PVC Pipe Pressure Class: 4 kg vs 6 kg vs 10 kg, and Which to Buy
Plumbing Guides
PVC Pipe Pressure Class: 4 kg vs 6 kg vs 10 kg, and Which to Buy
11 min read
Quick answer: The kg figure on a PVC pressure pipe is its working pressure at 27°C under IS 4985. A 4 kg pipe is Class 2, rated 0.4 MPa or about 40 metres of water head. A 6 kg pipe is Class 3, rated 0.6 MPa or about 60 metres, and a 10 kg pipe (Class 5) takes about 100 metres. In 110 mm Supreme, the 4 kg pipe is ₹1,199 (list ₹2,067) and the 6 kg pipe ₹1,785 (list ₹3,077) per pipe, before GST, checked on 3 November 2026.
Most people who ask us this are laying a line outside the house: borewell to sump, sump to a tank on a stand, or a main across a farm or a plantation. The pipes look the same on the rack, the 6 kg costs about half as much again as the 4 kg, and the temptation is to buy the cheaper one. This page explains what the number means, how to work out which class a line needs, and what each class costs in Supreme today.
What the kg number on a PVC pipe means
Unplasticised PVC pressure pipe for water in India is made to IS 4985. The standard sorts pipe into six classes by working pressure at 27°C, and the kg figure your plumber uses is that working pressure written in kg/cm² (you will also see kgf/cm², which is the same unit). The table below is from clause 5.1 of IS 4985:2000. The print colour is the one the 2007 amendment to that edition sets for each class.
| Class | Working pressure | In kg/cm² | Roughly, metres of water head | Print colour |
|---|---|---|---|---|
| Class 1 | 0.25 MPa | 2.5 | 25 m | Red |
| Class 2 | 0.4 MPa | 4 | 40 m | Blue |
| Class 3 | 0.6 MPa | 6 | 60 m | Green |
| Class 4 | 0.8 MPa | 8 | 80 m | Brown |
| Class 5 | 1.0 MPa | 10 | 100 m | Yellow |
| Class 6 | 1.25 MPa | 12.5 | 125 m | Black |
The head column is simple arithmetic. A column of water 10 metres tall presses down with 1 kg/cm² at its foot, so every 1 kg of rating is about 10 metres of head. Pump makers rate pumps in metres of head, which is why we convert: a pump with a 40 metre maximum head can put about 4 kg/cm² into a pipe.
Three details from the standard that matter on site:
- The class changes the wall, not the outside. A 110 mm pipe is 110 mm outside in every class. A higher class has a thicker wall, so it is heavier, dearer and has a slightly smaller bore.
- The rating is at 27°C. IS 4985 recommends these pipes for water from 1°C to 45°C, and says the working pressure must be reduced above 27°C using a derating graph in the standard. It also says an occasional summer rise during the day, with cooler nights, does no harm over the life of the pipe. A pipe lying in the sun all day is a different matter, so bury it or shade it.
- Agriculture is covered. Amendment 1 of 2006 added the line "These pipes can be used for agricultural uses also." The pipes sold as agriculture pipes are the same IS 4985 pipes. Casing pipe for the borewell itself is a separate product under a different standard.
Supreme states that its agriculture pressure pipe is made to IS 4985:2000 in PN 2.5 to PN 12.5, from 20 mm to 450 mm, with solvent cement and rubber ring joints, and that its moulded fittings conform to IS 7834.
How to work out which class a line needs
The question is not how high the water goes. It is the highest pressure the pipe will ever see, at its most stressed point. Three things set it:
- The pump's maximum head. Every pump has a shut-off head, the head it develops when water cannot flow because a valve is shut or the line is blocked. It is on the nameplate or in the maker's curve. That is the pressure a pipe near the pump sees when someone closes a valve at the far end.
- Any fall along the route. Every 10 metres the line drops below the pump adds about 1 kg/cm² at the low point. A main that runs downhill to a lower field needs a higher class at the bottom than at the top.
- Surge. When a pump starts or stops, or a valve is slammed shut, pressure spikes above the steady figure. Leave margin above the first two numbers rather than buying a pipe rated exactly at them.
