CPVC vs UPVC vs PVC: which pipe belongs where in an Indian home

Three plastics dominate Indian plumbing, their names differ by a single letter, and using the wrong one puts a failure inside your wall that you will not discover until the plaster is stained. Here is what each is actually for.

The one-line answer

CPVC — the hot water pipe

CPVC is PVC that has been chlorinated further, and that extra chlorine is what lets it hold its strength at temperature. Rated for continuous service around 93°C, it is the correct material for every supply line in a home that carries hot water — and it is perfectly good for cold lines too, which is why many builders simply run CPVC throughout for simplicity.

CPVC is joined with solvent cement, which does not glue the pipe so much as chemically fuse it: the solvent softens both surfaces and they cure into a single piece. Done properly, the joint is stronger than the pipe. Done in a hurry, it is the leak.

Sizing: SDR and CTS

Residential CPVC in India is usually sold to CTS (Copper Tube Size) dimensions in SDR 11. SDR is the ratio of outer diameter to wall thickness — lower means thicker wall and higher pressure rating. For a typical home:

• ½ inch (15 mm): individual fixture connections — basin, WC, health faucet
• ¾ inch (20 mm): branch lines feeding a bathroom, and most geyser connections
• 1 inch (25 mm): main down-take from the overhead tank

UPVC — cold water only

UPVC is “unplasticised” PVC: rigid, strong, corrosion-proof and cheaper than CPVC. It is excellent for cold water supply, borewell lines and tank connections.

The rule that matters: never put hot water through UPVC. Above roughly 60°C it begins to soften and loses the pressure-bearing strength the joint depends on. The failure is rarely dramatic — it is a slow weep at a fitting behind tiling, discovered as a damp patch months later.

PVC — drainage and waste

Ordinary PVC handles everything that flows by gravity rather than pressure: soil lines, waste lines and vents. Common sizes are 110 mm for the WC soil line and 75 mm for floor traps and basin waste.

The thing that actually determines whether drainage works is not the pipe but the fall. Aim for roughly a 1:40 to 1:60 gradient on horizontal runs. Too flat and solids settle; too steep and water outruns the solids, which is equally blocking.

Getting solvent-cement joints right

Most CPVC failures are installation failures, not material failures. The sequence that works:

1. Cut square. Use a proper pipe cutter, not a hacksaw. An angled cut reduces the bonding surface.
2. Deburr and clean. Remove the burr inside and out, and wipe both surfaces dry.
3. Apply cement to both surfaces — a thin even coat on the fitting socket, a slightly heavier one on the pipe end.
4. Insert with a quarter turn and hold for 30 seconds. The joint will try to push apart before it grabs.
5. Wait before pressure testing. Cure time depends on ambient temperature and pipe size — follow the manufacturer’s table. In Udaipur’s summer heat cure is faster; in winter it needs longer than people assume.

Use the solvent cement specified for the pipe you are joining. CPVC cement and PVC cement are not interchangeable.

Two things that specifically matter in Udaipur

UV exposure on terrace runs

Most Udaipur homes feed from an overhead tank, which means a length of pipe sits on the terrace in full sun. Sustained UV makes CPVC brittle over years. Paint exposed runs with a light-coloured acrylic paint, lag them, or route them inside a duct. This is cheap at installation and annoying to retrofit.

Low-pressure gravity systems

An overhead tank gives you roughly 0.1 bar per metre of height, so a typical rooftop tank produces far less pressure than a pumped mains supply. Two consequences: do not undersize the down-take line, and check the minimum pressure requirement before buying a rain shower or a thermostatic diverter — several need more pressure than a gravity system delivers. We cover this in our guide to choosing CP fittings.

Quick reference

We stock Astral and Ashirvad CPVC, UPVC and PVC systems along with the matching fittings and solvent cements at our Hiran Magri showroom. Bring your plumber’s list and we will check the sizes and quantities with you — see pipes and water tanks.