held constant, so a Light, a Medium and a Heavy pipe of the same size all take the same fittings, threads and sockets — you cannot tell them apart by the outside. What the thicker wall buys is a higher pressure margin and more metal to corrode through before failure; what it costs is weight, and a slightly smaller bore.
The naming is where most of the confusion sits, because two systems describe the same three classes. Light is Class A, Medium is Class B, and Heavy is Class C. A drawing that calls for “Class B” and one that calls for “Medium” are asking for the same pipe. Both names appear on Jindal pipe and in Indian specifications, so it is worth reading them as interchangeable.
A point that comes up on almost every order: A, B and C is trade language — what dealers, plumbers and BOQs say across the market. IS:1239 itself uses only Light, Medium and Heavy, so a Jindal mill test certificate will say Medium, never Class B. Clients regularly ask why the class letter is missing from the certificate; it is not missing — the certificate uses the standard's official term, and Medium is Class B. Match the certificate's word to the letter on the BOQ and the two documents agree.
Because the wall is the variable, the class also sets the weight — a Heavy pipe is heavier per metre than a Light one of the same size — and it sets the internal diameter, which narrows as the wall thickens. The weight per class is on the weight chart, and the outside-versus-internal diameter relationship is on the size chart.
Wall Thickness by Class — IS:1239
Wall thickness in millimetres for Light (A), Medium (B) and Heavy (C), 15MM to 150MM. The outside diameter is the same across the three — see the size chart for OD.
| Size (NB) | Inch | Light / Class A (mm) | Medium / Class B (mm) | Heavy / Class C (mm) |
|---|---|---|---|---|
| 15MM | ½″ | 2.0 | 2.6 | 3.2 |
| 20MM | ¾″ | 2.3 | 2.6 | 3.2 |
| 25MM | 1″ | 2.6 | 3.2 | 4.0 |
| 32MM | 1¼″ | 2.6 | 3.2 | 4.0 |
| 40MM | 1½″ | 2.9 | 3.2 | 4.0 |
| 50MM | 2″ | 2.9 | 3.6 | 4.5 |
| 65MM | 2½″ | 3.2 | 3.6 | 4.5 |
| 80MM | 3″ | 3.2 | 4.0 | 4.8 |
| 100MM | 4″ | 3.6 | 4.5 | 5.4 |
| 125MM | 5″ | 4.8 | — | 5.4 |
| 150MM | 6″ | — | 4.8 | 5.4 |
Wall thickness to IS:1239 (Part-1):2004. 125MM is not made in Medium and 150MM is not made in Light. Every class is hydro-tested at 51 kg/cm². The branded full chart with outside diameters and metres-per-tonne is on the Jindal Hissar technical page.
What Each Class Is For
Thinnest wall, light duty
The lightest of the three, for low-pressure and light-duty lines — internal water runs and general low-stress service where a full-weight pipe is not needed. Marked with a yellow class band.
The general-purpose standard
The everyday middle class, and the one most water and gas distribution is specified in. If a line is not called out as Light or Heavy, it is usually Medium. Marked with a blue class band.
Thickest wall, high duty
The heaviest wall, for higher-pressure lines, structural and load-bearing use, and anywhere extra strength or corrosion margin is wanted — fire lines are commonly specified here. Marked with a red class band.
All three classes are hydro-tested to the same 51 kg/cm² at the mill; the class governs the working-pressure margin and the service life, which is why it is treated as a design decision. When a pressure line is borderline, the usual guidance is to step up a class rather than down.
Which Class by Application
General guidance, not a specification — the class for any line is set by the drawing, the consultant and the applicable code.
- Plumbing & water supplyMedium (B) as the general standard; Light (A) for low-pressure internal runs.
- Fire-fighting lineCommonly Heavy (C) for the higher pressure and corrosion margin — build to the fire consultant's class.
- Structural & fabricationHeavy (C) where load-bearing; for pure structural work, IS:1161 tubes are the dedicated route.
