Materials
Materials tests properties, standards and selection of pipe and fitting materials for cold water, hot water, drainage and underground service. Marks come from matching material to temperature, pressure, soil condition and jointing method.
Common materials
- GI steel (IS 1239): strong, threaded, suitable for cold water; zinc coating resists corrosion but can scale.
- Copper: corrosion-resistant, handles hot water, joined by brazing or compression; avoid dissimilar metal contact.
- PVC-U (IS 4985): cold water and drainage, solvent-cemented; not for hot water above about 60 °C.
- CPVC: hot and cold water up to about 93 °C, solvent-cemented; needs closer support spacing.
- PPR: hot/cold water, heat-fusion joint; good chemical resistance.
- HDPE: underground and buried mains, butt-fusion or electrofusion; flexible and UV-sensitive.
- Cast iron: soil and waste stacks, good noise reduction, heavy.
Worked example
A solar hot-water line reaches 70 °C. PVC-U is unsuitable because it softens near 60 °C. Select CPVC or PPR, confirm the pressure rating at 70 °C, and use the manufacturer's solvent cement or fusion procedure. Do not simply choose the cheapest PVC pipe.
Traps
Using PVC on hot water, mixing PVC and CPVC fittings, leaving HDPE exposed to sunlight, or joining copper to GI without a dielectric union are common errors. Check the ISI mark and pressure class, not just the diameter.