Thermal Expansion Coefficient of PVC

PVC moves 5.4 mm per 100 m per degree — a 30 m buried or suspended run swinging 30 °C changes length by 49 mm. Installers who lay PVC tight between two rigid anchors on a cool morning discover this the first hot afternoon, as the pipe snakes, lifts hangers, or shears at a fitting. Every plastic-pipe manufacturer publishes offset-leg and expansion-loop tables, and they are longer than the steel equivalents for the same movement because PVC is also far more flexible.

Two more traps come with the territory. PVC's modulus is only about 3 GPa, so restrained thermal stress is modest (E α ΔT is roughly 160 kPa per degree) but buckling and sagging are not — support spacing must be halved at elevated temperature, and PVC's pressure rating derates sharply above 23 °C, reaching about 20 % of nominal at 60 °C. CPVC and PEX behave differently again (PEX is even more expansive but flexible enough to absorb it). Never treat a plastic pipe schedule as a metal one with a different wall thickness.