Which pipe for which job? uPVC, CPVC, SWR and HDPE explained

A hot water line run in uPVC will soften. A drainage stack built with thin-wall pipe will crack. A buried main sized without a surge margin will split at the first pump shutdown. Each of these is a specification mistake, not a manufacturing one.

There are four plastic pipes you will use most often. Each one does a different job. Here is how to tell them apart.

The short answer

• uPVC — cold water under pressure. Also irrigation, borewell casing and cable duct. Rigid, cheap, glued together with solvent cement.
• CPVC — hot and cold water. It is the only one of the four you can use for a geyser line.
• SWR — building drainage and venting. It carries waste by gravity, not under pressure.
• HDPE — buried mains and irrigation. Flexible, comes in coils, welded into a leak-free line.

uPVC pressure wall CPVC pressure wall SWR thin wall HDPE thick wall

Standard

IS 4985

Max temperature

~60°C

Under pressure

Yes — sold by class, 2.5 to 12.5 bar

Jointing

Solvent cement

Use it for

Cold water, irrigation, borewell casing, cable duct

Standard

IS 15778

Max temperature

~93°C

Under pressure

Yes — de-rates sharply as it heats

Jointing

CPVC cement (not PVC cement)

Use it for

Hot and cold plumbing, geyser and solar lines

Standard

IS 13592 (fittings IS 14735)

Max temperature

~60°C

Under pressure

No — gravity only

Jointing

Cement, or ring-fit on stacks

Use it for

Soil, waste and rainwater drainage, venting

Standard

IS 4984

Max temperature

~45°C

Under pressure

Yes — by SDR, roughly PN 6 to PN 16

Jointing

Heat fusion

Use it for

Buried mains, irrigation, directional drilling

Start with temperature

Temperature rules out options faster than anything else.

uPVC starts to soften at about 60°C. That makes it a cold-water material. Use it for cold supply, drainage and irrigation.

CPVC is the same plastic with extra chlorine added. That takes it to about 93°C. This is why CPVC goes on geyser lines, solar hot water and any indoor hot-and-cold plumbing.

There is a catch worth knowing. CPVC loses pressure capacity as it gets hotter. A CTS SDR 11 pipe handles around 27.5 bar at 23°C, but only around 6.9 bar at 82°C. Always check the rating at your actual working temperature, not the number on the front of the brochure.

HDPE for drinking water is rated for roughly 0–45°C, and it also de-rates as temperature climbs.

23° 38° 49° 60° 71° 82° 93°

27.5 bar CPVC CTS SDR 11 at 23°C — 100% of its 23°C rating uPVC and SWR still in range · HDPE still in range

22.6 bar CPVC CTS SDR 11 at 38°C — 82% of its 23°C rating uPVC and SWR still in range · HDPE still in range

17.9 bar CPVC CTS SDR 11 at 49°C — 65% of its 23°C rating uPVC and SWR still in range · HDPE past its limit

13.8 bar CPVC CTS SDR 11 at 60°C — 50% of its 23°C rating uPVC and SWR still in range · HDPE past its limit

11 bar CPVC CTS SDR 11 at 71°C — 40% of its 23°C rating uPVC and SWR past their limit · HDPE past its limit

6.9 bar CPVC CTS SDR 11 at 82°C — 25% of its 23°C rating uPVC and SWR past their limit · HDPE past its limit

5.5 bar CPVC CTS SDR 11 at 93°C — 20% of its 23°C rating uPVC and SWR past their limit · HDPE past its limit

Indicative, for CPVC CTS SDR 11 against the standard de-rating factors. Always size from the manufacturer’s table for the product you are buying.

Then check the pressure rating

You will see two systems on the pipe.

PN is the working pressure in bar. PN 10 means 10 bar. You will see this on metric uPVC and on HDPE.

Schedule is the American system — Schedule 40, 80, 120. For any given size, the outside diameter stays the same across all schedules. Only the wall gets thicker. That is why the same fitting works across all of them.

You will also see SDR on HDPE. It is the outside diameter divided by the wall thickness. A lower SDR means a thicker wall and more pressure. For PE100 water pipe: SDR 11 is roughly PN 16, SDR 17 is roughly PN 10, SDR 26 is roughly PN 6.

On a pumped line, go one SDR thicker than the calculation says. Pumps create surge when they shut down, and surge is what splits pipe.

Indian pressure classes on uPVC

uPVC drinking water pipe made to IS 4985 is sold by pressure class:

The class number is a pressure code, not a size. Class 5 is the 10-bar pipe. Sizes usually run from 20 mm to 315 mm, in 6 metre lengths.

SWR is not a pressure pipe

SWR stands for Soil, Waste and Rainwater. It is uPVC, but made to IS 13592, with fittings to IS 14735. It moves waste downhill by gravity and vents foul gas. It holds no pressure at all.

It comes in two wall grades:

• Type A — thinner. For vent pipes and rainwater downtakes.
• Type B — thicker. For soil and waste stacks.

Common sizes are 75, 90, 110 and 160 mm.

Type Athinner wall Type Bthicker wall

Type A — vents and rainwater. Vent pipes and rainwater downtakes, where nothing but air and rain passes through.

Type B — soil and waste. Soil and waste stacks. Do not substitute Type A here to save money; on vertical stacks use ring-fit joints so the pipe can move.

Common sizes 75, 90, 110 and 160 mm. Wall thickness per IS 13592 varies with diameter — ask the desk for the table against your sizes.

Do not swap Type B for Type A to save money. The wall thickness is the specification. On vertical stacks, use ring-fit joints rather than glued ones, so the pipe can expand and contract without stressing the joint.

HDPE, and when it beats PVC

HDPE wins where rigid pipe struggles. Long buried mains. Uneven ground. Irrigation across a field. Directional drilling under a road.

It comes in coils up to around 110 mm, and it is joined by heat fusion rather than glue. That makes the joint as strong as the pipe itself, which matters under a road where you cannot dig again.

The trade-offs are real: it costs more, it needs fusion equipment and a trained crew, and it will not bend as tightly as you might hope.

Side by side

Four mistakes to avoid

1. uPVC on a hot line. It will soften. Use CPVC.
2. PVC cement on CPVC. The two cements are different. CPVC needs its own cement and primer.
3. Ignoring heat on exposed runs. A rooftop line in the Gulf is not working at 20°C.
4. Mixing sizing systems. Metric and inch pipe will not seat in each other’s fittings.

Getting it specified correctly

Tell us four things — the fluid, the temperature, the working pressure and the size range — and we will quote the correct class, schedule or SDR for your project.

Hrivika Global supplies the full range of uPVC, CPVC, SWR and HDPE pipes and fittings from established Indian manufacturers, shipped worldwide from India.

Common questions