Then pick the next class up. That is all the method is. The jobs below are the ones we are asked about most, with the class we usually suggest. Treat these as a counter opinion, and check them against your own pump's figures.
| Job | What sets the pressure | What we usually suggest |
|---|---|---|
| Gravity line from a tank on a stand or a terrace | The height of the water above the outlet. A tank 6 m up gives about 0.6 kg/cm². | Any class covers the pressure. We suggest 4 kg for buried runs of 63 mm and above, because the 2.5 kg pipe has the thinnest wall and the least margin for a careless backfill. |
| Sump to overhead tank, run outside the building | The pump's shut-off head, which is far above the few metres of lift. | 6 kg at 40 and 50 mm. In 20 to 32 mm the lowest class in our Supreme range is 10 kg, which settles it. |
| Borewell delivery, from the well head to a sump or field | Shut-off head of the submersible minus the depth of the water level in the bore. | 10 kg near the well head unless you have done the sum below and it comes out comfortably under 6 kg. |
| Farm irrigation main | Pump head plus any fall to the lowest field, plus surge. | 6 kg on level ground with a modest pump; 10 kg where the main runs downhill or the pump is strong. |
| Sub-mains and laterals after a valve or tank | The reduced pressure downstream. | 4 kg is common; match it to the actual pressure. |
The borewell sum, worked
Borewell lines catch people out because the surface pressure is not fixed. With the outlet valve shut, the pipe at the well head sees the pump's shut-off head minus the depth of the water level below ground. Take an example pump with a shut-off head of 180 m. If the water stands 150 m down, the surface pipe sees about 30 m, or 3 kg/cm². After a good monsoon the water level may rise to 100 m down, and the same pump now pushes about 80 m, or 8 kg/cm², into the same pipe. A 4 kg pipe that was fine in May is over its rating in October. Size for the highest water level you expect, not the lowest.
Inside the house, use CPVC or uPVC rather than IS 4985 agriculture pipe; we cover that choice in CPVC against PVC and CPVC against uPVC.
Supreme PVC pipe prices by class
These are our selling prices before GST, per pipe as supplied, with Supreme's list price alongside. Checked on 3 November 2026. IS 4985 allows effective lengths of 4, 5 or 6 metres, so check the length on the bill before you compare per-metre rates with another quote. Class 4 (8 kg) and Class 6 (12.5 kg) are not in our regular Supreme range; we quote them on request. A dash means that class is not in our range in that size.
Small sizes, 20 to 50 mm
| Outside diameter | 2.5 kg (Class 1) | 4 kg (Class 2) | 6 kg (Class 3) | 10 kg (Class 5) |
|---|---|---|---|---|
| 20 mm | – | – | – | ₹113 (list ₹195) |
| 25 mm | – | – | – | ₹175 (list ₹302) |
| 32 mm | – | – | – | ₹277 (list ₹477) |
| 40 mm | – | – | ₹247 (list ₹426) | ₹431 (list ₹743) |
| 50 mm | – | – | ₹380 (list ₹656) | ₹670 (list ₹1,156) |
Mains, 63 to 160 mm
| Outside diameter | 2.5 kg (Class 1) | 4 kg (Class 2) | 6 kg (Class 3) | 10 kg (Class 5) |
|---|---|---|---|---|
| 63 mm | – | ₹432 (list ₹744) | ₹625 (list ₹1,078) | ₹1,015 (list ₹1,750) |
| 75 mm | – | ₹608 (list ₹1,049) | ₹873 (list ₹1,505) | ₹1,450 (list ₹2,500) |
| 90 mm | ₹599 (list ₹1,033) | ₹901 (list ₹1,553) | ₹1,320 (list ₹2,275) | ₹2,071 (list ₹3,571) |
| 110 mm | ₹930 (list ₹1,604) | ₹1,199 (list ₹2,067) | ₹1,785 (list ₹3,077) | ₹3,090 (list ₹5,327) |
| 125 mm | ₹1,202 (list ₹2,072) | ₹1,846 (list ₹3,183) | ₹2,655 (list ₹4,577) | – |
| 140 mm | ₹1,507 (list ₹2,599) | ₹2,194 (list ₹3,782) | ₹3,219 (list ₹5,550) | ₹5,043 (list ₹8,694) |
| 160 mm | ₹1,926 (list ₹3,321) | ₹2,692 (list ₹4,641) | ₹3,808 (list ₹6,566) | ₹6,512 (list ₹11,228) |
Read the 110 mm row across. Going from 4 kg to 6 kg adds ₹1,785 minus ₹1,199, or ₹586 a pipe. Going from 6 kg to 10 kg adds ₹1,305. On a pumped main that difference is small next to the cost of digging up a burst. On a gravity line it is money spent on pressure the pipe will never see. Sizes from 180 mm to 450 mm are on the Supreme price list page, and the full Supreme PVC range is set out in our Supreme PVC pipe price list for 2026.
From our shop
Products in this guide
Live dealer prices. Add to cart, or ask for a GST quote on the whole list.