- Gas & air linesMedium (B) is the common choice; step up where pressure or code requires.
- Borewell / casingNot an IS:1239 class question — water-well casing is a separate standard (IS:4270) with its own wall schedule.
- Not sure?Send the line and duty — the class will be read back against what the specification allows.
Weight per class is on the weight chart; hollow sections for structural work are on the section-pipe page.
Reading the Class — and Why Not to Downgrade It
The class is written on the pipe in two ways. The colour band is the quick read — yellow for Light, blue for Medium, red for Heavy — and the ISI marking states the class alongside the licence number. The band, the marking, the wall thickness and the mill test certificate should all agree; if the band says Medium but the wall measures Light, the material is wrong.
The commercial temptation is to substitute a lighter class to shave weight and cost, because the outside diameter is identical and the pipe looks the same. It is not the same. A lighter class has a thinner wall and a lower pressure margin, so using it where a heavier class is specified can fail inspection outright and, worse, put the line at risk in service. The class is a design decision made for a reason; any change to it belongs with the consultant, in writing, not at the counter. That is the honest position, and it is the one taken here.
Class A, B, C — FAQ
What is the difference between Class A, B and C pipe?
The class sets the wall thickness at a fixed outside diameter, to IS:1239. Class A (Light) is thinnest, Class B (Medium) is the general-purpose middle, Class C (Heavy) is thickest. OD, threads and fittings are the same across classes; only the wall, weight and pressure margin change.
Why does the Jindal test certificate say Medium and not B class?
The official IS:1239 terms are Light, Medium and Heavy, so a Jindal mill test certificate says Medium — not the trade letter B. A, B and C is market shorthand for exactly those three classes, so Medium and Class B are the same pipe. A certificate that says Medium fully satisfies a BOQ that calls for Class B; match the word to the letter and the two documents agree.
Which class pipe is used for plumbing?
Medium (Class B) is the general-purpose choice for most water and gas plumbing; Light (Class A) for low-pressure internal runs. The specification sets the class; on a borderline pressure line, step up rather than down.
What is IS:1239 Class B pipe?
Class B is Medium-class GI or MS pipe — the middle of the three wall thicknesses and the everyday water and gas standard. A 50MM Class B has a 3.6mm wall, against 2.9mm for Class A and 4.5mm for Class C.
Does a heavier class change the outside diameter?
No. The OD is fixed across classes so fittings and threads match; a heavier class adds wall inward, reducing the bore and raising the weight, but the outside stays the same.
How do I tell the class of a pipe?
By the colour band — yellow Light, blue Medium, red Heavy — which should agree with the wall thickness and the test certificate. The ISI marking also states the class.
Can I use a lighter class to save cost?
Only if the specification allows it. A thinner wall means a lower pressure margin, so substituting where a heavier class is specified can fail inspection and compromise the line. Confirm any change with the consultant in writing.
Which class for a fire-fighting line?
Fire lines are commonly Heavy (Class C) for the pressure and corrosion margin, but the exact class is set by the fire consultant and the code. Build to the class the specification names.
Not Sure Which Class Your Line Needs?
List the line, the size and the duty — the class will be read back against what the specification allows.
Vijay Sales Corporation — certified dealer of Jindal Star and Jindal Hissar, stocking at its Delhi warehouse for pan-India supply. This is a reference guide; it carries no prices — see the Jindal Hissar and Jindal Star price lists.
Registered offices: 803 International Trade Tower, Nehru Place, New Delhi-110019 · 3356 Hauz Qazi, Delhi-110006.
GSTIN: 07AAGPG5324D1Z6 · Udyam (MSME) Reg: UDYAM-DL-01-0005438.
Methodology: Light/Medium/Heavy = Class A/B/C per IS:1239 (Part-1):2004; wall thicknesses are standard-fixed and identical across compliant makers. Application notes are general guidance and defer to the project specification.