Material family
HDPE is a thermoplastic polyolefin. PVC is a chlorinated thermoplastic. HDPE is flexible; PVC is rigid. HDPE is unaffected by acids, alkalis and hydrocarbons; PVC is attacked by aromatic hydrocarbons and ketones.
Pressure ratings
HDPE: PN 2.5 to PN 16. PVC: up to PN 10 in standard grades. Both can be higher in specialty grades.
Temperature range
HDPE: 0°C to 40°C service (derates above). PVC: 0°C to 27°C. Neither is suited to sustained hot-water service; use PPR for that.
Joints
HDPE: heat-fusion (butt or electrofusion) — monolithic, zero-leak. PVC: solvent-cement or rubber-ring — depends on jointing quality.
Where each wins
HDPE for underground water, gas, industrial, telecom, mining. PVC for above-ground plumbing, agricultural laterals, borewell casing, cold-water plumbing.