Fittings: match or beat the pipe
A pipe is only as strong as its weakest fitting. Supreme labels its moulded agriculture fittings by pressure, and we stock elbows, tees and couplers in 3, 4, 6, 10 and 16 kg ranges. The rule is easy: the fitting's rating should be at or above the pipe's class. A 6 kg main with 4 kg elbows is a 4 kg main. Prices for the common irrigation sizes, before GST:
| Fitting | Size | 4 kg | 6 kg | 10 kg |
|---|---|---|---|---|
| Elbow | 63 mm | ₹41 (list ₹70.30) | ₹44 (list ₹75) | ₹49 (list ₹84.70) |
| Elbow | 75 mm | ₹56 (list ₹96) | ₹60 (list ₹104) | ₹74 (list ₹128) |
| Elbow | 90 mm | ₹82 (list ₹142) | ₹106 (list ₹183) | ₹127 (list ₹219) |
| Tee | 63 mm | ₹53 (list ₹91.30) | ₹60 (list ₹103) | ₹74 (list ₹127) |
| Tee | 75 mm | ₹73 (list ₹126) | ₹86 (list ₹148) | ₹103 (list ₹178) |
| Tee | 90 mm | ₹118 (list ₹203) | ₹130 (list ₹224) | ₹175 (list ₹302) |
| Coupler | 63 mm | ₹19 (list ₹33.60) | ₹23 (list ₹40.20) | ₹29 (list ₹50.10) |
| Coupler | 75 mm | ₹32 (list ₹55.40) | ₹35 (list ₹60.50) | ₹45 (list ₹78.40) |
| Coupler | 90 mm | ₹46 (list ₹78.90) | ₹56 (list ₹96) | ₹68 (list ₹118) |
For threaded connections at a pump or valve, Supreme makes male and female threaded adaptors in the same kg ranges, for example the 63 mm 10 kg male threaded adaptor at ₹26 and female threaded adaptor at ₹37.
Mistakes we see with pressure pipe
- Buying on price per pipe for a pumped line. The lowest class made in your size is always the cheapest per pipe, which is exactly why it ends up on lines that need more.
- One class for the whole route. On a long main the class can step down after a valve or a break tank. It should not step down before the pump's full pressure has been relieved.
- Shutting a valve against a running pump. That puts the full shut-off head on the pipe. If the line must be closed with the pump running, the pipe has to be rated for it.
- Pipe left on the surface. Sun warms the pipe above the 27°C the rating assumes and weakens it over time. Bury mains, or shade them.
- The wrong cement. Use PVC solvent cement, not CPVC cement, and a heavier-bodied cement on the larger sizes. Supreme's PVC solvent cement, 250 ml is ₹245 (list ₹544) and the PVC heavy duty solvent, 250 ml is ₹181 (list ₹403). Rubber ring joints need lubricant, not cement: Supreme rubber lubricant, 250 g, ₹41 (list ₹91).
Once a line is laid, test it before you backfill. The same principles as a house test apply, scaled up; see our guide to pressure testing before you close it in.
Buying agriculture pipe from us
We stock Supreme PVC pressure pipe and fittings at the counter in Viveknagar, Bengaluru 560047. Send us the route length, the size, your pump's maximum head and, for a borewell, the water level, and we will check the class with you before you buy. Use the quote tool, WhatsApp +91 99801 00987, or come to the counter. For the tax on any of this, see PVC pipe HSN code and GST rate.
Questions we get asked
What is the difference between 4 kg and 6 kg PVC pipe?
Pressure rating and wall thickness. Under IS 4985 a 4 kg pipe (Class 2) is rated 0.4 MPa and a 6 kg pipe (Class 3) is rated 0.6 MPa at 27°C, about 40 m and 60 m of head. The outside diameter is the same, so they take the same size fittings, but the fittings should carry the same or higher rating.
Which class of PVC pipe is used for agriculture?
All of them, depending on the pressure. 4 kg and 6 kg are common for irrigation mains on level ground, and 10 kg near a strong pump or a borewell. Work it out from the pump's maximum head as shown above.
What is class 3 PVC pipe?
Class 3 under IS 4985 is the 0.6 MPa or 6 kg/cm² pipe, printed in green under the 2000 edition's marking rules.
Which PVC pipe is best for borewell delivery?
For the surface line from the well head, a class above the pump's shut-off head minus the shallowest water level you expect. Unless that sum comes out comfortably lower, we suggest 10 kg near the well head. The pipe inside the bore is a different product.
Pressure classes, colours and temperature limits on this page were checked against the IS 4985:2000 text and its amendments, and Supreme's product page, on 3 November 2026. Prices are our selling prices before GST on that date.